[Gc] trouble with gc-7.2d compiling against musl libc

[John Spencer]

Hi Ivan,

On 01/06/2013 11:30 AM, Ivan Maidanski wrote:

> Use -DNO_SIGCONTEXT_H instead (I've added this macro recognition to master branch for now).
> I don't know whether we still need inclusion of sigcontext.h for any target.
>

thanks, i will try.

>
> If you provide me with the target test macros, I'll include definitions of NO_SIGCONTEXT_H, NO_PTHREAD_GETATTR_NP, NO_GETCONTEXT,... to gcconfig.h

musl deliberately does not define any __musl__ or similar macros.
read the author's reasoning here:
http://openwall.com/lists/musl/2012/06/18/8

basically, any hardcoded assumption about which platform has which 
functionality is broken by design. a function just needs to be added or 
removed, and your built-in assumption is invalidated.
testing for the availability of such things is exactly what configure is 
for.

> which algorithm is used for detection of main stack base in your case? which macro is defined - STACKBOTTOM, HEURISTIC1, LINUX_STACKBOTTOM?

out of these 3, only LINUX_STACKBOTTOM seems to be defined (i added 
#warnings into os_dep.c in order to find out)

>> i suspect the fallback code when pthread_getattr_np fails is just buggy.
>> afaics this code is only there to find the stack address of the main
>> thread. in that case i wonder why not simply /proc/pid/maps is used
>> instead of using non-portable constructs ?
> As I've said, /proc/pid/maps is a hack (it will not work for non-Linux targets or in sandboxes like valgrind) but it is ok to use this approach for particular targets (no other way).

yes, i assumed this will be used as a fallback when pthread_getattr_np 
fails.

>> in any case, i'd welcome advice on how to workaround this issue, so that
>> i get a working libgc.so in order to use inkscape.
> Thanks for reporting the problem, I'll definitely fix the gc source if we understand how to do it correctly. (Typically, first I apply the fixes to master branch and, then, cherry-pick to 7.2 release.)

thank you. is there anything else i can help with in order to get this 
fixed ?

btw, there are ready to boot qemu/vbox images available on 
http://mirror.wzff.de/sabotage in case you want to try "live" (they come 
with the full set of development tools).

>
> Regards,
> Ivan
>
>>
>>
>> best regards,
>> --JS
>>
>> [1]  https://github.com/rofl0r/sabotage
>> [2]  http://www.musl-libc.org