C/C++ Users Group Library 1996 July/C-C++ Users Group Library July 1996.iso/vol_300/318_02/sherlock.doc

Text File | 1990-06-16 | 96KB | 2,564 lines

SHERLOCK
C Programming Tool


February 1, 1990
Version 1.5


Edward K. Ream
1617 Monroe Street.
Madison, WI 53711



CHAPTER 1  INTRODUCING SHERLOCK


Welcome to Sherlock!  Sherlock is not an ordinary programming tool and
you may have some questions about it: what is it, what features does it
have, how does it operate, how will it benefit you, how do you use it, how
does it compare with other tools and techniques, how easy will it be to use,
how can you customize it?  This chapter poses and answers these kinds of
questions and along the way provides examples showing how to use
Sherlock.


What is Sherlock, anyway?

Sherlock is a debugging, tracing and profiling tool for the C programming
language.  That is, Sherlock allows you to test and debug C programs by
examining various traces.  As an added benefit, Sherlock offers detailed
statistics about your program.  Sherlock consists of C language macros
and support routines called by those macros.


Why should I use Sherlock?

Sherlock allows you to build, study, enhance and maintain more complex
programs in less time.  It gives you a better view of your program than
other kinds of debuggersDyou get more useful information and less
useless data.  Sherlock reveals your program at any level you wish, from a
global, overall, landscape view to a very detailed view.  And you get to choose the exact format in which the information is presented.  Sherlock
is very flexible and can be used with very large and complex programs,
including programs that use overlays and re-entrant programs.


How does Sherlock work?

The basic idea behind Sherlock is simple: you can create individual tracing
instructions, written in the C language, which lie dormant in your program
until enabled while your program is executing.


That sounds very simple.  What's the big deal?

The ability to add hide latent instructions inside a program and to enable
them while the program is running turns out to be very powerful.
Typically these dormant instructions are tracing statements such as print
statements.  By enabling various sets of these tracing instructions you can
produce literally thousands of different traces from your program without
changing it or recompiling it.  This is a very fast and handy way of
pinpointing the location of bugs, especially pointer bugs.


Isn't using Sherlock like putting print statements throughout a program?

Not really.  If you just insert print statements throughout your program
you are buried in useless output.  The sheer volume of the output hides the
information that would make a difference to you.  The only way to make
sense of the output is to get rid of most of it.  Alas, removing the print
statements and recompiling takes a lot of time.  Also, once print statements
have been removed they are not available later until they have been re-
inserted and and the program recompiled and relinked.  You just can't be
very flexible this way.

With Sherlock, you enable tracing statements without changing your
program in any way.  Generating different traces is done in a matter of
seconds, not minutes.  And since your program remains unchanged, bugs
remain stable;  their symptoms do not change as they would if you added
or deleted print statements.


How is it possible to enable or disable a single C instruction?

It's done with macros.  The instruction or instructions are entered as the
arguments to special tracing macros.  For instance, suppose you want to
disable the following print statement:

    printf("The value of i is %d\n", i);

The TRACE macro is one of several that you might use.  It takes two
arguments.  The first is the name that will be given to the disabled
statement, say "abc".  The second is the statement or statements we want to
disable.  The complete TRACE macro would look like this:

    TRACE("abc", printf("The value of i is %d\n", i));

Let's look at this carefully.  The name given to the print statement is
represented by the C string "abc".  The comma after the "abc" separates the
two arguments.  Next comes the printf statement and two right
parentheses, one for the printf statement and one for the TRACE macro.
Notice that the semicolon that ends the printf statement has been omitted.
It would also be all right to leave it in, like this:

    TRACE("abc", printf("The value of i is %d\n", i););

The effect of this macro is as follows: the print statement is executed when
control reaches the macro only if the symbol "abc" has already been
enabled.

Please note: the operation of the TRACE macro varies drastically from the
more traditional kind of debugging macros often used in programming
projects.  Sherlock macros enable or disable tracing code during the
execution of the program..  Traditional debugging macros require that the
program be recompiled in order to enable or disable the code in the macros
  The effect of this difference is enormous.


Can other kinds of statements besides print statements be used?

Yes.  You can disable any executable C statement or sequence of
statements, including blocks.  For instance, a very useful kind of tracing
statement might be a function call which would print out a complicated data
structure.


How do you tell Sherlock which macros you want to enable or disable?

The most common way is to add special arguments to the command line.
For instance, to enable any macro whose name is "abc" you would add the
following argument to the command line:

    ++abc

You can also enable macros while your program is running using other
Sherlock macros.

Won't the extra command line arguments interfere with my program?

No.  Sherlock removes these special arguments from the command line so
they will be completely invisible to your program.  They will not interfere
with the argument processing logic of your program in any way.


How does Sherlock know which arguments to delete from the command line?

All Sherlock arguments are preceded by one of two prefixes: an "on
prefix" that enables macros and an "off-prefix" that disables macros.  You
should choose each prefix to be something that will distinguish Sherlock
arguments from all other arguments to your program.  In the example
above, the prefix is ++.


Putting these macros into my programs seems like a lot of work to me.

Sherlock includes a utility program called SPP, for Sherlock Pre-Processor,
which will put macros at the entry and exit of all your functions
automatically, which is where you most often want them.


You mentioned that Sherlock is also a profiling tool.  What does that mean?

Sherlock gathers statistics automatically.  Sherlock counts how many times
each macro was encountered and also computes timing statistics using an
interrupt handler.  Sherlock associates these statistics with the names
defined by the macros.  All the details are handled by the macros.  You
may print a report of the statistics at any time.


How many Sherlock macros are there?

Over 30.


Why so many?

Many macros do the same basic thing with minor variations.  For instance,
 there is a TRACEP macro which is acts the same as TRACE except that
TRACEP prints its first argument, i.e., the name associated with the
macro, before executing the disabled instruction.  This saves some space in
your program.  There are also macros used to initialize the Sherlock
system, to enable or disable macros, and to print a report of statistics.


Must I remove all the macros when I am done debugging?

No.  You can simply undefine a single compile-time variable, recompile
and relink.  All the code generated by the macros will disappear and the
executable portion of your program will contain absolutely no evidence that
Sherlock macros exist in the source code. Thus, there is no need to
physically eliminate the macros from your source files.  There is a utility
program, called SDEL, which will remove Sherlock macros from a source
file if you want.


Can I choose different names for the Sherlock macros?

Yes.  All you have to do is to change names defined in a standard header
file.  You will still be able to use SPP and SDEL.  Both tools allow you to
specify alternate macro names to be used instead of the standard macro
names.


What if I want to change how the macros work?

Full source code is provided for all macros, support routines and utility
programs except SPP. To use the Sherlock system on another machine you
need only recompile the support routines on the new machines.  You will
need to rewrite the interrupt handler only if you wish to gather timing
statistics on the new machineDSherlock will work without the interrupt
handler.



CHAPTER 2  BEFORE USING SHERLOCK


This chapter provides information you should know before using
Sherlock.  It lists the hardware and software required, it reminds you to
create a backup copy of the distribution disk containing Sherlock, and it
lists the files that are distributed with the Sherlock system.


System Requirements

o An IBM PC/XT/AT computer or compatible with two floppy disks or a
hard disk.

o The MS-DOS operating system.

o Either the Microsoft C compiler or the Turbo C compiler.  Minor
modifications in Sherlock's source code will allow Sherlock to compile
using other C compilers.

o The Microsoft MASM macro assembler.  (Used only when changing the
interrupt handler.)


Backing Up Your Disks

Please back up the distribution disks before using Sherlock.  Use the DOS
COPY command to copy all the files on the distribution disks to backup
disks.  Your backup disks will be used as working disks.


Files on Your Disk

File        Description

read.me        Late breaking news and information.  Please read
        this file first.
*.mak        Make files for the Turbo C compiler version 1.5.
*.mmk        Make files for the Microsoft C compiler version
        5.00 or later.
*.lnk        Link files for the Turbo C linker.
*.ml        Link files for the Microsoft linker.
cpp.exe        C Preprocessor whose source code illustrates the
        use of Sherlock's macros.
\cpp\*.c    Source code for CPP.
\cpp\*.h    Header file for CPP.
dumpregs.c    C Language source code for a program illustrating
        the use of regs.asm.
prf.asm        Assembly language source code for the interrupt
        handler.
prfnear.obj    Object code for interrupt handlerDfor memory
        models with small code spaces.
prffar.obj    Object code for interrupt handlerDfor memory
        models with large code spaces.
regs.asm    Assembly language source code for the register
        dumper.
regsnear.obj    Object code for the register dumperDfor memory
        models with small code spaces.
regsfar.obj    Object code for the register dumperDfor memory
        models with large code spaces.
sdel.exe    Utility program which deletes all Sherlock macros
        from a single source file.
sdel.c        C language source code for SDEL illustrating the
        use of Sherlock's macros.
sdif.exe    Special purpose file comparison program.
sdif.c        The C language source code for SDIF.
sherlock.c    C language source code for support routines.
sl.h        Preferred definitions of macros.
sl1.h        Alternate definitions of macros.
spp.exe        Utility program which inserts Sherlock macros
        into a single source file.


Quick Start

This is the super-condensed version of the installation procedure.

1. Insert Sherlock macros into functions that you want to trace.  Sherlock
comes with a stand alone tool, called SPP, which will do this automatically
for you.  See the section called SPP of the User's Manual for details.

2. Insert the SL_INIT and SL_PARSE macros into your main() function as
the first executable statements.  Again, SPP will do this automatically for
you.

3.  Insert the line     #include "sl.h"   in each source file containing a
Sherlock macro.  This can be done automatically using the -i option of
SPP.  Alternatively, if you have a single header file which is inserted in all
your source files, insert the line  #include "sl.h" in that header file.

4. Recompile all files which contain Sherlock macros.  Make sure to
#define the compile time symbol called SHERLOCK.  The easiest and best
way to do this is with a command line option to the compiler.

5. Compile the source code for the Sherlock support routines, located in
sherlock.c.  Make sure the memory model used when compiling the
support routines is the same as the memory model used when compiling
the rest of the files of your program.  Sample make and link files to
accomplish this step are included in the directory called sherlock.

