Re: [PATCH 3/5] perf tools: Add GCC optimization to memoryallocating functions

[Davidlohr Bueso]

On Fri, 2010-11-26 at 22:30 -0200, Arnaldo Carvalho de Melo wrote:
> Em Fri, Nov 26, 2010 at 07:47:19PM -0200, Arnaldo Carvalho de Melo escreveu:
> > From: Davidlohr Bueso <dave@xxxxxxx>
> > 
> > We can benefit from the alloc_size attribute in xrealloc and zalloc.
> > 
> > Quoting from http://gcc.gnu.org/onlinedocs/gcc/Function-Attributes.html:
> > 
> > "The alloc_size attribute is used to tell the compiler that the function return
> > value points to memory, where the size is given by one or two of the functions
> > parameters. GCC uses this information to improve the correctness of
> > __builtin_object_size."
> 
> Ingo, please don't pull this, it breaks the build with older GCCs...
> 

Sorry about that. This attribute was added for the 4.2 series in early
2007 (http://gcc.gnu.org/ml/gcc-patches/2007-04/msg01649.html)

> util/util.h:185: warning: âalloc_sizeâ attribute directive ignored
> util/util.h:190: warning: âalloc_sizeâ attribute directive ignored
> make: *** [/home/acme/git/build/perf/builtin-annotate.o] Error 1
> make: Leaving directory `/home/acme/git/linux-2.6-tip/tools/perf'
> [acme@mica linux-2.6-tip]$ gcc -v
> Using built-in specs.
> Target: x86_64-redhat-linux
> Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
> --infodir=/usr/share/info --enable-shared --enable-threads=posix
> --enable-checking=release --with-system-zlib --enable-__cxa_atexit
> --disable-libunwind-exceptions --enable-libgcj-multifile
> --enable-languages=c,c++,objc,obj-c++,java,fortran,ada
> --enable-java-awt=gtk --disable-dssi --enable-plugin
> --with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre
> --with-cpu=generic --host=x86_64-redhat-linux
> Thread model: posix
> gcc version 4.1.2 20071124 (Red Hat 4.1.2-42)
> 
> I'll reorg this using compiler.h tricks probably, for now I'll just
> remove it from my perf/core branch.
> 
> - Arnaldo
> 


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