gcc-devel does not build on Sonoma: error: call to undeclared function 'dup2'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]

[barracuda156]

/usr/bin/clang -arch arm64 -c -DHAVE_CONFIG_H -pipe -Os -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk -I/opt/local/include -isysroot/Library/Developer/CommandLineTools/SDKs/MacOSX14.sdk -I. -I/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc-devel/libgcc-devel/work/gcc-14-20240303/libiberty/../include  -W -Wall -Wwrite-strings -Wc++-compat -Wstrict-prototypes -Wshadow=local -pedantic  -D_GNU_SOURCE  /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc-devel/libgcc-devel/work/gcc-14-20240303/libiberty/fibheap.c -o fibheap.o
yes
checking whether /usr/bin/clang -arch arm64 supports -Wold-style-definition... /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc-devel/libgcc-devel/work/gcc-14-20240303/libiberty/filedescriptor.c:45:10: error: call to undeclared function 'dup2'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
  return dup2 (fd, fd) < 0;
         ^
1 warning and 1 error generated.
make[3]: *** [filedescriptor.o] Error 1
make[3]: *** Waiting for unfinished jobs....
warning: unknown warning option '-Wshadow=local' [-Wunknown-warning-option]
1 warning generated.
yes
checking whether /usr/bin/clang -arch arm64 supports -Wc++-compat... 1 warning generated.
make[3]: Leaving directory `/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc-devel/libgcc-devel/work/build/build-arm64-apple-darwin23/libiberty'
make[2]: *** [all-build-libiberty] Error 2

Same error with the latest snapshot of gcc14:

opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_gcc-devel/libgcc-devel/work/gcc-14-20240324/libiberty/filedescriptor.c:45:10: error: call to undeclared function 'dup2'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
  return dup2 (fd, fd) < 0;
         ^
1 warning and 1 error generated.
make[3]: *** [filedescriptor.o] Error 1
make[3]: *** Waiting for unfinished jobs....
1 warning generated.

[ryandesign (Ryan Carsten Schmidt)]

​POSIX says dup2 is in <unistd.h> but I don't see that header included by libiberty/filedescriptor.c. You could try adding that #include and see if it solves the problem. It looks like this code was ​moved to filedescriptor.c from another file 4.5 years ago, and that other file did include <unistd.h>. In any case, it's probably an upstream problem that needs to be reported the developers of gcc.

[ryandesign (Ryan Carsten Schmidt)]

In addition, the problem may be that the earlier #elif defined(F_GETFD) path isn't being taken. On my macOS 12 SDK I see F_GETFD is defined in <fcntl.h> which filedescriptor.c does include but only if HAVE_FCNTL_H is defined. Maybe there is a bug in the configure script test and HAVE_FCNTL_H isn't getting defined; check your config.log.