6. Link the following files together to produce an executable version of
your program:

o All the .obj files produced by compiling the files of your program.
o The .obj file produced by compiling sherlock.c.
o One (and only one) of the following two files:  prffar.obj or prfnear.obj.

Note:  Use prffar.obj when using memory models that have a code space
larger than 64K.  Use prfnear when using memory models that have a code
space limited to 64K or less.

7. Run your program.  To enable traces, add Sherlock command line
arguments to your program's command line. For example, to enable
tracing of a function called f(), add the argument ++f to the command line.

8. When you are done debugging, recompile all your files which contain
Sherlock macros with the compile time constant SHERLOCK not
#define'd.  The code produced by the Sherlock macros will disappear.
Relink all those files to produce a production version of your program.  Do
not link in the .obj file produced by compiling sherlock.c.  Do not link in
either prffar.obj or prfnear.obj.



CHAPTER 3  USING SHERLOCK


This chapter contains a tutorial introduction to Sherlock.  It tells you
everything you need to know to start using Sherlock.  After an initial
overview, the various macros comprising Sherlock will be discussed in
detail, with numerous examples along the way.  The last section discusses
how to enable macros using command line arguments.  For some tips
about debugging C programs, see the next chapter.  For the most complete
information about any aspect of the Sherlock system, see chapter five.


Overview

The Sherlock system consists of three main parts: tracing macros, other
macros including initialization and statistics reporting macros and support
routines called by the macros.  The support routines form the "hidden
machinery" of the Sherlock system and will not be discussed further in this
overview.

Sherlock's tracing macros are the most visible and important part of the
Sherlock system.  These tracing macros allow you to create tracing
statements embedded throughout your program which can be enabled or
disabled without recompiling your program or changing the executable
image of your program in any way.  Tracing macros also provide a
framework for gathering statistics about your program.

Each tracing macro defines a tracepoint, a tracepoint name and a list of
tracepoint actions.  A tracepoint is simply the location of the macro, the
tracepoint name is a C language string which names the tracepoint and the
tracepoint actions consist of one or more executable C language statements
which are executed only if the tracepoint has been enabled.

Let's look at one kind of tracing macro, called TRACE.  The format of this
macro is:

    TRACE(tracepoint_name, tracepoint_actions);

In other words, this macro takes two arguments, a tracepoint name and a
list of tracepoint actions.  For example:

    TRACE("print_abc", printf("The value of abc is %d/n", abc));

Notice the two closing parentheses.  The first ends the printf statement and
the second ends the TRACE macro.  In this example, the tracepoint name is
a string

literal, namely "print_abc", and the tracepoint actions consists of the single
statement:

    printf("The value of abc is %d/n", abc);

The operation of this TRACE macro is straightforward: the print statement
will be executed only if the tracepoint named print_abc has been enabled.

Please note: the operation of the TRACE macro varies drastically from the
more traditional kind of debugging macros often used in programming
projects.  Sherlock macros enable or disable tracing code during the
execution of the program. Traditional debugging macros require that the
program be recompiled in order to enable or disable the code in the macros.
The effect of this difference is enormous.  With Sherlock, you can scatter
tracing macros throughout your program with no ill effects. With
traditional debugging macros, this strategy is simply not possible because
you would be buried in tracing output.

How are tracepoints enabled?  There are two ways: from the command line
using special Sherlock arguments or from within your program using
Sherlock macros.  In practice, the command line is most often used.
Sherlock arguments consist of a prefix followed by a tracepoint name.
There are two possible prefixes: an on_prefix which enables the following
tracepoint name and an off_prefix which disables the following tracepoint
name.  These prefixes are defined by an initialization macro called
SL_PARSE and should be chosen so that Sherlock arguments can be
distinguished from all other command line arguments.  The SL_PARSE
macro processes all Sherlock arguments and then deletes them from the
command line so that they will not interfere with the argument processing
logic of your program.

Any string may be used for these prefixes, and in this manual we will
assume that the on prefix is ++ and the off prefix is - -.  For example, to
enable tracing for the tracepoint named print_abc, the following command
line argument could be used:

    ++print_abc

Wildcard characters and other construction may be used in Sherlock
arguments.  See the section on command line arguments for more details.

To summarize, here are the steps to use Sherlock:

1. Insert Sherlock macros throughout your program.  This is easy because
Sherlock comes with a utility program called the Sherlock Preprocessor
(SPP)  which will insert tracing macros automatically at the beginning and
end of every function in a file.  The tracing macros created by SPP will
print the values of all arguments to functions as well as the value returned
from all functions.

2. The Sherlock macros are defined in a header file called sl.h.  Insert the
following statement in every file that contains a Sherlock macro:

    #include <sl.h>

The SPP program will insert this statement for you if you desire.

3. Compile the files containing the Sherlock macros as usual and link in the
support routines to create an executable version of your program.

4. Run your program and enable various tracepoints using Sherlock
command line arguments.  On successive runs, focus on important details
by enabling different tracepoints.

5. After debugging is complete, remove the code generated by Sherlock
macros.  You can do this without removing the macros themselves by
undefining the compile time constant called SHERLOCK and recompiling.
Absolutely no overhead from the Sherlock macros will remain in your
program.

6. Most people will want to leave Sherlock macros inside their source file
so that they may be reactivated later by redefining the SHERLOCK
constant and recompiling.  However, a utility called SDEL will remove all
Sherlock macros from a source file if you desire.

This concludes the overview of the Sherlock system.  The next sections
introduce you to all of the Sherlock macros and will discuss details
concerning Sherlock command line arguments, header files and statistics.


Initialization: SL_INIT, SL_PARSE, SL_ON, and SL_OFF

Right at the start of your program, Sherlock's support routines must be
initialized and the Sherlock arguments on the command line must be
processed and removed.

The SL_INIT macro initializes Sherlock's support routines.  This macro
must be executed before any other macro.  The best place for the SL_INIT
macro is the very first executable statement of the main() routine.  The SPP
program will insert the SL_INIT macro at that spot for you.  Note that the
name is all UPPER CASE, as are the names of all Sherlock macros.

In the language of the draft C standard, the SL_INIT macro, like all of the
Sherlock macros, is a "function-like" macro, which means that parentheses
are required after it even though the macro takes no arguments.  Like this:
SL_INIT();

The SL_PARSE macro enables or disables tracepoints by processing an
argument list vector.  Most often, the vector is simply the argv vector
passed by the operating system to the main() routine, but it doesn't have to
beDyou can set up your own if you want.  The SL_PARSE macro may be
called more than once, so you can enable or disable tracepoints from inside
your program as well as from the command line.  Typically, the
SL_PARSE macro should be placed immediately following the SL_INIT
macro in the main() routine.  Again, the SPP program will insert the
SL_PARSE macro for you there.

SL_PARSE takes four arguments.  The format is:

    SL_PARSE(argc, argv, on_prefix, off_prefix);
    int argc; char *argv[], *on_prefix, *off_prefix;

The first two arguments describe an argument list vector just like the argc
and argv arguments passed to main().  In other words, argv is a pointer to
a list of strings and argc is one more than the number of arguments in
argv[].  The argv vector is terminated by a NULL string so that  argv[argc]
is NULL.

The on_prefix and off_prefix arguments must be C strings, either string
literals or pointers to arrays of characters.  All arguments (i.e., all strings in
the argv vector) whose prefix is either on_prefix or off_prefix are
processed as Sherlock arguments and removed from the argv vector.  The
argc count is decremented by one for every deleted argument.  Arguments
that do not start with either the on_prefix or the off_prefix are not changed
by SL_PARSE.

Here is an example of a typical main routine:

    main(int argc, char ** argv)
    {
        declarations of local variables.

        SL_INIT();
        SL_PARSE(argc, argv, "++", "- -");

        executable statements...
    }

All examples in this manual will assume that the prefixes are ++ and - -.
However, any C string may be used for the off prefix or on prefix.  For
example, to set the on_prefix to !+ and the off_prefix to !-, you would use
the following call to SL_PARSE:

    SL_PARSE(argc, argv, "!+", "!-");

Here is a program that simply prints its command line arguments.  Note
that it will not print any Sherlock argument, i.e., any argument starting
with ++ or - -.

    /* Echo command line arguments. */
    main(argc, argv)
    int argc;
    char **argv;
    {
        int i;

        /* Process and remove Sherlock arguments. */
        SL_INIT();
        SL_PARSE(argc, argv, "++", "- -");

        /* Print non-Sherlock arguments. */
        argc- -;
        argv++;
        for (i = 1; i < argc; i++) {
            printf("argv[%d] = %s\n", i, *argv);
            argv++;
        }
    }

The SL_ON and SL_OFF macros also enable or disable tracepoints from
within your program and are easier to use than SL_PARSE.  Each macro
takes one argument, the name of the tracepoint to be enabled or disabled.
SL_ON enables the tracepoint while SL_OFF disables the tracepoint.  The
name of the tracepoint is not preceded by either the on_prefix or the
off_prefix.
The following example shows how to enable tracing for a selected range of
loop iterations:

    for (i = 0; i < 100; i++) {
        if (i = = 20) {
            SL_ON("complicated_function");
        }
        complicated_function(i);
        if (i = = 30) {
            SL_OFF("complicated_function");
        }
    }

The following sections discuss tracing macros, the heart of the Sherlock
system.


Tracepoint Names and Statistics: STAT, STATB and STATX

STAT is the simplest tracing macro.  It takes one argument, a tracepoint
name.  For example:

    STAT("rose");

Although closely related to the other tracing macros, STAT produces no
output.  STAT's only function is to provide a label for a count statistic,
which is simply the number of times control reaches the tracepoint defined
by STAT.  All tracing macros have a count statistic associated with their
tracepoint name.  Count statistics are always updated regardless of whether
tracing for a particular tracepoint has been enabled or not.

In order to provide better error checking, there are restrictions on the kinds
of characters that may appear in tracepoint names;  tracepoint names may
contain lower case letters, numerals and the underscore character, but not
blanks or special characters such as ( ) { } + etc.  The following are valid
tracepoint names:

    STAT("rose_is_a_rose");
    STAT("rose25");

The following are NOT valid tracepoint names:

    STAT("rose water");         blank character
    STAT("wine&roses");        & special character

There are two additional members of the STAT family, STATB and
STATX.  These two macros are used to gather timing statistics.  Timing
statistics are generally more useful than count statistics since they relate
directly to program speed.  On the other hand, timing statistics are a little
more difficult to gather than count statistics.  Timing statistics measure the
time spent in timing code.

