Issue #22311 has been updated by himura467 (Akito Shitara). Using autoconf 2.73 with `AC_CHECK_DECL` as you suggested would fix it. However, requiring 2.73 seems difficult for now, since the release tarballs are generated by 2.71, and Ubuntu 24.04/26.04 ship 2.71/2.72. So I think a runtime check would be more practical, either: 1. using `__builtin_available(macOS 27.0, *)`, or 2. checking the weakly linked symbols, as done for `utimensat` in file.c ([b6b9a619](https://github.com/ruby/ruby/commit/b6b9a6190def53aa53ac816a51034fa1c96ed70b)) and `pthread_threadid_np` in thread_pthread.c ([45177129](https://github.com/ruby/ruby/commit/45177129a75c5bfd03933b82076e8dc49acc500f)). Ref: https://blog.himura467.com/entry/2026/09/14/062404 ---------------------------------------- Bug #22311: Build crashes on macOS 26 with the macOS 27 SDK because pipe2() and dup3() are unavailable https://bugs.ruby-lang.org/issues/22311#change-118993 * Author: himura467 (Akito Shitara) * Status: Open * Backport: 3.3: UNKNOWN, 3.4: UNKNOWN, 4.0: UNKNOWN ---------------------------------------- ## Environment - macOS 26.6.2 - Command Line Tools with MacOSX27.0.sdk (default `MacOSX.sdk`) - Apple clang version 21.0.0 (clang-2100.3.34.2) ## Steps to reproduce ./autogen.sh mkdir build && cd build ../configure make ## Result The build warns about `dup3` and `pipe2`, and then miniruby crashes: ../io.c:389:19: warning: 'dup3' is only available on macOS 27.0 or newer [-Wunguarded-availability-new] ../io.c:432:18: warning: 'pipe2' is only available on macOS 27.0 or newer [-Wunguarded-availability-new] ../io.c:8141:18: warning: 'pipe2' is only available on macOS 27.0 or newer [-Wunguarded-availability-new] ... make: *** [uncommon.mk:1331: builtin_binary.rbbin] Segmentation fault: 11 ## Cause The macOS 27 SDK declares `dup3()` and `pipe2()` as available since macOS 27.0. `AC_CHECK_FUNCS` links them without including headers, so configure defines `HAVE_DUP3` and `HAVE_PIPE2`. In io.c, they are weakly linked through the header and are NULL at runtime on macOS 26. $ nm -m miniruby | grep -E '_(pipe2|dup3) ' (undefined) weak external _dup3 (from libSystem) (undefined) weak external _pipe2 (from libSystem) ## Notes Autoconf 2.73 makes `AC_CHECK_DECL` report "no" for such functions on macOS. https://github.com/autotools-mirror/autoconf/blob/0a51305fff8847edd3e9da9e53... -- https://bugs.ruby-lang.org/