Building rules_m4 on Windows result in errors

[robin-thomas]

Bazel building using MSVC

$ bazel build @bazelify_gmp//:gmp
INFO: Invocation ID: 18ac6ddd-788d-4f38-b1f5-edd31178d40d
Loading:
Loading: 0 packages loaded
Analyzing: target @bazelify_gmp//:gmp (0 packages loaded, 0 targets configured)
INFO: Analysed target @bazelify_gmp//:gmp (0 packages loaded, 0 targets configured).
INFO: Found 1 target...
[0 / 21] no action
ERROR: C:/users/houji/_bazel_houji/6dp3edvb/external/m4_v1.4.18/BUILD.bazel:15:1: C++ compilation of rule '@m4_v1.4.18//:m4_lib' failed (Exit 2)
c:\users\houji\_bazel_houji\6dp3edvb\execroot\__main__\external\m4_v1.4.18\lib\freadahead.h(41): error C2061: syntax error: identifier '__attribute__'
c:\users\houji\_bazel_houji\6dp3edvb\execroot\__main__\external\m4_v1.4.18\lib\freadahead.h(41): error C2059: syntax error: ';'
Target @bazelify_gmp//:gmp failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 1.788s, Critical Path: 0.70s
INFO: 0 processes.
FAILED: Build did NOT complete successfully
FAILED: Build did NOT complete successfully

Bazel building using mingw-gcc

$ bazel build @bazelify_gmp//:gmp --compiler=mingw-gcc
INFO: Invocation ID: 768ff9c7-3663-4166-a1a0-24d2444af630
Loading:
Loading: 0 packages loaded
Analyzing: target @bazelify_gmp//:gmp (0 packages loaded, 0 targets configured)
INFO: Analysed target @bazelify_gmp//:gmp (0 packages loaded, 0 targets configured).
INFO: Found 1 target...
[0 / 17] no action
ERROR: C:/users/houji/_bazel_houji/6dp3edvb/external/m4_v1.4.18/BUILD.bazel:15:1: C++ compilation of rule '@m4_v1.4.18//:m4_lib' failed (Exit 1)
In file included from external/m4_v1.4.18/lib/regex.c:68:
external/m4_v1.4.18/lib/regex_internal.h:29:10: fatal error: langinfo.h: No such file or directory
 #include <langinfo.h>
          ^~~~~~~~~~~~
compilation terminated.
Target @bazelify_gmp//:gmp failed to build
Use --verbose_failures to see the command lines of failed build steps.
INFO: Elapsed time: 1.267s, Critical Path: 0.21s
INFO: 0 processes.
FAILED: Build did NOT complete successfully
FAILED: Build did NOT complete successfully

It builds fine on Ubuntu and Mac.

Kindly help.

[jmillikin]

I don't have any machines running Windows, so I can't debug this directly. Once rules_m4 moves upstream into the bazelbuild/ org and gets a full CI suite, fixing the Windows build will be more practical.

If you upload the header files generated by m4's build scripts, I might be able to hack something together for the short term. Can you try downloading https://ftp.gnu.org/gnu/m4/m4-1.4.18.tar.xz and running its configure manually, then uploading the resulting config.h and configmake.h to this issue? Ideally once for MSVC, and again using mingw-gcc.

[jmillikin]

MSVC builds are now working. There are some compiler warnings about invalid conversions because M4 assumes sizeof(int) == sizeof(void*) which isn't true, but the resulting binaries are functional enough to pass the test suite.

I haven't tried building with MinGW, but believe it should need only minimal changes. Specifically the use of MSVC-specific #pragma include_alias in gnulib_windows_config.h should be replaced by shim headers containing GCC-specific #include_next directives.