The STATB macro works just like the STAT macro, except that the STATB
macro is an entry macro, that is, STATB defines the start of a section of
timing code.  Similarly, the STATX macro is an exit macro, that is, STATX
defines the end of a section of timing code.  In general, the suffix 'B' in the
name of a tracing macro indicates that the macro is an entry macro, while
the suffix 'X' in the name of a tracing macro indicates the macro is an exit
macro.  Count statistics are updated for STATB but not STATX.

Most often, timing code consists of an entire function, though that is not
required.  For example, to measure the time spent in a function without
generating any tracing message you would do something like:

int f()
{
    STATB("f");
    body of f;
    STATX("f");
}

The support routines keep track of statistics using an internal timing stack.
At run time, each entry macro must be paired eventually with an exit
macro.  For example, if you put an entry macro at the beginning of a
function then every exit from the macro must contain an exit macro.  When
an exit macro is executed, Sherlock verifies that its tracepoint name
matches the tracepoint name of the last entry macro, i.e., the macro on the
top of the timing stack.  A warning message occurs if there is a mismatch.
Such a warning indicates that timing statistics are not accurate.

The current nesting level is the number of entry macros that have been
executed for which an exit macro has not been executed.  The output from
all tracing macros is preceded by level dots, i.e., one period for each level
of nesting.

Sherlock provides two kinds of timing statistics: cumulative and non-
cumulative.  Cumulative timing statistics measure the total time spent in
timing code, including any time spent in nested timing code.  Non-
cumulative timing statistics excludes time spent in nested timing code.  In
other words, cumulative statistics are incremented at all levels of the timing
stack, while non-cumulative statistics are updated only at the top of the
timing stack.

The following paragraphs will be of interest only to advanced users of
Sherlock who wish to gather the best timing statistics possible.  Thanks go
to James E.G. Morris of Atari Games Corporation for suggesting
improvements in the way timing statistics are handled.

Version 1.5 of the support routines provides ways to adjust the timing
statistics gathered by Sherlock to factor out the overhead caused by calling
and returning from the Sherlock macros.  The Sherlock support routine
sl_dump() now  subtracts a "fudge factor," called TIME_ADJUST, from
the timing statistics as the report of the statistics is being generated.  This
fudge factor affects only the output of the SL_DUMP macroDthe actual
gathering of timing statistics is not affected in any way by
TIME_ADJUST.

The units of TIME_ADJUST are ticks per 1000 calls to Sherlock macros,
and TIME_ADJUST is supplied as a compile-time constant on the
command line when compiling sherlock.c.  If no value for
TIME_ADJUST is supplied, it is set to zero, which is what you get by
default.

The proper value of TIME_ADJUST depends on several factors: the speed
of your machine, its "tick" rate, the "speed up rate,"  i.e., the value of
sl_speed used in sherlock.c, which version of Sherlock macros is used,
preferred or alternate, and which memory model is used to compile your
program.  A new utility program, called measure.c, measures the time
overhead involved in calling Sherlock macros, and suggests appropriate
values for TIME_ADJUST.


Here I am Messages: TICK, TICKB, TICKN and TICKX

The simplest kind of tracing output is a "here I am" message.  The TICK
family of macros provide such messages.  The TICK macro takes exactly
one argument, a tracepoint name.  Examples:

    char name[] = "petunia";
    TICK(name);
    TICK("marigold");

If enabled, TICK simply prints the name of the tracepoint followed by a
colon.  The output created from the examples above would look like:

    petunia:
    marigold:

The only difference between TICK and TICKN is that TICK updates the
count statistic associated with the tracepoint name and TICKN does not.  In
general, the suffix 'N' in the name of a tracing macro indicates that count
statistics are not updated by the macro.

Why suppress the gathering of count statistics?   You might use TICKN
rather than TICK in order not to count the same section of code twice.  For
example:

    do {
        TICK("loop");
        ...
        TICKN("loop");
    } while (waiting);

Since only one TICK macro was used in the loop, the count statistic for
"loop" will reflect how many times the loop was executed.

As you would expect, the TICKB and TICKX macros are entry and exit
macros that otherwise work just like TICK.  Count statistics are updated
for TICKB but not TICKX.


Tracepoints Actions: TRACE, TRACEB, TRACEN and TRACEX

The TRACE family of tracing macros create code that lies dormant until the
appropriate tracepoint is enabled.

The members of the TRACE family take exactly two arguments.  As usual,
the first is a tracepoint name.  The second is a list of tracepoint actions,
consisting of one or more C language statements or blocks.  Statements in
the list of tracepoint actions are separated by semicolons as usual.  The list
may be terminated by a semicolon, but it doesn't have to be.   For example:

    TRACE("violet", printf("variable v = %d at xyz\n", v));

The tracepoint actions consist of a single print statement, namely:

    printf("variable v = %d at xyz\n", v);

The print statement will be executed only if the tracepoint named "violet"
has been enabled.

Any number of C statements may appear in the list of tracepoint actions.
For example:

    TRACE("peach",
        arg = xyz;
        p=f(arg);
        printf("f(xyz) is %lx at xyz\n", p));

The tracepoint actions consist of the three C statements:

    arg = xyz;
    p=f(arg);
    printf("f(xyz) is %lx at xyz\n", p);

Note that commas within an instruction in the list of tracepoint actions do
not change the number of arguments to TRACE.  You can write any C
statements in the list of tracepoint actions.  Make sure, though, that you get
enough parentheses at the end of the macro.  Without a trailing parenthesis,
the C preprocessor will complain about the actual parameters to the macro
being too long.

Statements in the list of tracepoint actions may even contain other macros.
For example:

    TRACE("abc",TRACE("xyz",
        printf("abc and xyz both enabled\n")));

The TRACEB, TRACEN and TRACEX macros function similarly to the
TRACE macroDthe TRACEN macro does not update count statistics,
while the TRACEB macro is an entry macro and the TRACEX macro is an
exit macro.


TRACEP, TRACEPB, TRACEPN and TRACEPX

The four members of the TRACEP family function just like the
corresponding four members of the TRACE family except that the
members of the TRACEP family print the name of the tracepoint, a colon
and a space before executing the tracepoint actions.  This is often just what
you want and it saves a little space in your program.  For example, the
following two macros are exactly equivalent, except that the TRACEP
macro takes less space:

    TRACE("daisy", printf("daisy: (arg: %d)\n", n));
    TRACEP("daisy", printf("(arg: %d\n", n));

In order to keep the names of the macros straight, it is useful to think of
TRACE and TRACEP as separate families of macros.  In other words, the
letter 'P' is  not  a suffix.  For example, there is a macro named TRACEPB
but no macro named TRACEBP.

The SPP program uses TRACEPB macros to trace the arguments on entry
to a function.  For example, SPP will insert a TRACEPB as shown:

    int example (char *s, int i, float f)
    {
        TRACEPB("example",
            printf("(%s, %d, %f)\n", s, i, f));
        ...
    }


Other Tracepoint Actions

All the tracepoint actions shown so far have consisted of printf statements.
While that is common, it is often useful to use other statements.  Sherlock
is an open ended tool;  the following paragraphs discuss various kinds of
statements that may be used inside macros.

fprintf statements: Useful for sending tracing output to someplace other
than the console.  Note that output generated from macros is sent to the
standard output stream so that if you redirect output using fprintf be sure to
redirect the standard output stream as well.  For example:

    TRACE("mum", fprintf(out_file, "mum: (%s)\n", flower_name));

Function calls: Useful for printing the contents of complicated data
structures.  This is an important benefitDyou can afford to create tracing
tools that produce a lot of output, because they will be called only when
needed.  You won't get swamped with unwanted output.

For example, suppose you have written a routine called print_vcs() which
prints the contents of a complicated data structure.  You would want to
control that routine by putting it in a Sherlock macro as follows:

    struct very_complicated_struct *vcsp;
    ...
    TRACE("vcs2", print_vcs(vcsp));

Assignment statements: Useful for controlling debugging switches using
command line arguments.  Use assignment statements with caution: they
may produce unexpected results if you enable all tracepoints with a
wildcard.  For example, suppose you have a variable called enable_pass2
which controls whether your program will call a routine called pass2().
You can disable that routine from the command line if you insert the
following into your program:

    TRACE("no_pass2", enable_pass2 = FALSE);

Flow of control statements: These may sometimes be useful for altering the
operation of your program while debugging.  Just as with assignment
statements, use these kinds of statements with caution.  For example, you
might want to set up a header for some kind of report as follows:

    TRACE("hdr", if(hdr= =NULL){hdr="Pre-Release Version";});

Other Sherlock macros: Sherlock macros may be nested.  This can be used
to create levels of debugging.  Indeed, it is often helpful to have several
tracepoints with the same name, e.g., v for verbose.  In the following
example, the function named dump() is called only if both the verbose
option and the dump_x option have been enabled.

    TRACEN("v", TRACE("dump_x", dump(x)));


The RETURN_xxx Family of Macros

There are eleven members of the RETURN_xxx family.  All are exit
macros.  In addition to signaling the end of timing code, these macros take
the place of return instructions.  There is one RETURN_xxx macro for
each type that a function can return: char, double, float, int, long, unsigned
int, unsigned long and void, and several additional macros for types that
benefit from special formatting: bool, pointer and string.

The RETURN family consists of the following members:
RETURN_BOOL, RETURN_CHAR, RETURN_DOUBLE,
RETURN_FLOAT, RETURN_INT, RETURN_LONG,
RETURN_UINT, RETURN_ULONG, RETURN_PTR,
RETURN_STRING and RETURN_VOID.

