mame: 0.226 build fails on 10.8, due to C header /usr/include/xlocale/_stdio.h, snprintf_l(), etc

[mascguy (Christopher Nielsen)]

Mame 0.226 fails to build on 10.8, due to compilation errors in file 'src/osd/modules/files/posixfile.cpp'.

Here's one example:

In file included from ../../../../../src/osd/modules/file/posixfile.cpp:41:
In file included from ../../../../../src/osd/modules/file/posixfile.h:12:
In file included from ../../../../../src/osd/osdcore.h:17:
In file included from ../../../../../src/lib/util/strformat.h:174:
In file included from ../../../../../src/lib/util/vecstream.h:25:
In file included from /opt/local/libexec/llvm-9.0/bin/../include/c++/v1/istream:163:
In file included from /opt/local/libexec/llvm-9.0/bin/../include/c++/v1/ostream:140:
/opt/local/libexec/llvm-9.0/bin/../include/c++/v1/locale:1455:16: error: use of undeclared identifier 'snprintf_l'; did you mean 'vswprintf_l'?
    int __nc = __libcpp_snprintf_l(__nar, sizeof(__nar), _LIBCPP_GET_C_LOCALE, __fmt, __v);
               ^

Root cause appears to be preprocessor logic within C header file /usr/include/xlocale/_stdio.h, determining whether additional stdio functions are defined. One of those being snprintf_l().

Findings:

• In later MacOS/Xcode releases, the logic is #if __DARWIN_C_LEVEL >= 200112L || defined(__cplusplus). The latter condition ensures we don't have to worry about _DARWIN_C_LEVEL.
• But under MacOS 8.x, the logic is simply #if __DARWIN_C_LEVEL >= 200112L, with no awareness of C++ code. This breaks the Mame build.

For now, patching Mame source file posixfile.cpp is the easy fix. We simply have to appropriately define __DARWIN_C_LEVEL, or _DARWIN_C_SOURCE. I can confirm that the latter works, and the former certainly should as well.

Note: I'd prefer not to globally define anything, since the issue is limited to a single source file. There's too much risk, and it's simply not needed elsewhere.

[mascguy (Christopher Nielsen)]

<After additional investigation, this comment no longer relevant.>

[ryandesign (Ryan Carsten Schmidt)]

MacPorts uses libc++ by default on 10.6 and later. Are you sure that mame is using libstdc++? If it is, that is a bug that should be fixed; it should use the C++ stdlib that MacPorts tells it to.

[mascguy (Christopher Nielsen)]

Replying to ryandesign:

MacPorts uses libc++ by default on 10.6 and later. Are you sure that mame is using libstdc++? If it is, that is a bug that should be fixed; it should use the C++ stdlib that MacPorts tells it to.

No, you're right... Mame is using libc++, rather than libstdc++.

However, more digging revealed this to be a C header file issue... completely unrelated to the C++ standard library.

[mascguy (Christopher Nielsen)]

In addition to verifying the build fix, I've also confirmed that Mame runs successfully on MacOS 10.8.5.