Simtel MSDOS - Coast to Coast/simteldosarchivecoasttocoast2.iso/djgpp/djgpp.faq

Text File | 1994-03-07 | 14KB | 258 lines

Q: What's the minimum set of .zip files I need for compiling programs?
A: djeoeXXX, djdevXXX, gccXXXbn, gasXXXbn, and bnuXXbn are required.  The
   remainder are for additional functionality.  Note that the version
   numbers do not neccessarily match between FSF programs (gas and gcc)
   and my programs (go32).  You'll also need bsnXXXbn for bison and
   flxXXXbn for flex, where XXX is the version number.

   Note that C++ requires gppXXX.zip, and ObjectiveC requires objcXXX.zip.
   The C++ library includes obstacks, alloca, and regex, so you need to
   get gppXXX.zip to use them (libgpl.a)

Q: What about documentation?
A: Get txiXXX.bn, which includes INFO.EXE.  Unpack it and run "info".  It
   will bring up a (hopefully) self-explanatory online help system.

   For go32 and programs I wrote, get djdocXXX.zip, which includes the
   data files for the online help system.

   For the FSF utilities, djgpp includes three files each.  Example:
    gcc254bn.zip - binaries & source diffs for gcc 2.5.4
    gcc254dc.zip - documentation for gcc 2.5.4
    gcc254sr.zip - original FSF sources for gcc 2.5.4

   (Some sources are too big, and are split into multiple zips, all
   of which must be unzipped to get a complete source distribution:
        gcc254s1.zip
        gcc254s2.zip
        gcc254s3.zip
   All sources are shipped in ready-to-build form.  The diffs in
   the diffs directory have already been applied.)

Q: How do I find out what go32 is doing?
A: The first thing to do is run "go32".  It will give you gobs of
   information about what it knows about your system and itself.
   Next, set the "topline" flag in the GO32 environment varable
   (see the README) and watch the top line of your screen.  The
   info there tells you something about what the program is doing.

Q: I get errors I can't figure out when I try to compile something.
A: The best way to figure out what's going wrong with gcc is to
   use the "-v" switch.  For example, if you run "gcc -v hello.c"
   (assuming you have hello.c), it will tell you all the programs
   it is running.  Then, you can see which program caused the
   error.  The most likely cause of errors relating to missing
   programs is that you haven't unpacked the zip file with
   one of the compiler passes or utilities on it.

Q: Why do I get so many unresolved symbols when linking C++ programs?
A: The C++ libraries are not in libc.a, which is the only default
   library.  You must use a command like this:
       gcc -o prog prog.o -lgpp -lm
   Note that some C++ classes use math routines, so the -lm should be
   given after the -lgplus.  If you don't link with -lgpl or -lgpp,
   you won't include any GPL code in your application.  You may not
   need all of these libraries for your program.

Q: How do I debug my programs?
A: First, remember to use the -g switch when you compile.  This puts debugging
   information into your executable.  Then, to debug the program, use a
   command line like this:
      go32 -d edebug32 myprog
   "edebug32" is the external debugger.  See the file "edebug32.doc" for
   information on the debugger commands.  Note: if you are running in a
   DPMI environment, you must use "ed32-dpmi" instead of "edebug32".  Go32
   normally searches relative to the current directory, then from it's own
   directory, then the PATH, for the external debugger program.

Q: When I run my programs under Windows, they crash, but not outside of
   Windows.
A: You may have used the "-fomit-frame-pointer" option to GCC.  This
   tells gcc that it can use EBP as a general register.  However, the
   segment used for the stack is protected against access outside of
   calculated stack range, and EBP causes the stack selector to be used.
   If you use this to access memory in the regular data area, you get
   a protection fault.  This mechanism is present to prevent you from
   using so much stack that you begin corrupting data.  Outside of
   Windows, a different method is used to detect stack overrun, so you
   don't see this fault.

