[zig cc] unistd.h doesn't appear to reflect the targeted glibc version

[chouquette]

Zig Version

0.13.0

Steps to Reproduce and Observed Behavior

Hello!
I'm trying to compile utils-linux with zig cc while targeting glibc 2.17.
From what I can see, the glibc library itself is correctly missing symbols added in later versions, however unistd.h does include the prototypes for such functions.
In this case, close_range which was added in 2.34

This leads to compile error as utils-linux attempts to provide a compat function:

In file included from ../disk-utils/fsck.c:59:
../include/fileutils.h:90:19: error: static declaration of 'close_range' follows non-static declaration
   90 | static inline int close_range(unsigned int first, unsigned int last, int flags)
      |                   ^
/snap/zig/11625/lib/libc/include/generic-glibc/unistd.h:1211:12: note: previous declaration is here
 1211 | extern int close_range (unsigned int __fd, unsigned int __max_fd,
      |            ^

The setup can easily be reproduced with git clone --depth=1 https://github.com/util-linux/util-linux.git && cd util-linux && mkdir build-zig && ./autogen.sh && cd build-zig && CC='zig cc --target=x86_64-linux-gnu.2.17' ../configure && make

Expected Behavior

unistd.h doesn't include declaration for functions unavailable in the targeted glibc version

[alexrp]

We unfortunately don't have a good solution for versioning headers at the moment. The current approach is to manually patch them with appropriate checks, e.g. b7a98d0.

[chouquette]

Alright, that seems fair :)

I opened #22771 which solves my use case for now!

Thanks for your very quick response 🙏