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Amiga MA Magazine 1998 #6
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cpp.doc
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CPP(1) Amiga Programmer's Manual CPP(1)
1mNAME
cpp 0m- C Pre Processor. Macro-preprocess C programs.
1mSYNOPSIS
0mcpp [-options] [infile [outfile]]
1mDESCRIPTION
0mCPP reads a C source file, expands macros and include files,
and writes an input file for the C compiler. If no file
arguments are given, CPP reads from stdin and writes to
stdout. If one file argument is given, it will define the
input file, while two file arguments define both input and
output files. The file name "-" is a synonym for stdin or
stdout as appropriate.
The following options are supported. Options may be given
in either case.
-C If set, source-file comments are written to the output
file. This allows the output of CPP to be used as the
input to a program, such as lint, that expects commands
embedded in specially-formatted comments.
-Dname=value
Define the name as if the programmer wrote
#define name value
at the start of the first file. If "=value" is not
given, a value of "1" will be used.
On non-unix and non-amiga systems, all alphabetic text
will be forced to upper-case.
-E Always return "success" to the operating system, even
if errors were detected. Note that some fatal errors,
such as a missing #include file, will terminate CPP,
returning "failure" even if the -E option is given.
-Idirectory
Add this directory to the list of directories searched
for #include "..." and #include <...> commands. Note
that there is no space between the "-I" and the
directory string. More than one -I command is
permitted. On non-Unix systems "directory" is forced
to upper-case.
-N CPP normally predefines some symbols defining the
target computer and operating system. If -N is
specified, no symbols will be predefined. If -N -N is
specified, the "always present" symbols, __LINE__,
__FILE__, __TIME__ and __DATE__ are not defined.
-Stext
CPP normally assumes that the size of the target
computer's basic variable types is the same as the size
of these types of the host computer. (This can be
1st PDC distribution -1-
CPP(1) Amiga Programmer's Manual CPP(1)
overridden when CPP is compiled, however.) The -S
option allows dynamic respecification of these values.
"text" is a string of numbers, separated by commas,
that specifies correct sizes. The sizes must be
specified in the exact order:
char short int long float double
If you specify the option as "-S*text", pointers to
these types will be specified. -S* takes one
additional argument for pointer to function (e.g. int
(*)())
For example, to specify sizes appropriate for a PDP-11,
you would write:
c s i l f d func
-S1,2,2,2,4,8,
-S*2,2,2,2,2,2,2
Note that all values must be specified.
3mNote also that this is not allowed by the 11-Jan-88
Draft, and therefore has made into an option when
compiling Cpp.
0m-Uname
Undefine the name as if
#undef name
were given. On non-Unix systems, "name" will be forced
to upper-case.
-Xnumber
Enable debugging code. If no value is given, a value
of 1 will be used. (For maintenence of CPP only.)
1mPre0m-1mDefined Variables
0mWhen CPP begins processing, the following variables will
have been defined (unless the -N option is specified):
Target computer (as appropriate):
pdp11, vax, M68000 m68000 m68k, amiga m68000
Target operating system (as appropriate):
rsx, rt11, vms, unix, amigados
Target compiler (as appropriate):
decus, vax11c, pdc __PDC__
The implementor may add definitions to this list. The
default definitions match the definition of the host
computer, operating system, and C compiler.
The following are always available unless undefined (or -N
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CPP(1) Amiga Programmer's Manual CPP(1)
was specified twice):
__FILE__ The input (or #include) file being compiled
(as a quoted string).
__LINE__ The line number being compiled.
__DATE__ The date of compilation as a quoted string
of the format "Mmm dd yyyy".
__TIME__ The time of the start of compilation as a
quoted string of the format "hh:mm:ss".
Thus,
printf("Bug at line %s,", __LINE__);
printf(" source file %s", __FILE__);
printf(" compiled on %s %s", __DATE__,
__TIME__);
1mSupported directives
0m#assert <expression>
#define <token> <replacement>
#elif <expression>
#else <expression>
#endif
#error
#if <expression>
#ifdef <token>
#ifndef <token>
#include <filename>
#line <number> <filename>
#pragma <anything>
#undef <token>
#debug
#nodebug
Unsupported # commands are copied verbatim into the output,
so that maybe the compiler knows what to do with them.