All RETURN_xxx macros except RETURN_VOID take two arguments,
the second of which is an expression of the type indicated by the macro.
The expression is evaluated exactly once, regardless of whether the
tracepoint is enabled.  If so, the macro prints out a message telling the
value of the expression.  For example:

    RETURN_BOOL("begonia", 0);


The last example prints the following message if begonia is enabled:

    begonia: returns: FALSE

Here are some more examples:

    RETURN_VOID("void_function");
    RETURN_BOOL("boolean", pi = = 3);
    RETURN_CHAR("character", '@');
    RETURN_DOUBLE("double_precision", (double) sin(x));
    RETURN_FLOAT("floating_point", sin(pi/2.0));
    RETURN_INT("integer", floor(i));
    RETURN_UINT("unsigned_int", 0xffff);
    RETURN_ULONG("unsigned_long", 0xffff);
    RETURN_LONG("long", 0L);
    RETURN_PTR("pointer", malloc(255));
    RETURN_STRING("string", p -> name);

SPP will replace all return instructions by RETURN_xxx macros.  For
example, the following instruction:

    return &array[25];

will be replaced by:

    RETURN_PTR(&array[25]);

SPP will generate RETURN_BOOL macros for all functions declared bool
as long as the following typedef appears before the function:

    typedef int bool;

Be aware that SPP treats all pointers to char as being pointers to a valid
string. This will cause problems in functions such as malloc() which return
a pointer to char which may not be used as a string.  Change
RETURN_STRING to RETURN_PTR in such cases.


Printing Statistics: SL_DUMP and SL_CLEAR

The SL_DUMP macro prints out a report of all statistics gathered so far.
It takes no arguments and can be called at any time.  For example:

    SL_DUMP();

The report contains several columns. The tracepoints column is an
alphabetized list of tracepoint names, the ticks column gives count statistics
for each tracepoint name, the times1 column gives non-cumulative timing
statistics, the times2 column gives cumulative timing statistics and the
tracing column indicates whether the tracepoint was enabled at the time
SL_DUMP was called.

The SL_CLEAR macro zeros all statistics.  Statistics are zeroed by
SL_INIT so you normally don't need to use SL_CLEAR.  It might be
useful, though, if your program were divided into phases and you wanted
to keep separate statistics for each phase.


Command Line Arguments

Any command line argument which starts either with the on_prefix or the
off_prefix is interpreted as a command to enable or disable a tracepoint or
group of tracepoints.  For example, suppose the program you are testing,
called z, is usually invoked with two arguments as follows:

    z in out

To enable the tracepoint called abc, precede its name with the on_prefix,
i.e., ++.  Like this:

    z ++abc in out

A Sherlock argument may appear anywhere on the command lineDits
position relative to non-Sherlock arguments does not matter because
SL_PARSE eliminates all Sherlock arguments from the argv vector.  As far
as the rest of your program is concerned, the command line is:

    z in out

Use the asterisk wildcard and question mark wildcard to select groups of
tracepoints.  The asterisk (*) matches zero or more characters and the
question mark (?) matches exactly one character.  For example, the
following enables all tracepoint names that start with "abc" :

    z ++abc* in out

The following enables all tracepoint names that start with abc and contain
exactly five letters:

    z ++abc?? in out

Any argument which starts with the off_prefix, i.e., '- -', disables one or
more tracepoints.  Sherlock evaluates arguments from left to right, so that
their order is significant.  The following enables all tracepoint names
starting with abc except abc1:

    z ++abc* - -abc1 in out

The following enables all tracepoint names starting with abc except those
containing exactly five characters, and in addition the tracepoint named
abc12 is also enabled:

    z ++abc* - -abc?? ++abc12 in out

It is easy to use wildcards to enable or disable groups of tracepoints if you
name your breakpoints in a systematic manner.  A good scheme is to prefix
all tracepoint names in a function with the name of that function.

The tracepoint name called "trace" is treated as a special case.  Disabling
that tracepoint name disables all tracepoints.  For example, the following
two command lines will produce identical results, but the first will execute
more quickly than the second:

    z - -trace in out
    z in out

Tracepoints can be re-enabled using the SL_PARSE or SL_ON macros,
but beware of putting those macros inside some other macro, such as
TRACE.  In other words, the following will not work if all tracing has
been disabled:

    TRACE("any", SL_ON("*"));

You can temporarily disable a tracepoint by preceding its name with a
disable count.  For example, the following will suppress the execution of
the first 100 calls to the tracepoint called loop_trace, after which it will be
enabled.

    z in out ++100loop_trace

You can temporarily disable all tracepoints (except STAT macros) by giving
a global disable count, which is simply the on_prefix followed by a count.
For example, the following will suppress all tracepoints until 1000 macros
have been encountered, after which only abc will be enabled:

    z ++1000 ++abc in out

Beware of extra spaces in command line arguments.  Compare the
following lines:

    ++99abc
    ++99  abc

The first command line has an argument containing a disable count for abc.
The second command line contains two arguments: a global disable count
and a second argument which is not a Sherlock argument at all.


Macro Definitions: Header Files and the SHERLOCK Constant

Sherlock's macros are defined in a header file called sl.h.  This header file
must be included in each source file that contains a macro.  A good way to
do this is to put the following line in a "master header file" which is
included in all source files of your program:

    #include "sl.h"

The expansion of macros is controlled by a compile time constant called
SHERLOCK.  Macros expand to code only if this variable is defined.  The
value of SHERLOCK is not important, only whether it has been defined or
not.  The constant SHERLOCK must be defined before the file sl.h is
included.  Thus, the following lines must appear in the order shown:

    #define SHERLOCK 1
    #include "sl.h"

To completely remove the effects of all Sherlock macros from a file,
without removing the macros themselves, you need only undefine the
constant SHERLOCK as follows:

    #undef SHERLOCK
    #include "sl.h"

If you want to disable a single Sherlock macro, just bracket it with #undef
SHERLOCK and #define SHERLOCK statements as follows:

    #undef SHERLOCK
    sherlock macro
    #define SHERLOCK 1

There may be times when you may want to bracket code with #ifdef
SHERLOCK and #endif.  For example, you might define two different
signon messages, depending on whether Sherlock macros are in effect:

    #ifdef SHERLOCK
    #define USAGE "usage: cb [++- -tracing routine] in [out]"
    #else
    #define USAGE "usage: cb in [out]"
    #endif

The file s11.h contains a set of alternate macro definitions.  Most compilers
will have no problems with the macros defined in sl.h.  However, some
compilers complain about duplicate definitions of a variable called h when
compiling the macros defined in sl.h.  If that happens, use the file sl1.h
instead of sl.hDthat will fix the problem.  Make sure, though, that you use
sl1.h only as a last resort.  The macros defined in sl1.h work much more
slowly than the preferred macro definitions in sl.h.



CHAPTER 4  DEBUGGING WITH SHERLOCK


This chapter offers tips on how to find and correct bugs more effectively.
Whether you are a student, a hobbyist or a professional programmer, you
would probably tackle any kind of programming task with confidence and
enthusiasm if you could be assured of finding all the bugs that might be
lurking in your code.   Debugging is a crucial step in the programming
processDit  separates working, successful programs from non-working
failures.  C programs are particularly challenging to debug because the C
language does not limit what you can do.  C does not attempt protect you
from your own mistakes.  The challenge of debugging C stems directly
from the flexibility and power which C provides.


Pointer Bugs

The key to learning how to debug C programs is recognizing,
understanding and correcting pointer bugs.  Pointers pervade all of C and
they give the C language much of its power and flexibility.  However,
pointers are dangerous, as well as useful.

This section addresses the most common situations involving pointer bugs:

o Pointer bugs arise from uninitialized pointers, dangling pointers and
incorrect use of arguments to function.

o Pointer bugs often destroy the computer code.  The code destroyed by
pointer bugs may have been the code you wrote, code comprising run-time
functions such as printf(), or operating system code.

o To the new C programmer, pointer bugs produce symptoms that look like
hardware malfunctions or compiler bugs.  The experienced C programmer
recognizes these same symptoms as clear indications of the existence of
pointer bugs.


Types of Pointer Bugs

Pointer bugs arise from uninitialized pointers, dangling pointers and
incorrect use of arguments to functions.  An uninitialized pointer is simply
a pointer variable which is used before it has been given a value.

For example,

    error1()
    {
        char *p;
        *p = 'a';
    }

In this example, p does not point to any specified location at the time that it
used to store the character 'a'.  The location in memory is not specified by
the code, and the results are unpredictable.  Possible symptoms will be
discussed later.

The second type of pointer bug is the dangling pointer.  A dangling pointer
refers to an area of memory which is no longer being used for its original
purpose.  For example,

    error2()
    {
        char *p, *malloc();
        p = malloc(25);
        free(p);
    }

The call to malloc() makes p point to an area of memory containing room
for 25 characters.  The call to free() deallocates the space and causes p to
become a dangling pointer. However, there is no bug in this code.  Any
time you deallocate memory you create a dangling pointerDbugs arise from
using dangling pointers rather than just creating them.

Again, the results of using a dangling pointer are unpredictable.  They are
not specified by the C program.  In this example, if the memory released by
the call to free() is later reallocated, using p will probably corrupt the newly
allocated memory.

A third kind of pointer bug is the mistaken parameter bug.  A good example
is the following:

    error3()
    {
        int i;
        scanf("%d", i);
    }

This will not work as expected.  The second argument to scanf() should
have been &i, not i.  The scanf() function expects a pointer to i and gets the
value of i instead.  Thus, the pointer that scanf() expects is incorrect.  Once
again this creates a hard-to-find bug.

This kind of error can corrupt the system stack.  This happens because the
called routines assume the stack has a different structure from the stack that
was actually created by the caller.  If the called program alters any stack
variable, it will be altering a part of the stack that may not actually
correspond to the location of the stack variable.

Note:  this kind of bug may largely be eliminated by using function
prototyping which will be part of the new ANSI C standard.


Effects of Pointer Bugs

Having looked at three kinds of pointer bugs, we see that their effects can
be devastating.  Any pointer bug has the potential for destroying any part of
memoryDexecutable code, library functions such as printf(), the system
stack used to keep track of procedure calls and returns or even the operating
system itself.  Exactly which part of memory depends on the value the
pointer had at the time your program was loaded.


Symptoms of Pointer Bugs

The symptoms of pointer bugs vary depending on just what kind of code or
data area are destroyed by the bug.  Such symptoms can not be taken at
face value. When confronted with behavior such as described below,
always think first of pointer bugs.


Symptom 1:
Your program crashes inside a function which you have
written and which you know to be debugged.