Q: How do I create symbolic links?
A: Copy bin/stub.exe to the name of the link you want.  In this example,
   let's say the real program is dj1.exe and we want to make a link called
   dj2.exe that really calls dj1.exe.  We'd copy stub.exe to dj2.exe.
   Next, run stubedit to modify the new programs' stub info block to change
   the name of the executable it runs.  In this case, we'd change it to
   dj1.  When you run dj2 now, it tells go32 to use the image of dj1.
     C:\> copy c:\djgpp\bin\stub.exe c:\usr\bin\dj2.exe
     C:\> stubedit c:/usr/bin/dj2.exe runfile=dj1

Q: When I run "gcc e:\proj\prog.c" it says "undefined escape sequence \p"?
A: Gcc is a *unix* compiler - you must use *unix* slashes (e:/proj/prog.c).
   Environment variables (like GCCINC) may, however, use either, as they
   are converted.

Q: I type "GCC PROG.C" and ld complains about PROG.C not being an object.
Q: I type "gcc prog.cxx" to compile a C++ program, and ld complains.
A: Gcc is *not* case insensitive like DOS is, and it uses the file's
   extension to determine how to compile a file.  Valid extensions are:
     .cc = C++ source (passed through cpp)
     .c = C source that must be passed through cpp first
     .i = raw C source (no cpp pass)
     .S = assembler that must be passed through cpp first
     .s = raw assembler source (no cpp pass)
   any other file is passed to the linker

Q: I compile my program, but can't run the output file.
A: DOS doesn't know how to run unix-style COFF files.  That's what the
   extender is for.  To run an COFF file called myprog, type
     "go32 myprog . . ."

Q: I compile my program, but when I run the .exe it hangs.
A: Most likely, you did this: "gcc foo.c -o foo.exe".  This doesn't
   create a real .EXE file.  That's like renaming your phone directory
   file to an .EXE and expecting it to run.  You must use the COFF2EXE
   program to convert the output of gcc to a real executable.

Q: Gcc doesn't recognize // as a comment in my C programs.
A: That's because // isn't a comment in C.  If you want to compile C++,
   then write C++ programs.  Gcc is really two compilers in one, not
   one compiler that compiles both C and C++.  That's why you get
   cc1 and cc1plus.

Q: I'm reading in data files, but the data gets corrupted.
A: The default file type is DOS text, even for read() and write().  You must
   tell the system that a file is binary through the "b" flag in fopen(),
   or O_BINARY in open() or setmode().

Q: I get "fatal signal 2" when I run gcc.
A: When gcc reports a "signal", it really means that an error occurred
   trying to run the given program.  The "signal" number is the DOS error
   code, and 2 means "file not found".  Check the COMPILER_PATH environment
   variable and make sure it points to the directory with cpp.exe,
   cc1.exe, etc.

Q: The binaries I get with the distribution are .exe files, but gcc creates
   COFF files.  I rename the COFF's to .EXE's, but they still don't work.
A: To get an .EXE from an COFF, you must *prepend* either go32.exe
   or stub.exe to the file.  A program called "coff2exe" is provided to
   do this.  Just run "coff2exe myprog".

Q: What is stub.exe?
A: Stub.exe simply calles go32.exe, and passes it information it needs to
   run the COFF file attached to it.  Stub is much smaller than go32, so
   less disk space is used.  Also, if you change go32, you don't have to
   change stub, and all the stub-ized programs will use the new go32
   automatically.

Q: I want to change cc1.  How do I do this?
A: First, get the GNU sources.  These should be the "gccXXXsr.zip"
   files found in the djgpp distribution.  You can also get the latest
   versions from the FSF if you like.  They're usually available at
   prep.ai.mit.edu in /pub/gnu, if not elsewhere.  djgpp includes a
   copy of gzip (gzp124bn.zip) that can uncompress them. Use
   djtarx to un-tar them, as djtarx knows how to handle unix file names
   that aren't valid DOS file names.  Next, apply the "diffs" (if any)
   over the GNU sources (making sure you have the right version of GNU
   - see the versions file).  For most GNU utilities, you must run
   "configure" to prepare the sources for a native go32 build before
   building. For all other programs, just run make. Note that the makefiles
   are tuned for gnu make, since it knows how to handle long command lines.
   Specific instructions are documented in the diffs or in each program's
   configure.bat.

Q: I don't have an 80387.  How do I compile floating point programs?
A: Add "emu c:\djgpp\bin\emu387" to the GO32 environment variable
   (see go32 section in readme).  This tells go32 to use the given file
   as an 80387 emulator.  If you don't load this emulator, and you try
   to run floating point without a 387, you will get an error.

