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Re: Latest GCC fails to build glibc


On Fri, 15 May 2015, Ondřej Bílka wrote:

> On Thu, May 14, 2015 at 01:59:16PM -0700, Steve Ellcey  wrote:
> > A recent change to GCC (Fix to PR middle-end/66110) has caused glibc to
> > fail to build.  When compiling the latest glibc with the latest GCC I
> > get the error below.  I don't know if this is a GCC problem or a glibc
> > problem.  I notice that when Richard checked this in he also added the
> > use of -Wno-strict-aliasing to the compilation of one of the GCC files.
> > Maybe we need the same thing when compiling memstream.c?
> > 
> Its glibc one. since we added -Werror these issues come from time to
> time when gcc improves/adds warning detection.
> 
> Typically you add pragma to disable these.

Looks like a genuine bug in glibc though - what is the type of 
new_f->fp._sf._sbf?  You are accessing it as struct _IO_FILE_plus.
Eventually the fix is to make _sfb a union.

And yes, I didn't fix the genuine bug in dfp.c either...

Richard.

> 
> 
> > Steve Ellcey
> > sellcey@imgtec.com
> > 
> > 
> > In file included from memstream.c:18:0:
> > memstream.c: In function 'open_memstream':
> > memstream.c:92:22: error: dereferencing type-punned pointer will break strict-aliasing rules [-Werror=strict-aliasing]
> >    _IO_JUMPS ((struct _IO_FILE_plus *) &new_f->fp._sf._sbf) = &_IO_mem_jumps;
> >                       ^
> > libioP.h:107:26: note: in definition of macro '_IO_JUMPS'
> >  #define _IO_JUMPS(THIS) (THIS)->vtable
> >                           ^
> > cc1: all warnings being treated as errors
> > make[2]: *** [/scratch/sellcey/repos/test_deja/obj-mips-mti-linux-gnu/glibc/obj_default/libio/memstream.o] Error 1
> > 
> > Steve Ellcey
> > sellcey@imgtec.com
> 
> 

-- 
Richard Biener <rguenther@suse.de>
SUSE LINUX GmbH, GF: Felix Imendoerffer, Jane Smithard, Dilip Upmanyu, Graham Norton, HRB 21284 (AG Nuernberg)

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