Cause:
A pointer bug has destroyed your carefully debugged function.

Symptom 2:
A library function suddenly ceases to work correctly.

Cause:
A pointer bug has destroyed the library function instead of your own code.

Symptom 3:
A bug is solid, i.e., it manifests itself in the same way when you run
the program several times.  However, the bug goes away when you insert print
statements into the code to get more information about it.

Cause:
Inserting the print statements changed the location of various parts
of your code.  Before the print statements were inserted, the pointer bug
destroyed code that was still to be executed.  After inserting the print
statements, the pointer bug destroyed a part of the program which was no
longer executed after the pointer bug occurred.

Symptom 4:
The symptoms of a bug change after you insert print statements.

Cause:
Inserting print statements changed the code destroyed by the pointer bug.

Symptom 5:
By inserting print statements you can determine that control reaches a
particular statement but not the statement immediately following.

Cause:
A pointer bug has destroyed one or both of the statements.

Symptom 6:
Your program calls a function, but control never reaches the function.

Cause:
A pointer bug has destroyed either the system stack or the function itself.

Symptom 7:
Control never returns to the caller of a function after the called function
returns.

Cause:
A pointer bug has destroyed either the run-time stack or the function itself.

Symptom 8:
Your program sometimes works and sometimes crashes.

Cause:
An uninitialized variable is destroying random parts of your program depending
on the contents of certain memory locations before your program was invoked.
The pointer bug is destroying different memory locations each time your program
is being run.  Sometimes the destroyed locations do not affect your program and
sometimes they do.

Symptom 9:
Your program always works once, but fails the second time it is run.

Cause:
Your program contains an uninitialized variable.  The first time your
program runs the variable is initialized in a uniform way which does not
cause any apparent harm.  The second time your program runs, the variable
has a new initial value which depends on the program's first run.  This
second initial value causes the symptoms the second time the program is
run.


Using Sherlock to Find Bugs

Using Sherlock to locate bugs is a two-step process.  The process requires
that the bug happen consistently and that you make a plausible guess about
its cause.


Step 1:  Stabilize the Symptoms.

The first step in finding the cause of any bug is to make the bug "stand
still" so that you can study it.  You can do this in the following ways:

1. Fill memory with a constant value before you run your program.  This
will insure that uninitialized pointers get the same (though probably still
incorrect) value from run to run.  If filling memory with a constant value
makes the symptoms of your bug go away, you can be reasonably sure that
some kind of initialization problem is causing the bug.

2. Eliminate the effects (including symptoms) of most dangling pointers by
disabling any routine which frees a dynamically allocated data structure.
You can do that by providing an alternative deallocation routine which is a
dummy routine. When you do that, dangling pointers no longer dangle,
i.e., they no longer point to deallocated memory.  If disabling a routine
such as free() makes the symptoms of your bug go away, you can be
reasonably sure that a dangling pointer is at hand.

3. Keep precise records about how you invoked your program.  An easy
way to do this is by invoking the program from a batch file, also known as
a submit file or shell file. That way the batch file serves as a record for
exactly what you have done.  A tip:  when you change the arguments to
your program, comment out the old line and save it in the batch file as a
record of the your previous runs.  This is especially handy when using
numerous Sherlock tracepoints to change the behavior of your program
during testing.

4. Keep your program unchanged.  Since pointer bugs destroy code, even
the smallest change in your program, or even a change in the order in
which functions are linked together, may cause the symptoms of pointer
bugs to change or even go away.  Sherlock is a huge help here.  Enabling
or disabling different tracepoints does not change the location of any code
in your program.  You can run test after test on your program, getting very
different information each time, and the symptoms of pointer bugs will not
change.


Step 2:  Make a Reasonable Guess about the Cause.

The next step in finding a bug is to make a guess about what is causing it.
If any of the symptoms mentioned above appear, you probably should
assume that a pointer bug is causing your problems.  Use Sherlock to look
for bad pointers by tracing the parameters passed to all your functions.

If a supposed pointer has a small negative number as its value (.e.g.,
FFFFE hex), you can be sure that the pointer has already been corrupted.
You may also notice that a pointer does not have a reasonable value in some
other way.  Now ask yourself, "Which routines could have passed that
pointer on to the called routine?"  Rerun your program with different
tracepoints enabled which will trace the likely culprits.  Once you find the
source of a bad pointer, ask whether the code which created the bad pointer
was ultimately at fault or whether some other error resulted in the bad
pointer as a by-product.

Again, Sherlock stands out in being able to try numerous tracing runs on a
program without having to change the program in any way.  You will find
that patterns jump out at you as you look at traces and dumps produced by
Sherlock.  When you get a hint of something in a trace being "not quite
right," you can immediately start a new trace to zero in on those parts of the
program that are related to what caught your attention.  By varying your
traces to home in on suspects, you are eliminating vast amounts of
extraneous information in the debugging output.



CHAPTER 5  SHERLOCK REFERENCE


This chapter provides reference information about all aspects of the
Sherlock systemDit contains the most detailed and complete information
on any particular topic.  The first sections discuss the following subjects:
Header Files, Command Line Arguments, Entry and Exit Macros and the
Timing Stack, The Interrupt Handler, Compiling Support Routines,
Tracepoint Names and Tracepoint Actions.  The conclusion of this chapter
discusses each macro, symbol and support routine in alphabetical order.


Header Files

There are two sets of definitions of the Sherlock macros, the preferred
definitions in sl.h and the alternate definitions in sl1.h.The support routines
called by the alternate macros search an internal symbol table for their
tracepoint name every time they are called.  The preferred macros define a
static variable named h which is used to avoid searching the symbol table
after an initial search.  As a consequence, preferred macros are much faster
than the alternate macros.

Alas, some compilers do not allow multiple static variables with the same
name, even if the variables are declared in different blocks.  Use the
preferred macro definitions unless your compiler objects to constructions
such as:

    void test()
    {
        {static char *h = 0;}
        {static char *h = 0;}
    }


Command Line Arguments

A Sherlock argument is any command line argument whose prefix is either
the on_prefix or the off_prefix.  These prefixes are defined by the
SL_PARSE macro.  For example:

    SL_PARSE(argc, argv, "++", "- -");

All examples in this manual assume that the on_prefix is "++" and the
off_prefix is "- -", but any string of any length may be used for either
prefix.

The SL_PARSE macro processes all Sherlock arguments, deleting them
from the argv vector and adjusting the argc count appropriately.  Thus, any
code following the SL_PARSE macro will be completely unaware of the
existence of Sherlock arguments.

Two wildcard characters allow Sherlock arguments to specify classes of
tracepoints.  The asterisk (*) character matches zero or more characters.
For example, the argument

    ++abc*

enables tracing for any tracepoint whose name begins with abc. The
asterisk, if present, should be the last character of a Sherlock argument.

The question mark (?) character matches exactly one character.  For
example, the argument

    - -abc??

disables tracing for abc12 and abc34 but not abc1 or abc123.

Sherlock arguments are processed left to right.  The order is significant.
For example, the following (partial) command line turns on tracing for
abc1

    - -abc* ++abc1

As another example, the effect of the first argument in the command line
below will always be immediately canceled by the second argument.

    ++abc? - -abc*

If the on_prefix or off_prefix is immediately followed by a number, that
number is taken to be a disable count.  If a name follows the disable count,
tracing for that tracepoint is disabled until that tracepoint has been executed
n times, where n is the disable count.  For example,

    ++100abc

disables tracing for the tracepoint named abc until abc has been reached 100
times.

If no string appears after the disable count, it is a global disable count
which applies to all tracepoints.  All tracing is disabled until n tracepoints
have been encountered.  For example:

    ++1000

disables all tracing until 1000 tracepoints have been executed.


Entry and Exit Macros and the Timing Stack

Timing statistics measure the time spent in timing code delimited by two
special kinds of macros.  Entry macros signal the beginning of timing
code, while exit macros signal the end of timing code.  The support
routines use an internal timing stack to gather timing statistics in nested
sections of timing code.

There are two kinds of timing statistics: cumulative and non-cumulative.
Cumulative statistics measure the total time spent in timing code, including
any time spent in nested timing code.  Non-cumulative statistics excludes
time spent in nested timing code.

At run time, each entry macro requires a corresponding exit macro.  If an
exit macro is omitted, a timing stack overflow will eventually result.  If an
extra exit macro is encountered, a timing stack underflow may follow.  A
timing stack overflow or underflow indicates that the timing statistics
gathered are not accurate.  Sherlock prints a warning message and a stack
traceback when either an overflow or an underflow is detected.  The global
variable, sl_level, indicates the current nesting depth of timing macrosDit
is incremented by entry macros and decremented by exit macros.  You can
use the sl_level variable to track down timing stack overflows or
underflows.


The Interrupt Handler

An interrupt handler is used to gather timing statistics.  In concept, the
purpose of the handler is simple: to increment the global C variable called
sl_count each time a timing interrupt occurs.  However, the code for the
interrupt handler is tricky.

Warning: The interrupt handler is inherently machine dependent.  It will
work only on machines which are 100% compatible with the IBM PC, XT
or AT.  It will be necessary to rewrite the interrupt handler if you want to
gather timing statistics on other machines.

The interrupt handler consists of three parts: an initializer, a tick handler
and an exit handler.  The initializer changes the hardware interrupt trap
vectors to point to entry points inside the tick handler and the exit handler.
The initializer also increases the frequency of the hardware timer interrupt.
It does this by directly writing to one of the timer chips.  The speed up
factor is determined by the value of the global C variable called sl_speed,
which is defined in the file sherlock.c.  The default speed-up factor is 55,
which gives an interrupt rate of about 1 interrupt per millisecond, assuming
a basic tick frequency of 18.2 ticks per second.


The tick handler receives control as the result of tick interrupts.  It
increments the global C variable called SL_COUNT.  It also passes on
selected ticks on to the default tick handler so that the nominal tick
frequency of 18.2 ticks per second is maintained.

The exit handler gets control from any DOS function call or interrupt that
results in an exit from the program.  This exit handler restores all the
interrupt vectors which were changed by the initializer.


Compiling Support Routines

The source code for the support routines was developed on the Turbo C
compiler version 1.5 and will compile correctly with the Microsoft C
compiler version 5.0 or later.

