Odd compile error with RES_STARTEND and regex.h version on MSVC build

[jeffhostetler]

I think I've found a problem in the Makefile for v2.27.0. (I haven't tracked it back to when it first appeared yet.)

Basically, when building the MSVC version (using make MSVC=1 DEBUG=1) I'm seeing an error

...
fuzz-commit-graph.c
C:\work\msft\git-compat-util.h(1135): fatal error C1189:
    #error:  "Git requires REG_STARTEND support. Compile with NO_REGEX=NeedsStartEnd"
...

However, we're already defining that symbol in config.mak.uname in the MSVC section.

Hacking the Makefile to include -E and looking at the CPP output shows that the compiler is
finding the wrong version of regex.h. It is finding:

...
__pragma(pack(pop))
#line 189 "C:\\work\\msft\\git-compat-util.h"
#line 1 "C:\\git-sdk-64\\mingw64\\include\\regex.h"
...

and NOT the one in ./compat/regex/regex.h

Note that the MSVC section in config.mak.uname is adding -Icompat -Icompat/regex to COMPAT_FLAGS at https://github.com/microsoft/git/blob/vfs-2.27.0/config.mak.uname#L451 (and later again at https://github.com/microsoft/git/blob/vfs-2.27.0/Makefile#L1793 )

Later, COMPAT_CFLAGS gets appended to BASIC_CFLAGS at https://github.com/microsoft/git/blob/vfs-2.27.0/Makefile#L2004

BUT At https://github.com/microsoft/git/blob/vfs-2.27.0/Makefile#L1357-L1381
(and when CURLDIR is mingw64) we append -I/mingw64/include to BASIC_CFLAGS,
but this happens before COMPAT_CFLAGS is appended.

Therefore, the compiler sees ... -I/mingw64/include -Icompat -Icompat/regex ...
and tries to use the wrong version of regex.h which leads to the compiler error.

I'm not sure if this problem is unique to a conflict with CURL. It looks like it Expat, ZLib,
IConv, and a few others could similarly update BASIC_CFLAGS before the values from
COMPAT_CFLAGS are brought in.

Thoughts??

[jeffhostetler]

jeffhostetler@7533abb

This the -E hack. Use it with make MSVC=1 DEBUG=1 CFLAGS="-E".
I'm not creating a PR for this now, since the real fix should be upstream rather than here.
And this hack could go with it.

[dscho]

Where does that -I/mingw64/include come from? That should not be there, MSVC cannot handle those headers.

[jeffhostetler]

Either of these lines, I think.
https://github.com/microsoft/git/blob/vfs-2.27.0/Makefile#L1366
https://github.com/microsoft/git/blob/vfs-2.27.0/Makefile#L1379

Here's what I get when I look at curl-config:

$ curl-config --cflags
-I/mingw64/include

So we get that stuck into CURL_CFLAGS and that gets appended onto BASIC_CFLAGS
at https://github.com/microsoft/git/blob/vfs-2.27.0/Makefile#L1381 .

[jeffhostetler]

So the resulting command line looks like this. I suggest that the -I is coming from the
CURL block because it appears between the HAVE_ALLOCA_H and the USE_CURL_FOR_IMAP_SEND terms.

www.txt:8040:compat/vcbuild/scripts/clink.pl -o fuzz-commit-graph.o -c
-nologo -I. -Icompat/vcbuild/include -DWIN32 -D_CONSOLE -DHAVE_STRING_H
-D_CRT_SECURE_NO_WARNINGS -D_CRT_NONSTDC_NO_DEPRECATE -I"C:\work\msft\compat\vcbuild\vcpkg\installed\x64-windows\include"
-I"C:/Program Files (x86)/Windows Kits/10/Include/10.0.18362.0/ucrt"
-I"C:/Program Files (x86)/Windows Kits/10/Include/10.0.18362.0/um"
-I"C:/Program Files (x86)/Windows Kits/10/Include/10.0.18362.0/shared"
-I"C:/Program Files (x86)/Microsoft Visual Studio/2019/Enterprise/VC/Tools/MSVC/14.26.28801/INCLUDE"
-L"C:\work\msft\compat\vcbuild\vcpkg\installed\x64-windows\debug\lib"
-L"C:/Program Files (x86)/Windows Kits/10/lib/10.0.18362.0/ucrt/x64"
-L"C:/Program Files (x86)/Windows Kits/10/lib/10.0.18362.0/um/x64"
-L"C:/Program Files (x86)/Microsoft Visual Studio/2019/Enterprise/VC/Tools/MSVC/14.26.28801/lib/x64"
-Zi -MDd -DDEBUG -D_DEBUG -DGIT_HOST_CPU="\"x86_64\""
-DHAVE_ALLOCA_H -I/mingw64/include -DUSE_CURL_FOR_IMAP_SEND -DNO_ST_BLOCKS_IN_STRUCT_STAT
-DNO_SYMLINK_HEAD -DNO_GETTEXT -DNO_POLL_H -DNO_SYS_POLL_H -DNO_INTTYPES_H -DMMAP_PREVENTS_DELETE
-DNO_IPV6 -DNO_UNIX_SOCKETS -DNO_POSIX_GOODIES -DSHA1_DC -DSHA1DC_NO_STANDARD_INCLUDES
-DSHA1DC_INIT_SAFE_HASH_DEFAULT=0 -DSHA1DC_CUSTOM_INCLUDE_SHA1_C="\"cache.h\""
-DSHA1DC_CUSTOM_INCLUDE_UBC_CHECK_C="\"git-compat-util.h\"" -DSHA256_BLK  -DUNRELIABLE_FSTAT
-DNATIVE_CRLF -DHAVE_WPGMPTR -D__USE_MINGW_ACCESS -DDETECT_MSYS_TTY -DENSURE_MSYSTEM_IS_SET
-DNOGDI -DHAVE_STRING_H -Icompat -Icompat/regex -Icompat/win32 -DSTRIP_EXTENSION=\".exe\"
-DNO_LIBGEN_H -DNO_POLL -Icompat/poll -DNO_STRCASESTR -DNO_STRLCPY -DNO_STRTOUMAX -DNO_SETENV -DNO_MKDTEMP
-DUSE_WIN32_MMAP -DOBJECT_CREATION_MODE=1 -DNO_PREAD -DNO_MEMMEM
-DRUNTIME_PREFIX -Icompat/regex -DSHELL_PATH='"/bin/sh"' -DDEFAULT_HELP_FORMAT='"html"'
-DPAGER_ENV='"LESS=FRX LV=-c"'
fuzz-commit-graph.c

[dscho]

[...] it appears between the HAVE_ALLOCA_H and the USE_CURL_FOR_IMAP_SEND terms.

Ah, it's most likely caused by https://github.com/git-for-windows/git/blob/v2.27.0.windows.1/Makefile#L1374.

As this was kind of intentional, maybe our best bet is to add an if clause before https://github.com/git-for-windows/git/blob/v2.27.0.windows.1/compat/vcbuild/scripts/clink.pl#L26 that skips -I/mingw{32,64}/...?