[Bug libstdc++/55394] Using call_once without -lpthread compiles without warning

[trippels at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=55394

Markus Trippelsdorf <trippels at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2016-11-19
                 CC|                            |trippels at gcc dot gnu.org
     Ever confirmed|0                           |1

--- Comment #4 from Markus Trippelsdorf <trippels at gcc dot gnu.org> ---
clang's libc++.so.1 avoids the issue because it is linked with libpthread.so.0:

 % ldd /usr/lib/libc++.so.1
        linux-vdso.so.1 (0x00007ffc1618f000)
        libpthread.so.0 => /lib/libpthread.so.0 (0x00007fe0f4fd7000)
        libc.so.6 => /lib/libc.so.6 (0x00007fe0f4c3a000)
        libm.so.6 => /lib/libm.so.6 (0x00007fe0f499f000)
        librt.so.1 => /lib/librt.so.1 (0x00007fe0f4797000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x00007fe0f477e000)
        /lib64/ld-linux-x86-64.so.2 (0x00005575a195e000)

libstc++ isn't:

 % ldd /usr/lib/gcc/x86_64-pc-linux-gnu/7.0.0/libstdc++.so.6
        linux-vdso.so.1 (0x00007ffd14540000)
        libm.so.6 => /lib/libm.so.6 (0x00007f73bec87000)
        libc.so.6 => /lib/libc.so.6 (0x00007f73be8ea000)
        /lib64/ld-linux-x86-64.so.2 (0x00005594a5a06000)
        libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x00007f73be8d1000)