fix: remove -stdlib=libc++ from setup helpers, not needed on modern Pythons (#4639)

* Inject -stdlib=libc++ on macOS only when it's supported, close #4637.

On macOS, by default, pybind11 currently unconditionally set the compiler
flag "-stdlib=libc++" in Pybind11Extension.__init__(), regardless of which
compiler is used. This flag is required for clang, but is invalid for GCC.
If GCC is used, it causes compilation failures in all Python projects that
use pybind11, with the error message:

    arm64-apple-darwin22-gcc: error: unrecognized command-line option -stdlib=libc++.

This commit uses has_flag() to detect whether "-stdlib=libc++" on macOS,
and injects this flag from build_ext.build_extensions(), rather than
setting it unconditionally.

Signed-off-by: Yifeng Li <tomli@tomli.me>

* revert: just remove flags

---------

Signed-off-by: Yifeng Li <tomli@tomli.me>
Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>
This commit is contained in:
biergaizi 2023-05-01 14:14:52 +00:00 committed by GitHub
parent 956390a87f
commit da91926295
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@ -144,7 +144,6 @@ class Pybind11Extension(_Extension): # type: ignore[misc]
self.cxx_std = cxx_std
cflags = []
ldflags = []
if WIN:
cflags += ["/EHsc", "/bigobj"]
else:
@ -154,11 +153,7 @@ class Pybind11Extension(_Extension): # type: ignore[misc]
c_cpp_flags = shlex.split(env_cflags) + shlex.split(env_cppflags)
if not any(opt.startswith("-g") for opt in c_cpp_flags):
cflags += ["-g0"]
if MACOS:
cflags += ["-stdlib=libc++"]
ldflags += ["-stdlib=libc++"]
self._add_cflags(cflags)
self._add_ldflags(ldflags)
@property
def cxx_std(self) -> int: