pthread is always linked to the binary with zig cc #20919
Description
Zig Version
0.14.0-dev.829+2e26cf83c
Steps to Reproduce and Observed Behavior
Given this helloworld.c file:
#include <stdio.h>
#include <stdlib.h>
int main()
{
puts("hello world");
system("/bin/ls"); // <-- Maybe this trigger zig to link to pthread
return 0;
}Build it with zig cc
> zig cc -target x86_64-linux-gnu -g ./helloworld.c
> ldd a.out
linux-vdso.so.1 (0x000078a750191000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x000078a750173000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x000078a74fe00000)
/lib64/ld-linux-x86-64.so.2 (0x000078a750193000)
> rm a.out
> zig cc -target x86_64-linux-gnu -no-pthread -g ./helloworld.c
zig: warning: argument unused during compilation: '-no-pthread' [-Wunused-command-line-argument]
> ldd a.out
linux-vdso.so.1 (0x000079cd50baf000)
libpthread.so.0 => /lib/x86_64-linux-gnu/libpthread.so.0 (0x000079cd50b91000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x000079cd50800000)
/lib64/ld-linux-x86-64.so.2 (0x000079cd50bb1000)
> rm a.out
> /bin/clang -target x86_64-linux-gnu -g ./helloworld.c
> ldd a.out
linux-vdso.so.1 (0x0000751aa49ff000)
libc.so.6 => /lib/x86_64-linux-gnu/libc.so.6 (0x0000751aa4600000)
/lib64/ld-linux-x86-64.so.2 (0x0000751aa4a01000)libpthread is always linked to the binary by zig, even with -no-pthread option.
Expected Behavior
No pthread is linked in this case maybe.
Context
I'm trying to build a .c file with glibc 2.25 or lower.
If the binary linked with pthread. I cannot run it locally due to this error:
relocation error: ./a.out: symbol system, version GLIBC_2.2.5 not defined in file libpthread.so.0 with link time reference
So for the temporary solution, I viewed ouput of zig cc -v and manually run ld.lld without libpthread.o.