The source code for the support routines uses function prototypes which
are a part of the draft ANSI C standard.  Not all current compilers support
function prototypes.  To compile
Sherlock on compilers that do not, comment out the definition of the
compile time variable called HAS_PROTOTYPES at the start of the header
file sl.h.


Tracepoint Names

Tracepoint names are strings which must contain only the following
characters: the letters a-z and A-Z, the numbers 0-9 and the underscore
character.  A warning message is printed if a macro is passed a tracepoint
name which contains any other character.


Tracepoint Actions

Tracepoint actions consist of a statement list consisting of zero, one or
more C language statements.  Statements must be separated by semicolons
as usual.  The statement list may be terminated by a semicolon, but need
not be.


Macros, Global Variables and Support Routines

The following sections discuss each Sherlock macro and variable and a few
globally visible support routines.  All entries appear in alphabetical order.


Macros:
    RETURN_BOOL  (tracepoint_name, boolean_expression)
    RETURN_CHAR  (tracepoint_name, char_expression)
    RETURN_DOUBLE(tracepoint_name, double_expression)
    RETURN_FLOAT (tracepoint_name, float_expression)
    RETURN_INT   (tracepoint_name, int_expression)
    RETURN_LONG  (tracepoint_name, long_expression)
    RETURN_PTR   (tracepoint_name, pointer_expression)
    RETURN_STRING(tracepoint_name, string_expression)
    RETURN_UINT  (tracepoint_name, unsigned_int_expression)
    RETURN_ULONG (tracepoint_name, unsigned_long_expression)
    RETURN_VOID  (tracepoint_name)

Synopsis:    Print tracepoint name.  Print and return the value of the
expression.

Examples:
    RETURN_BOOL  ("abc", a ? 0 : 1);
    RETURN_CHAR  ("abc", "\n");
    RETURN_DOUBLE("abc", 0.6666666666666666);
    RETURN_FLOAT ("abc", 3.14159);
    RETURN_INT   ("abc", a - 15);
    RETURN_LONG  ("abc", 1L);
    RETURN_PTR   ("abc", &abc);
    RETURN_STRING("abc", "this is a test");
    RETURN_UINT  ("abc", (unsigned) 0xffff);
    RETURN_ULONG ("abc", (unsigned) 0xffff0000);
    RETURN_VOID  ("abc");

These macros are all exit macros.  Each macro prints the tracepoint name, a
colon, a space, "returns", a colon, a space, followed by the value of the
expression.  The RETURN_VOID macro prints "void" in place of the
value of the expression.  Each macro completes and records the timing
statistics associated with the timing section begun by the corresponding
entry macro.  Each macro then returns from a function of the indicated
type.

At run time, each of these macros must be matched with an entry macro.  If
an exit macro is encountered without a corresponding entry macro, a timing
stack underflow will eventually occur.

The SPP utility program will generate RETURN_BOOL macros for all
functions declared bool as long as the following typedef appears before the
function:

    typedef int bool;

Be aware that SPP treats all pointers to char as being pointers to a valid
string. This will cause problems in functions such as malloc() which return
a pointer to char which may not be used as a string.  Change
RETURN_STRING to RETURN_PTR in such cases.


Compile time symbol:    SHERLOCK

Synopsis:    Enable or disable expansion of all Sherlock macros.

Example:    #define SHERLOCK 1
        #include "sl.h"

Sherlock's macros expand into actual code only if this symbol is defined.
The value assigned to the variable SHERLOCK does not matter, only
whether it is defined or not.  If SHERLOCK is not defined, then all
Sherlock's macros expand to no code, or a return statement in the case of
RETURN_xxx macros.

Notice that the definition of SHERLOCK must precede the definitions of
the macros in sl.h.  The following will not work as expected:

    #include "sl.h"
    #define SHERLOCK 1

Do this instead:

    #define SHERLOCK 1
    #include "sl.h"

Actually, it is usually a good idea to enable the SHERLOCK constant from
the command line.  When using the Microsoft C compiler, use the /D
option, like this:

    /DSHERLOCK

When using the Turbo C compiler, use the -D option, as follows:

    -DSHERLOCK


Support Routines:
    typedef int bool;
    void    sl_bout(bool b);
    void    sl_cout(char c);
    void    sl_dout(double d);
    void    sl_iout(int i);
    void    sl_lout(long l);
    void    sl_pout(void * s);
    void    sl_sout(char * p);
    void    sl_uiout(unsigned int ui);
    void    sl_ulout(unsigned long ul);

Synopsis:
    sl_bout:    Print a boolean expression using sl_cout().
    sl_cout:    Print a character using putchar().
    sl_dout:    Print a double or float expression using sl_cout().
    sl_iout:        Print an int expression using sl_cout().
    sl_lout:        Print a long expression using sl_cout().
    sl_pout:    Print a pointer expression using sl_cout().
    sl_sout:    Print a string using sl_cout().
    sl_uiout:    Print an unsigned int expression using sl_cout().
    sl_ulout:    Print an unsigned long expression using sl_cout().

Example:
    void sample(b, c, d, f, i, l, p, s, u, ul)
    bool b; char c;
    double d; float f;
    int i; long l;
    struct some_struct *p; char *s;
    unsigned ui; unsigned long ul;
    {
        TICKB("sample",
            sl_bout(b); sl_sout(", ");
            sl_cout(c); sl_sout(", ");
            sl_dout(d); sl_sout(", ");
            sl_dout(f); sl_sout(", ");
            sl_iout(i); sl_sout(", ");
            sl_lout(l); sl_sout(", ");
            sl_pout(p); sl_sout(", ");
            sl_sout(s); sl_sout(", ");
            sl_uiout(u); sl_sout(", ");
            sl_ulout(ul));
        ...
        TICKX("sample");
    }

These support routines print a single expression of the indicated type.  The
sprintf() function is used to format the value into a character buffer, which
is then printed using sl_sout().  The sl_sout() routine calls sl_cout() so the
output of all these routines eventually is funneled through sl_cout().
Indeed, all output produced by the macros and the support routines
eventually is handled by sl_cout().


Macro:        SL_CLEAR()

Synopsis:    Clear all statistics.

Example:    SL_CLEAR();

See also:    SL_DUMP

This macro clears all the statistics gathered so far.  The SL_INIT macro
also does this, so normally there is no need to use this macro.  You might
use this macro to begin gathering statistics about a selected portion of your
code.  Call SL_CLEAR at the start of the section and SL_DUMP at the end
of the section.


Macro:        SL_DUMP()

Synopsis:    Write a report of statistics.

Example:    TRACE("dump", SL_DUMP());

See Also:    SL_CLEAR

This macro writes a report of all the statistics gathered for all tracepoints
encountered so far.  Output is written using the sl_cout() support routine.

The report contains five columns. The tracepoints column is an
alphabetized list of tracepoint names.  The ticks column gives count
statistics for each tracepoint name.  The times1 column gives non-
cumulative timing statistics and the times2 column gives cumulative timing
statistics.  The tracing column indicates whether the tracepoint was enabled
when SL_DUMP was called.

Reports may be enabled from the command line by inserting the
SL_DUMP macro in another macro such as TRACE or TRACEN.


Macro:        SL_INIT()

Synopsis:    Initialize Sherlock's support routines.

Example:
    main(argc, argv)
    int argc;
    char **argv;
    {
        /* Local declarations. */
        SL_INIT();
        SL_PARSE(argc, arg, "++", "- -");

        /* Sherlock arguments not visible here. */
        ...
    }

This macro initializes Sherlock's support routines.  It must be called before
any other Sherlock macro.


Global Variable:
    sl_level

Synopsis:
    The current nesting level.

Example:
    if (sl_level > 0) {
            printf("unmatched entry macro.\n");
    }

This global variable is incremented every time an entry macro is
encountered and is decremented every time an exit macro is encountered.
This variable can be used to find unpaired entry and exit macros.


Macro:        SL_NAME(tracepoint_tag, tracepoint_name)

Synopsis:    Define a static char array which can be used as a tracepoint
        name.

Example:

    int
    long_winded_function_name()
    {
        SL_NAME(func2_tag, "long_winded_function_name");
        TICKB(func2_tag);
        ...
        RETURN_VOID(func2_tag);
    }

Use the SL_NAME macro to reduce the space required to store tracepoint
names.  In the example above, space for the string "func2" is allocated
once, rather than twice.

Note: The SDEL program will retain all SL_NAME macros if the -r option
is given to SDEL.  Use the -r option when using SDEL to delete Sherlock
macros just prior to reinserting them with SPP.


Macros:
    SL_OFF(tracepoint_name)
    SL_ON(tracepoint_name)

Synopsis:
    SL_OFF:    Disable one or more tracepoints.
    SL_ON:    Enable one or more tracepoints.

Examples:
    SL_OFF("abc");
    SL_ON("200abc");

Special cases:
    SL_OFF("trace");
    SL_ON("trace");

See Also:        SL_PARSE

These macros enable or disable the tracing for a single tracepoint, just as if
the name of the tracepoint were appended to the end of the command line.
Neither the on_prefix nor the off_prefix is used.  Wildcard characters and
disable counts are allowed.  The name "trace" is a special case which
enables or disables the tracing of all tracepoints.


Macro:
    SL_PARSE(argc, argv, on_prefix, off_prefix)

Synopsis:
    Enable or disable tracepoints indicated by an argument vector.

Example:
    SL_INIT();
    SL_PARSE(argc, argv, "++", "- -");

See also:    SL_ON, SL_OFF

This macro enables or disables tracepoints indicated by an argument vector
and removes all Sherlock arguments from the vector.

The argc argument gives a count of the number of elements in the argv
argument, which is an array of pointers to strings.  The on_prefix and
off_prefix arguments are strings which denote Sherlock command line
arguments.  Arguments in argv starting with on_prefix enable tracing,
while arguments in argv starting with off_prefix disable tracing.

The argv vector is scanned for argc - 1 arguments starting with argv[1].
Argv[0] is ignored.  When arguments starting with either the on_prefix or
off_prefix are found, the indicated tracepoint is enabled or disabled, the
argument is removed from the argv vector and the argc count is
decremented.  On entry to SL_PARSE, argv[argc] must be NULL.

