[bug-diffutils] bug#64811: Win-version now broken

[Bruno Haible]

Paul Eggert wrote:
> I don't use MS-Windows and won't be of much help on that platform.
> ...
> A few minutes ago I also installed a patch that causes diff -r to use 
> readlinkat instead of readlink

I took a stab at it and attempted to compile diffutils with mingw 10.0.0
and with MSVC 14.30. Here are the compilation errors and link errors that
I encountered. I'm attaching a fix for all issues. With it, the build
succeeds, and there are
  - 13 test failures on mingw,
  - 14 test failures on MSVC.

1) A compilation error (both mingw and MSVC):

../../lib/cmpbuf.c: In function 'block_read':
../../lib/cmpbuf.c:87:17: error: 'SA_RESTART' undeclared (first use in this 
function)
   87 |           if (! SA_RESTART && errno == EINTR)
      |                 ^~~~~~~~~~

This is fixed by adding 'sigaction' to the list of gnulib modules.

2) A compilation error (both mingw and MSVC):

../../src/util.c: In function 'process_signals':
../../src/util.c:277:17: error: 'SIGSTOP' undeclared (first use in this 
function)
  277 |           sig = SIGSTOP;
      |                 ^~~~~~~

This is fixed by adding the same '#ifdef SIGTSTP' in the stop signal processing
as elsewhere in the file.

3) A compilation error (both mingw and MSVC):

../../src/util.c:308:5: error: 'SIGHUP' undeclared here (not in a function)
  308 |     SIGHUP, SIGINT, SIGPIPE,
      |     ^~~~~~
../../src/util.c:308:21: error: 'SIGPIPE' undeclared here (not in a function); 
did you mean 'SIGFPE'?
  308 |     SIGHUP, SIGINT, SIGPIPE,
      |                     ^~~~~~~
      |                     SIGFPE

This is fixed by adding #ifdefs for the use of these signal names.
For SIGPIPE, an alternative would be to use the gnulib module 'signal-h',
but that feels like overkill here.

4) A compilation error (mingw) or link error (MSVC):

../../src/diff.c: In function 'compare_files':
../../src/diff.c:1412:58: error: 'readlinkat' undeclared (first use in this 
function); did you mean 'careadlinkat'?
 1412 |                                                 nullptr, readlinkat);
      |                                                          ^~~~~~~~~~
      |                                                          careadlinkat

This is fixed by adding 'readlinkat' to the list of gnulib modules.

5) Link errors (on MSVC):

diff3.obj : error LNK2019: unresolved external symbol popen referenced in 
function read_diff
diff3.obj : error LNK2019: unresolved external symbol pclose referenced in 
function read_diff
sdiff.obj : error LNK2019: unresolved external symbol popen referenced in 
function main
sdiff.obj : error LNK2019: unresolved external symbol pclose referenced in 
function main

This is fixed by adding 'popen' and 'pclose' to the list of gnulib modules.

6) A link error (on MSVC) regarding readdir.

This is fixed by adding 'readdir' to the list of gnulib modules.

7) A link error (on mingw):

/usr/lib/gcc/x86_64-w64-mingw32/11/../../../../x86_64-w64-mingw32/bin/ld: 
../lib/libdiffutils.a(libdiffutils_a-strerror.o): in function `memcpy':
/usr/x86_64-w64-mingw32/sys-root/mingw/include/string.h:202: undefined 
reference to `__memcpy_chk'
/usr/lib/gcc/x86_64-w64-mingw32/11/../../../../x86_64-w64-mingw32/bin/ld: 
../lib/libdiffutils.a(libdiffutils_a-strerror.o): in function `sprintf':
/usr/x86_64-w64-mingw32/sys-root/mingw/include/stdio.h:386: undefined reference 
to `__chk_fail'
/usr/lib/gcc/x86_64-w64-mingw32/11/../../../../x86_64-w64-mingw32/bin/ld: 
../lib/libdiffutils.a(libdiffutils_a-localcharset.o): in function `strcpy':
/usr/x86_64-w64-mingw32/sys-root/mingw/include/string.h:228: undefined 
reference to `__strcpy_chk'
/usr/lib/gcc/x86_64-w64-mingw32/11/../../../../x86_64-w64-mingw32/bin/ld: 
../lib/libdiffutils.a(libdiffutils_a-localcharset.o): in function `sprintf':
/usr/x86_64-w64-mingw32/sys-root/mingw/include/stdio.h:386: undefined reference 
to `__chk_fail'
collect2: error: ld returned 1 exit status
make[2]: *** [Makefile:2013: cmp.exe] Error 1

Apparently the _FORTIFY_SOURCE support in mingw is experimental. Other
people have noticed it as well:
https://github.com/msys2/MINGW-packages/issues/5868

The fix is to not define _FORTIFY_SOURCE on this platform. Done in
configure.ac.

Bruno

0001-maint-Fix-build-failures-mingw-10-and-MSVC-14.30.patch
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