1mDraft Proposed Ansi Standard Considerations
0mThe current version of the Draft Proposed Standard
explicitly states that "readers are requested not to specify
or claim conformance to this draft." Readers and users of
Decus CPP should not assume that Decus CPP conforms to the
standard, or that it will conform to the actual C Language
Standard.
When CPP is itself compiled, many features of the Draft
Proposed Standard that are incompatible with existing
preprocessors may be disabled. See the comments in CPP's
source for details.
The latest version of the Draft Proposed Standard (as
reflected in Decus CPP) is dated November 12, 1984, and bits
from K&R V2 are put in by Ois.
Comments are removed from the input text. The comment is
replaced by a single space character. The -C option
preserves comments, writing them to the output file.
The '$' character is considered to be a letter. This is a
permitted extension.
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CPP(1) Amiga Programmer's Manual CPP(1)
The following new features of C are processed by CPP:
#if, #elif
#elif expression (#else #if)
'\xNNN' (Hexadecimal constant)
'\a' (Ascii BELL)
'\v' (Ascii Vertical Tab)
#if defined NAME 1 if defined, 0 if not
#if defined (NAME) 1 if defined, 0 if not
#if sizeof (basic type)
#error Generates error message
unary +
123U, 123LU Unsigned ints and longs.
12.3L Long double numbers
token##token Token concatenation in macros
#macro-formal String generation in macros
#include token Expands to filename
The Draft Proposed Standard has extended C, adding a
constant string concatenation operator, where
"foo" "bar"
is regarded as the single string "foobar". (This does not
affect CPP's processing but does permit a limited form of
macro argument substitution into strings as will be
discussed.)
The Standard Committee plans to add token concatenation to
#define command lines. One suggested implementation is as
follows: the sequence "Token1 ## Token2" is treated as if
the programmer wrote "Token1Token2".
This could be used as follows:
#line 123
#define ATLINE foo ## __LINE__
ATLINE would be defined as foo123.
Note that "Token1" and "Token2" both must be valid tokens,
but the concatenation of their expanded forms may not be a
_single_ valid token. In that case, K&R state that the
behaviour is undefined. So if you wish to make portable use
of this facility, do not do the following:
#define cat(x, y) x ## y
cat(foo, 1.23)
which will produce
foo1.23
and that is not a single token.
If the tokens T1 and T2 are concatenated into T3, this
implementation operates as follows:
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CPP(1) Amiga Programmer's Manual CPP(1)
1. Expand T1 if it is a macro.
2. Expand T2 if it is a macro.
3. Join the tokens, forming T3.
4. Rescan T3, looking for tokens, that may be expanded
again.
A macro formal parameter will be substituted into a
string or character constant if it is the only component of
that constant:
#define VECSIZE 123
#define vprint(name, size) \
printf("name" "[" "size" "] = {\n")
... vprint(vector, VECSIZE);
expands (effectively) to
vprint("vector[123] = {\n");
Note that this will be useful if your C compiler supports
the new string concatenation operation noted above. As
implemented here, if you write
#define string(arg) "arg"
... string("foo") ...
This implementation generates "foo", rather than the
strictly correct ""foo"" (which will probably generate an
error message). This is, strictly speaking, an error in CPP
and may be removed from future releases. 3mNote that the
above feature of replacing macro formals inside quotes is
non-standard. The Committee thought the following to be
better:
0mIf a macro formal argument is immediately preceeded by a #,
the argument supplied when expanding the macro will be
surrounded by double quotes, and each double quote or
backslash will be preceeded by a backslash. An example of
this would be:
#define string(arg) #arg
... string(foo) ...
which produces "foo". Note that this feature is useless if
you want your string to contain an odd number of quotes:
string(Hello");
will produce an error message, complaining about
unterminated strings.
1mError messages
0mMany. CPP prints warning or error messages if you try to use
multiple-byte character constants (non-transportable) if you
#undef a symbol that was not defined, or if your program has
potentially nested comments.
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CPP(1) Amiga Programmer's Manual CPP(1)
1mAuthor
0mMartin Minow, minor changes by RMS, FNF, OIS.
1mBugs
0mThe #if expression processor uses signed integers only.
I.e, #if 0xFFFFu < 0 may be TRUE.
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