Q: I installed an 80387 emulator in my AUTOEXEC, but it still doesn't
   work.  Why?
A: The CPU is running in *protected* mode, not real mode, and the information
   needed to emulate the 80387 is different.  Not to mention that the
   exceptions never get to the real-mode handler.  You must use the emu387
   emulator, which is designed for go32.

Q: Can I run this on my 286?  It has protected mode also...
A: True, but the 286 isn't a 32-bit processor.  A 386 really is required.

Q: Can I use gcc on my 512K machine?
A: Yes, but the disk better have at least 4Mb of free space for paging.
   Go32 will use all available extended memory (up to 128M) and up to
   128M of disk space, for a grand total of 256M of virtual memory for
   your application.  Try a malloc(50*1024*1024) some day.

Q: Why do my compiles are running VERY SLOW, even though I use a ramdisk
   for swap and a disk cache?
A: Gcc requires at least 1Mb of virtual memory to run, usually close to 1.5M.
   If there isn't this much real memory available, it starts paging to disk.
   It's good to leave about 1M of extended (not expanded) memory available
   for go32 to run programs with.  When it needs to page a lot, you spend
   most of your time paging and little time actually running.  Note that
   if you are running with a VCPI server, like QEMM or 386MAX, then go32
   will use *expanded* memory for it's physical memory needs, not
   extended.

Q: How much memory is available when I use the system() call?
A: Everything but what go32 is loaded with.  The program is completely
   paged out to memory (including the page tables themselves) before
   the second program is executed.  Currently, this is about 100K
   less than was available before go32 was executed.

Q: Go32 complains that the CPU must be in V86 mode to run.
A: When the CPU is in V86 mode, the V86 manager must provide VCPI
   services for go32.  Since VCPI is an extension to EMS, disabling EMS
   will disable VCPI, and prevent go32 from running.  For some EMS
   managers, this means that you can't use the "noems" switch.

Q: Why can't I keep QEMM in auto/off mode?
A: When QEMM is in auto/off mode and there isn't anything in the system that
   is using any of QEMM's features, the CPU remains in "real" mode.  Go32
   knows this, and will try to use XMS to access the extended memory.
   Unfortunately, XMS is a feature that causes QEMM to turn on, and go32
   doesn't know this and when it tries to switch into protected mode,
   QEMM traps it and gives a protection violation warning.  Since this
   always requires a system reboot to fix, go32 checks to see if enabling
   XMS caused the cpu to switch into v86 mode (meaning QEMM just turned
   on) and gracefully exits.  All you have to do to work around this is
   force QEMM to be on all the time so that go32 will know how to work
   with it properly.

Q: How do globbing and response files work?
A: A response file is a file that contains stuff that goes on the command
   line, but is too big for DOS.  The name of the file is given as "@file"
   to any COFF program, and go32 reads the file for command line
   information.  It uses single and double quotes to group parameters, and
   backslashes to escape quotes, spaces, tabs, newlines, and backslashes.
   Parameters containing wildcards are expanded if they can be, else they
   are unmodified.  Surrounding a parameter in single quotes will prevent
   wildcards from being expanded.  This is similar to unix.  Note that
   backslashes are not special if they are not in front of a quote,
   whitespace, or backslash.

Q: What is GCC-RM?  How do I use it?
A: GCC is merely a driver program which calls the CCP, CC1, AS, LD images.
   The real-mode gcc is simply gcc itself compiled with Turbo-C instead of
   Gcc.  This improves compile times on most systems, but isn't as
   "clean" as the 32-bit compiled version, and also the 32-bit version
   can be recompiled (FSF desires) without having to purchase a new
   compiler.  Both versions should produce exactly the same output, but
   if you have any problems (such as under Novell) use the 32 bit version.
   You can either put GCC-RM in your path and issue GCC as your compile
   command, or copy it to the bin directory (saving the 32 bit GCC.EXE first).
   GCC-RM does not create 16 bit code, or allow the compiler to work on
   16 bit only machines.

Q: Is GDB available for DJGPP?
A: No, but if you'd like to work on porting it, let me know :-)

Q: Where is the "make" utility?
A: mak369bn.zip contains the make utility.

Q: Why can't I get segment registers to work in go32 programs?
A: Because segments work differently in protected mode.  For most cases, you
   will not need to use segments.  The "small" model allows up to
   2 Gb of data space before you run out, so there's no need
   for far pointers anyway.