This macro may be called more than once and the argc and argv arguments
need not be the same as the argc and argv arguments passed to the main()
function by the operating system.  In other words, you are free to call this
macro with a "simulated command line."  For example:

    static int count = 4;
    static char * vect [] =
        {NULL, "++*", "- -sys*", "++sys_fopen", NULL};

    ...

    SL_PARSE(count, vect, "++", "- -");


Support Routine:
    sl_regs()

Synopsis:
    Put the contents of all machine registers into global variables.

Example:
    TRACE("dump_regs", sl_regs());

This support routine does not have a corresponding macro.  It places the
contents of the PC's registers into global memory locations.  See regs.asm
for details.


Macros:
    STAT(tracepoint_name)
    STATB(tracepoint_name)
    STATX(tracepoint_name)

Synopsis:
    STAT:    Update the count statistics for a tracepoint.
    STATB:    Entry macro.  Otherwise same as STAT.
    STATX:    Exit macro.  Otherwise same as STAT.

Example:
    int f1()
    {
        int i, val;
        STATB("f1");
        for (i = 0; i < 5; i++) {
            STAT("f1_loop");
            val++;
        }
        STATX("f1");
    }

These STAT family of macros update the count statistics associated with the
tracepoint name, regardless of whether the tracepoint name is enabled or
not.  This family of macros never produces output.  The STATB macro
begins timing code and the STATX macro ends timing code.


Macros:
    TICK(tracepoint_name)
    TICKB(tracepoint_name)
    TICKN(tracepoint_name)
    TICKX(tracepoint_name)

Synopsis:
    TICK:    Print the tracepoint name, a colon and a newline and update
        count statistic.
    TICKB:    Entry macro.  Otherwise same as TICK.
    TICKN:    Do not update count statistic.  Otherwise same as TICK.
    TICKX:    Exit macro.  Otherwise same as TICK.

Example:
    int f2(int i)
    {
        int val;

        TICKB("f2");
        for (i = 0; i < 5; i++) {
            TICK("f2_before");
            val++;
        }
        TICKX("f2");

        return val+5;
    }

If enabled, the TICK family of macros print the tracepoint name, a colon
and a newline using the sl_sout() support routine.

The TICK, TICKB and TICKX macros update the count statistics
associated with the tracepoint, whether enabled or disabled.  However, the
statistics are not updated if all tracing has been disabled as the result of
disabling the special tracepoint named "trace". The TICKN macro never
updates any statistics.

The TICKB macro begins timing code and the TICKX macro ends timing
code.


Macros:
    TRACE(tracepoint_name, code_list)
    TRACEB(tracepoint_name, code_list)
    TRACEN(tracepoint_name, code_list)
    TRACEX(tracepoint_name, code_list)

Synopsis:
    TRACE:     Execute code list and update count statistics.
    TRACEB:    Entry macro.  Otherwise same as TRACE.
    TRACEN:    Do not update count statistics.  Otherwise same as TRACE.
    TRACEX:    Exit macro.  Otherwise same as TRACE.

Example:
    int f3(int i)
    {
        int val;

        TRACEB("f3", printf("f3 entry: %d\n", i));
        for (i = 0; i < 5; i++) {
            TRACE("f3_loop",
                printf("f3: i = %d\n", i));
            val++;
        }
        RETURN_INT("f3", val+5);
    }

If enabled, the TRACE family of macros execute a code list containing
zero, one, or more executable C statements of any kind.

The TRACE, TRACEB and TRACEX macros update the count statistics
associated with the tracepoint, whether enabled or disabled.  However, the
statistics are not updated if all tracing has been disabled as the result of
disabling the special tracepoint named "trace".  The TRACEN macro never
updates any statistics.

The TRACEB macro begins timing code and the TRACEX macro ends
timing code.


Macros:
    TRACEP(tracepoint_name, code_list)
    TRACEPB(tracepoint_name, code_list)
    TRACEPN(tracepoint_name, code_list)
    TRACEPX(tracepoint_name, code_list)

Synopsis:
    TRACEP:     Print the tracepoint name, execute code list and
            update count statistics.
    TRACEPB:    Entry macro.  Otherwise same as TRACEP.
    TRACEPN:    Do not update count statistics.  Otherwise same as
            TRACEP.
    TRACEPX:    Exit macro.  Otherwise same as TRACEP.

Example:
    int f4(int i)
    {
        int val;

        TRACEPB("f4", printf("(%d)\n", i));
        for (i = 0; i < 5; i++) {
            TRACEP("f4_loop", printf("i = %d\n", i));
            val++;
        }
        RETURN_INT("f4", val+5);
    }

If enabled, the TRACEP family of macros print the tracepoint name, a
colon and a blank, and then execute a code list containing zero, one, or
more executable C statements of any kind.  The tracepoint name, colon and
blank are printed using the sl_sout() support routine.

The TRACEP, TRACEPB and TRACEPX macros update the count
statistics associated with the tracepoint, whether enabled or disabled.
However, the statistics are not updated if all tracing has been disabled as
the result of disabling the special tracepoint named "trace".  The
TRACEPN macro never updates any statistics.

The TRACEPB macro begins timing code and the TRACEPX macro ends
timing code.



CHAPTER 6  SPP REFERENCE

SPP is a utility program that copies an input file to an output file, inserting
Sherlock macros that trace the entry and exit of all functions.  TICKB
macros or TRACEPB macros containing printf statements are inserted at
the start of functions, return instructions are replaced by RETURN_xxx
macros, and TICKX macros are inserted where control might "fall off the
end" of functions.  SPP also inserts SL_INIT and SL_PARSE macros at
the start of the main() function.  Several command line options vary the
kind and quantity of macros output inserted by SPP.

SPP is essentially a source-to-source C compiler which understands the
type of all variables and functions.  SPP handles all styles of C syntax,
from K&R to the ANSI draft standard of January 11, 1988.  SPP is
robust: it flags all syntax errors and will place correct macros in the
appropriate locations in spite of most syntax errors.  It is recommended,
however, that  SPP be used only on files that contain no syntax errors,
i.e., on files that have been previously been compiled without generating
any error messages.

SPP generates RETURN_BOOL macros in functions declared bool as long
as the declaration:

    typedef int bool;

appears before the bool function.  SPP generates printf statements that
print boolean arguments as either "TRUE" or "FALSE" instead of 1 or 0.
This is done using calls to a support routine called sl_sbout().  The
RETURN_BOOL macro is not affected by this feature.For example, SPP
will insert the following macros:

    bool f(bool b)
    {
        TRACEPB("f", printf("(%s)\n", sl_sbout(b)));
        ...
        RETURN_BOOL("f", 1);
    }

SPP assumes that all pointers to characters are pointers to a valid string.
As a result, you should change the RETURN_STRING macros generated
by SPP to RETURN_PTR macros in functions such as malloc() which
return a pointer that can not be printed as a string.

SPP warns about functions that do not return a value and are not explicitly
declared void.

SPP issues the warning, "Macro found where entry macro should be," if
SPP finds a macro call where the first executable statement of a function is
expected.  In such cases, SPP will skip the generation of an entry macro,
i.e., TICKB or TRACEPB.  Instead, SPP assumes the macro starts
executable code.

For example:

    int f(void)
    {
        int a;
        MY_TRACE_MACRO(a);
        return a;
    }

SPP will generate the following code:

int f(void)
    {
        int a;
        MY_TRACE_MACRO(a);
        RETURN_INT("f",a);
    }

SPP generates macros for a function only if the first executable statement
of that function is not already a Sherlock macro.  SPP will generate the
warning, "Sherlock macros generated for this function," if a Sherlock
macro is encountered while generating macros for a function.  That is, the
warning will be generated if the function contains Sherlock macros but the
first executable statement is not a Sherlock macro.  This new feature is
very handyDyou can now run your source files through SPP any time you
add any function and SPP will leave the functions already containing
Sherlock macros alone.

Two new macros, SL_ENABLE() and SL_DISABLE(), allow function-
by-function control over SPP.  Both macros always expand to empty code.
Insert SL_DISABLE() as the first executable statement of a function in
which you want no more Sherlock macros to be inserted.  For example:

    int f(void)
    {
        declarations;
        SL_DISABLE();
        No Sherlock macros will be generated in this function.
    }

The SL_ENABLE() macro forces SPP to insert macros into a function.
Use this macro when a function starts with a Sherlock macro that you
inserted yourself.  For example:

    int do_command_line(int argc, char **argv)
    {
        declarations;
        SL_ENABLE();
        TRACEP("do_command_line",
                for (i = 1; i < argc; i++) {
                    printf("argv[%d]: %s\n", argc, argv);
                }
        );
        Sherlock macros will be generated as usual.
    }

Be sure to delete the SL_ENABLE() macro after SPP processes the
function.


Invoke SPP as follows:

    SPP input_file  output_file  [options]

SPP supports the INCLUDE environment variable, which is set with the
DOS set command.  For example, the DOS command:

    set INCLUDE=c:\include;d:\sherlock

will cause SPP to search the c:\include and d:\sherlock directories for
#include files.  The directories specified by the INCLUDE environment
variable are searched after any directories specified by the -s SPP option.

Options are one of the following:


-d <id>=<string>

Define <id> to be <string>, as if the statement #define <id> <string>
appeared at the start of the program.  A space must separate -d and <id>,
but no space may appear in <string> or around the equal sign.  The
<string> is optional, in which case the equal sign can be omitted.
Examples:

    -d STDC=1
    -d SHERLOCK


-f <file name>

Use alternate macro names.  The file named in <file name>  contains a list
of synonym lines.  Each line contains two macro names, a standard name
and a synonym.  SPP will output the synonyms instead of the standard
macro names.  The pound character (#) starts a comment which continues
to the end of the line.  An example synonym file:

    #synonym file:  May 20, 1988
    #
    TICKB        BEGIN_TIMING_CODE
    TICKX        END_TIMING_CODE
    SL_DUMP        REPORT_STATISTICS


-i

Insert the line #include <sl.h> at the start of the output file.


-n

Allow nested comments.  By default, comments do not nest.


