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Date: Sat, 8 Jun 2002 04:16:12 -0400 (EDT)
From: <librik AT panix DOT com>
Message-Id: <200206080816.g588GCs21659@panix1.panix.com>
To: cygwin AT cygwin DOT com
Subject: Re: 1.3.10:  Bug:  -undef does not work in cpp (gcc 2.95.3-5)

I wrote:
>   The -undef flag, "do not predefine any macros," fails in CPP (GCC)
> for Cygwin.  This is version 2.95.3-5 of GCC.
>   This flag is supposed to invoke the preprocessor without any built-in
> macros defined.  Cygwin's special CPP defines several macros which
> rewrite Microsoft keywords (such as __cdecl and __declspec) to GCC form
> (using the __attribute__ syntax).  The -undef flag fails to undefine any
> of these automatically defined CPP macros.

Heribert Dahms responded:
> did you have a look into the specs file
> /usr/lib/gcc-lib/i686-pc-cygwin/2.95.3-5/specs ?

This specs file seems to contain the same information as the
source file /usr/src/gcc-2.95.3-5/gcc/config/i386/cygwin.h
(is it generated from the .h file during the build process
for gcc, or is it sort of redundant?)

But since it's easier to make changes to the specs file,
I was able to determine the fix to the -undef bug in GCC.

Fix: wrap "%{!undef:" and "}" around the CPP_SPEC in /usr/src/
gcc-2.95.3-5/gcc/config/i386/cygwin.h and also (unless the
specs file is autogenerated) in /usr/lib/gcc-lib/i686-pc-cygwin/
2.95.3-5/specs.

Here is a unified diff patch for cygwin.h:

--- cygwin.h    Sat Jun 08 02:56:05 2002
+++ cygwin.h.old        Sun Jun 17 19:57:59 2001
@@ -91,26 +91,26 @@
    predefined attributes later on.  This can be solved by using one attribute,
    say __declspec__, and passing args to it.  The problem with that approach
    is that args are not accumulated: each new appearance would clobber any
    existing args.  */

 #undef CPP_SPEC
-#define CPP_SPEC "%{!undef:%(cpp_cpu) %{posix:-D_POSIX_SOURCE} \
+#define CPP_SPEC "%(cpp_cpu) %{posix:-D_POSIX_SOURCE} \
   -D__stdcall=__attribute__((__stdcall__)) \
   -D__cdecl=__attribute__((__cdecl__)) \
   %{!ansi:-D_stdcall=__attribute__((__stdcall__)) \
     -D_cdecl=__attribute__((__cdecl__))} \
   -D__declspec(x)=__attribute__((x)) \
   %{mno-win32:%{mno-cygwin: %emno-cygwin and mno-win32 are not compatible}} \
   %{mno-cygwin:-D__MSVCRT__ -D__MINGW32__ %{mthreads:-D_MT} "\
     MINGW_INCLUDES "} \
   %{!mno-cygwin:-D__CYGWIN32__ -D__CYGWIN__ %{!ansi:-Dunix} -D__unix__ -D__unix"\
     CYGWIN_INCLUDES "}\
   %{mwin32|mno-cygwin:%{!ansi:-DWIN32 -DWINNT -D_WIN32} -D_WIN32 -D__WIN32 -D__WIN32__}\
   %{!mno-win32:" W32API_INC "}\
-}"
+"

 #undef CPLUSPLUS_CPP_SPEC
 #define CPLUSPLUS_CPP_SPEC "\
   %{!mno-cygwin:" CYGWIN_CPP_INCLUDES "}\
   %{mno-cygwin:" MINGW_CPP_INCLUDES "}\


Make the same change to the *cpp entry in "specs".

But is this all?  Are there other specs strings that should be changed
to fix this bug as well?  I'd like to ask a GCC expert ... D.J. Delorie,
where are you?

- David Librik
librik AT panix DOT com

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