MSYS2 64-bit's gcc does not define __WIN32__ by default

[abonander]

I'm getting an error for missing symbols in time_helpers.c:

note: D:\Git\img_dup\target\deps\libtime-040b8fe6da930644.rlib(r-time_helpers-time_helpers.o):time_helpers.c:(.text$rust_time_gmtime+0x27): undefined reference to `gmtime_r'
D:\Git\img_dup\target\deps\libtime-040b8fe6da930644.rlib(r-time_helpers-time_helpers.o):time_helpers.c:(.text$rust_time_localtime+0x27): undefined reference to `localtime_r'
ld: D:\Git\img_dup\target\deps\libtime-040b8fe6da930644.rlib(r-time_helpers-time_helpers.o): bad reloc address 0x27 in section `.text$rust_time_localtime'

This is a fresh MSYS2 install, plus gcc grabbed through the included pacman.

It looks like the C preprocessor isn't predefining __WIN32__ unless -mwin32 is passed:

$ gcc -m64 -dM -E -x c /dev/null | grep "WIN"
#define __WINT_MAX__ 4294967295U
#define __WINT_MIN__ 0U
#define __SIZEOF_WINT_T__ 4
#define __CYGWIN__ 1
#define __WINT_TYPE__ unsigned int

$ gcc -mwin32 -dM -E -x c /dev/null | grep "WIN"
#define _WIN32 1
#define __WINT_MAX__ 4294967295U
#define __WINT_MIN__ 0U
#define __WIN32 1
#define __WIN32__ 1
#define __SIZEOF_WINT_T__ 4
#define __CYGWIN__ 1
#define WIN32 1
#define __WINT_TYPE__ unsigned int
#define WINNT 1

Not sure if this belongs here or gcc-rs. Patching time to add the -mwin32 flag for target_os = "windows" did the trick, then I needed to get tchar.h from pacman -S mingw-w64-x86_64-headers and copy it into /usr/include.

[alexcrichton]

It sounds like adding -mwin32 to gcc-rs is a good idea! Want to submit a PR for that?

[abonander]

@alexcrichton PR submitted!

[alexcrichton]

Closing in favor of rust-lang/cc-rs#19, thanks!