-o
Output sl_cout() and related support routines instead of printf().  SPP
generates more compact code when using the -o option by generating calls
to three new support routines: sl_lpout(void), sl_rpout(void) and
sl_csout(void).  These routines are equivalent to sl_cout("("), sl_sout(")"),
and sl_sout(", ") respectively.


-s <path>

Add <path> to the list of paths used to search for include files.  More than
one -s option may be used.  A space must separate -s and <path>.  Example:

    -s \usr\include  -s \sources  -s \sherlock

-t

Suppress the generation of entry or exit macros.  TICK and TRACEP macros are
generated instead of TICKB and TRACEPB macros.  No RETURN_xxx macros are
generated.


-u <id>

Undefine <id>, as if the statement #undef <id> appeared at the start of the
program.  A space must separate -u and <id>.

-x

Do not recognize single-line comments.

By default, SPP recognizes single-line comments, which start with // and
continue to the end of the line.  As you would expect, the // sequence is
treated as ordinary characters in comments and inside strings.  Single-line
comments are not part of the Draft ANSI C standard, but are offered as
language extensions by several C compilers, including the Microsoft C
compiler.

A fine point:  each single-line comment is converted to a single blank in the
replacement text of a #define preprocessor directive.  The // characters and
any following characters do not become part of the replacement text of the
macro being defined.  This is consistent with how ordinary C comments
are handled in the Draft ANSI C Standard, and is also consistent with how
current C++ compilers work.  However, old C++ translators handled //
differently.  Warning: the description of single-line comments on page 130
of The C++ Programming Language, by Bjarne Stroustrup, describes the
anachronistic operation of the old C++ translators, not current C and C++
compilers.


Example:

Original program:

int example(char * string, double)
{
    int i;
    i = 25;
    return i;
}

Default output from SPP:

int example(char * string, double d)
{
    int i;
    TRACEPB("example",printf("(%s, %f)\n", string, d));
    i = 25;
    RETURN_INT("example", i);
}

Output from SPP with the -t option on:

int example(char * string, double d)
{
    int i;
    TRACEP("example",printf("(%s, %f)\n", string, d));
    i = 25;
    return i;
}

Output from SPP with the -o option on:

int example(char * string, double d)
{
    int i;
    TRACEPB("example",      sl_lpout();
        sl_sout(string);  sl_csout();
        sl_dout(d);       sl_rlout());
    i = 25;
    RETURN_INT("example", i);
}



CHAPTER 7  SDEL REFERENCE


SDEL is a utility program that copies an input file to an output file, deleting
all calls to Sherlock macros as it does so.  It is not usually necessary to
remove Sherlock macros from a program in order to eliminate all the code
generated by Sherlock macros.  Indeed, you can eliminate all Sherlock
tracing code from your application simply by undefining the constant called
SHERLOCK and recompiling your program.  However, there may be
times when you want to remove all Sherlock macros from one of your
source files.  For instance, you may want to delete all Sherlock macros
before automatically re-introducing them with SPP.

Invoke SDEL as follows:

    SDEL input_file output_file [options]

For your protection, the name of the input file may not be the same as the
output file, and the output file must not already exist.

Options are one of the following:


-d

Do not delete SL_DISABLE() macros.



-f    <file name>

Use alternate macro names.  The file named in <file name>  contains a list
of synonym lines.  Each line contains two macro names, a standard name
and a synonym.  SDEL will delete the synonyms instead of the standard
macro names.  The pound character (#) starts a comment which continues
to the end of the line.  An example synonym file:

    #synonym file:  May 20, 1988
    #
    TICKB        BEGIN_TIMING_CODE
    TICKX        END_TIMING_CODE
    SL_DUMP    REPORT_STATISTICS


-i

Remove any lines consisting solely of:

    #include "sl.h"


-n

Allow nested comments.  By default, comments do not nest.


-r

Retain all SL_NAME macros (or synonyms for SL_NAME) in the output.


-t

Output trigraph sequences instead of the following nine characters:

      #  [  ]  \  {  }  ^  |  ~



CHAPTER 8  SDIF REFERENCE


SDIF is a special purpose file comparison programDit compares two files
which should be identical except for the presence of Sherlock macros.
SDIF allows you to see at a glance which macros where inserted into a file
by SPP.  You can also use SDIF to check the operation of SPP and SDEL.
Given any file f.c containing Sherlock macros, the following sequence of
commands should produce output from SDIF consisting of lines containing
only white space:

    sdel f.c     temp1.c
    spp  temp1.c temp2.c
    sdel temp2.c temp3.c
    sdif temp1.c temp3.c

Invoke SDIF as follows:

    SDIF file1(with_macros)  file2(without_macros) [-b] [-v]

File1 is assumed to be identical to file2 except that file1 contains Sherlock
macros and file2 does not.

The -b option causes SDIF to display inserted or deleted lines consisting
only on blanks or tabs.  By default SDIF does not display such lines
unless the -v option is in effect.

If the -v option is present, each line of file1 is printed, preceded by its
position in file1 and its position in file2 if the line also appears in file2.  If
the -v option is not present, only lines which are present in one file but not
the other are printed.

All output is sent to the standard output stream and may be redirected on
the command line.



CHAPTER 9  CPP REFERENCE


CPP is a preprocessor for the C language which has been included as an
extensive example of how to use Sherlock macros.  CPP fully implements
the draft ANSI standard of January 11, 1988.  For a complete discussion
of what CPP does read section 3.8 of the draft standard.  A more general
discussion of what CPP does can be found in the book, The C
Programming Language, by Brian W. Kernighan and Dennis M. Ritchie,
published by Prentice-Hall.

Basically, CPP copies an input file to an output file doing the following as
it does so:

o It includes files whenever it sees an include directive.  Included files may
themselves contain include directives, which may be nested to any depth.

o It expands macros.  Macros may have arguments and may be call other
macros.

o It conditionally includes lines based on whether symbols have been
defined or on the value of constant expressions. The directives used for
this purpose may be nested to any depth.

o It eliminates all white space, including comments, thereby reducing the
size of the output. White space can be included in the output using a
command line option.

Invoke CPP as follows:

    CPP input_file  output_file  [options]

Options are one of the following:


-c

Include comments and white space in the output file.


-d    <id>=<string>

Define an identifier as if a define directive appeared before the first line of
the program.  For example:

    CPP  in  out  -d  a=xyz

The last example defines the macro a to have the replacement text xyz.  The
equal sign is not part of the replacement text.  If the equal sign and
replacement text are omitted, a null definition is created.  For example, the
following is valid:

    CPP  in  out  -d  a

One or more spaces are required following the -d argument and spaces are
prohibited around the equal sign.  In other words, the -d and a=5 are two,
and only two, separate command line arguments.


-n

Allow nested comments. For example, the following is a nested comment
which is valid only when using the -n option.

    /*comment out - - - - -
        a = 5;
        /* This is a nested comment. */
        b = 5;
    - - - - - end comment out */



-s    <path>

Add a path to the list of "standard places" which is used when searching
for included files.
For example:

    CPP  in  out  -s  \src  -s  \etc

adds the directories called \src and \etc to the end of the list of standard
places.  Initially, the list of standard places is obtained by reading the
INCLUDE environment variable.  For example:

    set INCLUDE=c:\include;c:\usr\include

causes the list of standard places to contain c:\include and c:\usr\include.


-u    <id>

Cancel the initial definition of a macro.  For example,

    CPP in out -u SHERLOCK

cancels the effect of the first definition of the macro called SHERLOCK,
just as if that definition had been immediately followed by

    #undef SHERLOCK



APPENDIX A: RUN TIME ERROR MESSAGES


This appendix lists the error messages that are generated by the support
routines in the file sherlock.c.  You will encounter these messages only
while you are running a program containing Sherlock macros, never
while compiling.  There are two sources of errors that will produce these
messages: faulty Sherlock command line arguments and faulty tracepoint
names in Sherlock macros.  The following abbreviations will be used in
the explanation of these error messages:

    <addr>     The hexadecimal address where the error occurred.
    <char>     A single character, printed in %c format.
    <name>     The name of the macro, i.e., TICK, TRACE, etc.
    <on_prefix>      The on_prefix parameter to the SL_PARSE macro.
    <off_prefix>     The off_string parameter to the SL_PARSE macro.
    <string>     The string representing the tracepoint name.


sl_check:<name>: null string @ <addr>.

The tracepoint name passed to a macro was the NULL string.


sl_check:<name>: bad character <char> in <string> @ <addr>.

The tracepoint name of a macro contains an invalid character.  Only
the following characters are valid in tracepoint names:

o The letters a through z and A through Z.
o The numerals 0 through 9.
o The underscore character.
o The wildcard characters * and ? (on the command line only.)


sl_check: <name>: run on argument: <string> @ <addr>.

The tracepoint name passed to a macro contained more than 25 characters.


sl_init: Header version does not match run-time version.

The version of the macros in the file sl.h or sl1.h does not match the
version of the code in the file sherlock.c.  Change either the version of
the header file that you use to compile your programs or the version of
the support routines that are linked with your program.


sl_ret:  Entry/Exit mismatch at exit point <string>.
Check for missing or misnamed exit macros.
Dump of call stack:

The tracepoint name passed to an exit macro does not match the
tracepoint name on top of the timing stack.  This indicates that name of
the most recently executed entry macro does not match the name of the
current exit macro.  As an aid in finding out where the problem occurred,
the tracepoint names on the call stack are printed out.


Lone <on_prefix>

The on_prefix appeared alone on the command line.  It must be
followed immediately with no intervening spaces by a tracepoint name.
This command line error  immediately terminates the program.


Lone <off_prefix>

The off_prefix appeared alone on the command line.  It must be followed
immediately with no intervening spaces by a tracepoint name. This
command line error  immediately terminates the program.


Trace table overflow.

Too many tracepoint names were encountered during execution of your
program.  Different tracepoints with the same names do not add to this
total.  Neither do tracepoints that are never executed.

To increase the maximum allowable number of tracepoint names, increase
the MAX_STAT variable in sherlock.c and recompile sherlock.c.  To
decrease the number of tracepoint names used by your program,  undefine
SHERLOCK in one or more of your source files and recompile those files.

The tracing tables used by Sherlock are statically allocated so they do not
interfere with the tracing of routines that do dynamic storage allocation.