[CentOS-devel] __gthrw___pthread_key_create in devtoolset-6


dacav at teknik.io
Tue May 22 13:04:08 UTC 2018

On 2018-05-22, dacav <dacav at teknik.io> wrote:
> Then of course it gets problematic upon linking time
>     objs/intel-debug/src/logd-main.o:(.rodata+0x8): undefined reference to `__gthrw___pthread_key_create(unsigned int*, void (*)(void*))'
>     collect2: error: ld returned 1 exit status

With a colleague we did some further investigation… and I had
some additional understanding.

I could verify that the missing symbol is generated by an header
file which belongs to the compiler:

    warning: 'int __gthrw___pthread_key_create(pthread_key_t*, void (*)(void*)) throw ()' used but never defined
    BUILDSTDERR:  __gthrw2(__gthrw_(__pthread_key_create),

The current CentOS libc, and specifically libpthread.so, does not
provide such symbol: it is not reported in `objdump --syms`.

For what I understand, devtoolset is providing static linkage for
the functionalities which are not available in the "regular"
CentOS libc. That's the role of libstdc++_nonshared.a according
to [this stackoverflow post][1]. So I also went for
`objdump --syms /opt/rh/devtoolset-6/.../libstd++_nonshared.a`. I
found nothing.

So, in short it would seem like I'm not linking against some
important object code. This object file might be in the standard
CentOS, but more likely in some devtoolset package. The weird
part is that `-pthread` should be (in my opinion) take care of
all this for me.

At this point I'm somewhat out of bullets :) If someone has some
suggestion I will appreciate it. And of course I apologize for
the spam.

[1]: https://stackoverflow.com/questions/15599714/risks-of-different-gcc-versions-at-link-run-time#15602073

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