Use of deprecated function `readdir_r` on MacOS

[jll63]

While compiling OpenMethod in CI for MacOS, using the boost-ci reusable workflow, I get:

[...]
2026-04-21T12:55:25.1862560Z Image: macos-26-arm64
2026-04-21T12:55:25.1863520Z Version: 20260413.0345.1
[...]
2026-04-21T12:58:41.9431590Z clang-darwin.compile.c++ bin.v2/libs/filesystem/build/clang-darwin-20/debug/arm_64/cxxstd-17-iso/threading-multi/visibility-hidden/directory.o
2026-04-21T12:58:41.9533840Z /Users/runner/work/openmethod/boost-root/libs/filesystem/src/directory.cpp:354:14: error: 'readdir_r' is deprecated: This function cannot be used safely as it does not take into account the variability of {NAME_MAX}.  It is highly recommended that you use readdir(3) instead. [-Werror,-Wdeprecated-declarations]
2026-04-21T12:58:41.9635680Z   354 |     return ::readdir_r
2026-04-21T12:58:41.9737190Z       |              ^
2026-04-21T12:58:41.9838990Z /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/dirent.h:114:1: note: 'readdir_r' has been explicitly marked deprecated here
2026-04-21T12:58:41.9940910Z   114 | __deprecated_msg("This function cannot be used safely as it does not take into account the variability of {NAME_MAX}.  It is highly recommended that you use readdir(3) instead.")
2026-04-21T12:58:42.0042310Z       | ^
2026-04-21T12:58:42.0142990Z /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/sys/cdefs.h:227:48: note: expanded from macro '__deprecated_msg'
2026-04-21T12:58:42.0243920Z   227 |         #define __deprecated_msg(_msg) __attribute__((__deprecated__(_msg)))
2026-04-21T12:58:42.0345230Z       |                                                       ^
2026-04-21T12:58:42.0447160Z 1 error generated.

[Lastique]

Strangely, I don't see this in my CI, and this warning is supposed to be enabled by default. Do you specify some build flags to make these warnings appear?

I could not find a definitive answer on whether it is thread-safe to use readdir on Mac OS, and since which version, so I'm hesitant to whitelist it in Boost.Filesystem.

[jll63]

Here is the full log. In the meantime, I disabled warnings when building Filesystem as a dependency. Not easy for me to investigate as I am macophobic and I don't have a Mac setup.