Python 3.11 is unbuildable with GCC on macOS (error: 'HAVE_MKFIFOAT_RUNTIME' undeclared, error: 'HAVE_MKNODAT_RUNTIME' undeclared)

[biergaizi]

Bug report

Due to missing fallback macro definitions in Modules/posixmodule.c (source) for HAVE_MKFIFOAT_RUNTIME and HAVE_MKNODAT_RUNTIME, Python 3.11 cannot be built with GCC on macOS, due to the following failures:

./Modules/posixmodule.c: In function 'parse_posix_spawn_flags':
./Modules/posixmodule.c:186:64: warning: comparison between pointer and integer
  186 |                                 (posix_spawn != NULL && setsid != NULL)
      |                                                                ^~
./Modules/posixmodule.c:6026:13: note: in expansion of macro 'HAVE_POSIX_SPAWN_SETSID_RUNTIME'
 6026 |         if (HAVE_POSIX_SPAWN_SETSID_RUNTIME) {
      |             ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
./Modules/posixmodule.c: In function 'os_mkfifo_impl':
./Modules/posixmodule.c:10690:17: error: 'HAVE_MKFIFOAT_RUNTIME' undeclared (first use in this function); did you mean 'HAVE_MKDIRAT_RUNTIME'?
10690 |             if (HAVE_MKFIFOAT_RUNTIME) {
      |                 ^~~~~~~~~~~~~~~~~~~~~
      |                 HAVE_MKDIRAT_RUNTIME
./Modules/posixmodule.c:10690:17: note: each undeclared identifier is reported only once for each function it appears in
./Modules/posixmodule.c: In function 'os_mknod_impl':
./Modules/posixmodule.c:10759:17: error: 'HAVE_MKNODAT_RUNTIME' undeclared (first use in this function); did you mean 'HAVE_MKDIRAT_RUNTIME'?
10759 |             if (HAVE_MKNODAT_RUNTIME) {
      |                 ^~~~~~~~~~~~~~~~~~~~
      |                 HAVE_MKDIRAT_RUNTIME
./Modules/posixmodule.c: In function 'probe_mkfifoat':
arm64-apple-darwin22-gcc  -Wsign-compare -DNDEBUG     -O2 -pipe -fwrapv -std=c11 -Wextra -Wno-unused-parameter -Wno-missing-field-initializers -Wstrict-prototypes -Werror=implicit-function-declaration -fvisibility=hidden  -I./Include/internal  -I. -I./Include -I/Users/gentoo/gentoo/tmp/usr/include/ncursesw   -DPy_BUILD_CORE_BUILTIN -c ./Modules/_codecsmodule.c -o Modules/_codecsmodule.o
./Modules/posixmodule.c:15647:23: error: 'HAVE_MKFIFOAT_RUNTIME' undeclared (first use in this function); did you mean 'HAVE_MKDIRAT_RUNTIME'?
15647 | PROBE(probe_mkfifoat, HAVE_MKFIFOAT_RUNTIME)
      |                       ^~~~~~~~~~~~~~~~~~~~~
./Modules/posixmodule.c:15611:11: note: in definition of macro 'PROBE'
15611 |       if (test) {        \
      |           ^~~~
./Modules/posixmodule.c: In function 'probe_mknodat':
./Modules/posixmodule.c:15651:22: error: 'HAVE_MKNODAT_RUNTIME' undeclared (first use in this function); did you mean 'HAVE_MKDIRAT_RUNTIME'?
15651 | PROBE(probe_mknodat, HAVE_MKNODAT_RUNTIME)
      |                      ^~~~~~~~~~~~~~~~~~~~
./Modules/posixmodule.c:15611:11: note: in definition of macro 'PROBE'
15611 |       if (test) {        \
      |           ^~~~
make: *** [Makefile:2695: Modules/posixmodule.o] Error 1
make: *** Waiting for unfinished jobs....

In Modules/posixmodule.c, Python conditionally defines a series of macros that indicate whether a system call is supported based on #ifdef checks. By default, the clang specific __builtin_available() compiler built-in function is used to check them. But if __builtin_available() is unavailable, a fallback is also provided.

For example, for HAVE_FSTATAT_RUNTIME, we have:

#ifdef HAVE_BUILTIN_AVAILABLE
#  define HAVE_FSTATAT_RUNTIME __builtin_available(macOS 10.10, iOS 8.0, *)
// [...]

#else /* Xcode 8 or earlier */

   /* __builtin_available is not present in these compilers, but
    * some of the symbols might be weak linked (10.10 SDK or later
    * deploying on 10.9.
    *
    * Fall back to the older style of availability checking for
    * symbols introduced in macOS 10.10.
    */

#  ifdef HAVE_FSTATAT
#    define HAVE_FSTATAT_RUNTIME (fstatat != NULL)
#  endif

#endif

The fallback is important because it's not only used to support older Xcode or macOS, but it also provides fallback when GCC is used. The function __builtin_available() is clang-only and does not exist in GCC. In the past, this was handled by the else portion of the ifdef, so it worked on GCC as well. Unfortunately, when HAVE_MKFIFOAT_RUNTIME and HAVE_MKDIRAT_RUNTIME have been added to the code, a fallback was never provided, thus, compiling Python 3.11 with GCC now fails due to undeclared macros.

Your environment

• CPython versions tested on: Python 3.11.3
• Operating system and architecture: macOS 13.2.1
• GCC 12.2.0

Linked PRs

• gh-104106: Add gcc fallback of mkfifoat/mknodat for macOS #104129
• [3.11] gh-104106: Add gcc fallback of mkfifoat/mknodat for macOS (gh-104129) #104187

[corona10]

@biergaizi Can you please check that #104129 solve your issue?

--- a/Modules/posixmodule.c
+++ b/Modules/posixmodule.c
@@ -175,6 +175,14 @@
 #    define HAVE_PWRITEV_RUNTIME (pwritev != NULL)
 #  endif
 
+#  ifdef HAVE_MKFIFOAT
+#    define HAVE_MKFIFOAT_RUNTIME (mkfifoat != NULL)
+#  endif
+
+#  ifdef HAVE_MKNODAT
+#    define HAVE_MKNODAT_RUNTIME (mknodat != NULL)
+#  endif
+
 #endif
 
 #ifdef HAVE_FUTIMESAT

[biergaizi]

No, because this patch contains a typo. #ifdef HAVE_MKNODAT_RUNTIME should be #ifdef HAVE_MKNODAT

[corona10]

@biergaizi Thanks, I updated the diff, is the changes solve your issue?

[biergaizi]

Yes, the revised patch works, posixmodule.c now passes build without failures.

[corona10]

@biergaizi Thank you for the report!