Re: musl segfaulting when compiled with -O2

[Rich Felker <dalias@libc.org>]

On Tue, Mar 07, 2017 at 05:32:35PM -0300, Breno Leitao wrote:
> Musl package on Debian on ppc64le is broken.
> 
> When running any software with it, it segfaults. Doing a little bit of
> debugging I found that libc.so is broken.
> 
> I got the upstream code, and found that the problme is also
> reproducible.
> 
> I found that the problem only happen when compiling with -O2 and -O3. If
> I compile musl with -O1 or -O0, the problm does not happen.
> 
> This is the bt of the code that crashes:
> 
> (gdb) bt
> #0  0x0000000148b84dc0 in ?? ()
> #1  0x0000000048bdb8dc in _dlstart_c (sp=0x3fffc33294b0, dynv=<optimized out>) at ldso/dlstart.c:147
> #2  0x0000000048bdebe0 in _dlstart ()
> 
> (gdb) up
> #1  0x0000000048bdb8dc in _dlstart_c (sp=0x3fffc33294b0, dynv=<optimized out>) at ldso/dlstart.c:147
> 147		dls2((void *)base, sp);
> 
> $ gcc --version
> gcc (Debian 6.3.0-5) 6.3.0 20170124
> 
> Not sure if this is a GCC issue or a musl issue now.

Can you post the crashing libc.so somewhere? Depending on how they're
building it, the problem could be in various different places. A
glibc-targeted powerpc* gcc is not suitable for compiling musl, since
it has various ABI mismatches, but that's probably not what you're
seeing here even if one was used.

Rich