Re: failure of pructl (atexit/_Block_copy/--no-allow-shlib-undefined)

On Wed, Dec 1, 2021 at 8:05 PM John-Mark Gurney <jmg@funkthat.com> wrote:
>
> Hello,
>
> It seems like the recent changes to make --no-allow-shlib-undefined
> broke pructl.
>
> lib/libc/stdlib/atexit.c uses a weak _Block_copy symbol, but
> pructl does not use atexit_b, and yet gets the following error:
> : && /usr/bin/cc -Werror -O2 -pipe  -fstack-protector-strong -isystem /usr/local/include -fno-strict-aliasing -std=c99 -fstack-protector-strong CMakeFiles/pructl.dir/pructl.c.o -o pructl  -Wl,-rpath,/usr/local/lib:  /usr/local/lib/libpru.so && :
> ld: error: /lib/libc.so.7: undefined reference to _Block_copy [--no-allow-shlib-undefined]
> cc: error: linker command failed with exit code 1 (use -v to see invocation)
>
> What is the correct fix?  It seems like atexit.c or the linker should
> be fixed, as pructl doesn't use atexit_b at all.
>

CC dim@ and jrtc27@... this seems like a toolchain regression? We're
relying on the address of weak _Block_copy to simply evaluate to NULL
if it's undefined here, which seems legit and pretty well-defined at
this point from my recollection.