v11.0+ fails to build on Amiga and Xbox

[glebm]

fmt from v11.0.0 onwards (6b68dff) no longer builds for Amiga and Xbox, with the same error on both:

fmt/format-inl.h:1638:5: error: 'flockfile' was not declared in this scope
 1638 |     flockfile(f);
      |     ^~~~~~~~~
fmt/format-inl.h: In destructor 'fmt::v11::detail::file_print_buffer::~file_print_buffer()':
fmt/format-inl.h:1646:5: error: 'funlockfile' was not declared in this scope; did you mean 'fallback_file'?
 1646 |     funlockfile(file_);
      |     ^~~~~~~~~~~
      |     fallback_file

Would it be possible to add a define to avoid using lock/unlock/getc_unlocked, so that it can be built on platforms that do not support these functions?

[vitaut]

Just removing these calls might be undesirable. I think we should figure out what printf does on these systems and do something similar.

[vitaut]

Looks like this is what used on Amiga:

https://github.com/bebbo/libnix/blob/152139ecbaa9f1349ceec5944d181d1786a84789/sources/headers/stdio.h#L81

[glebm]

Got a response in the Xbox issue: XboxDev/nxdk#672 (comment)

[jwillikers]

I see these same errors attempting to build for a microcontroller with both newlib and picolibc:

In file included from /home/jordan/.conan2/p/b/fmtc75dbc04c5faa/b/src/src/format.cc:8:
/home/jordan/.conan2/p/b/fmtc75dbc04c5faa/b/src/include/fmt/format-inl.h: In constructor 'fmt::v11::detail::file_print_buffer::file_print_buffer(FILE*)':
/home/jordan/.conan2/p/b/fmtc75dbc04c5faa/b/src/include/fmt/format-inl.h:1638:5: error: 'flockfile' was not declared in this scope; did you mean '_flockfile'?
 1638 |     flockfile(f);
      |     ^~~~~~~~~
      |     _flockfile
/home/jordan/.conan2/p/b/fmtc75dbc04c5faa/b/src/include/fmt/format-inl.h: In destructor 'fmt::v11::detail::file_print_buffer::~file_print_buffer()':
/home/jordan/.conan2/p/b/fmtc75dbc04c5faa/b/src/include/fmt/format-inl.h:1646:5: error: 'funlockfile' was not declared in this scope; did you mean '_funlockfile'?
 1646 |     funlockfile(file_);
      |     ^~~~~~~~~~~
      |     _funlockfile

[xiyoo0812]

Similarly, it is not possible to build on PS4 and PS5

[vitaut]

Added flockfile detection in 486838f. Note that providing flockfile/funlockfile is a better solution especially on platforms targeted by these C library implementations because it prevents dynamic memory allocations in the common case. It also seems trivial to do since they already have the necessary primitives, they just have wrong names, e.g. __STDIO_LOCK instead of flockfile.

[vitaut]

@glebm could you verify that it fixes the problem on Amiga?

[glebm]

@vitaut The build is still failing but now the errors are different

• Amiga: https://github.com/diasurgical/devilutionX/actions/runs/9846219340/job/27183525051?pr=7181
• Xbox: https://github.com/diasurgical/devilutionX/actions/runs/9846219369/job/27183524301?pr=7181

[vitaut]

A more complete fix: 92227c7.

[glebm]

All builds are now green! Thank you for the fix!