Re: AIX PIC shared library support

Pushed. Thanks!

Peter

On 08/20/2012 12:12 PM, David Edelsohn wrote:
> The GCC -fpic/-fPIC option has evolved to mean code generation for a
> shared library and changes the optimization behavior of the compiler.
> Code for AIX PowerPC always is PIC, but the optimization behavior is
> affecting AIX.
>
> libtool exports all global symbols on AIX while GCC binds_local_p()
> determines that some function calls are local, causing GCC to emit the
> local (non-external) form of function calls, which generates AIX
> linker warnings.
>
> The IBM XL compiler defaults to the equivalent of -fpic.  GCC could
> try to match that, but it requires working around other GCC bootstrap
> problems and continually chasing compatibility.  The other option is
> to assume that developers using GCC to build shared libraries either
> are using libtool or copying FOSS Makefiles designed for GNU/Linux or
> expecting GNU/Linux compatibility.
>
> The following patch starts to implement the latter by adding "-fPIC"
> to the compiler command line options when building objects for a
> shared library.  Because this places control in the hands of the user
> with a command line option and matches GNU/Linux, this seems better
> than playing with defaults and fighting GCC semantics for building
> shared libraries.
>
> Comments?
>
> Thanks, David
>
>          * m4/libtool.m4 (_LT_COMPILER_PIC): Add -fPIC to GCC and GXX for AIX.
>
> diff --git a/m4/libtool.m4 b/m4/libtool.m4
> index a8ecbc3..d0a5577 100644
> --- a/m4/libtool.m4
> +++ b/m4/libtool.m4
> @@ -3874,6 +3874,7 @@ m4_if([$1], [CXX], [
>          # AIX 5 now supports IA64 processor
>          _LT_TAGVAR(lt_prog_compiler_static, $1)='-Bstatic'
>         fi
> +      _LT_TAGVAR(lt_prog_compiler_pic, $1)='-fPIC'
>         ;;
>
>       amigaos*)
> @@ -4191,6 +4192,7 @@ m4_if([$1], [CXX], [
>          # AIX 5 now supports IA64 processor
>          _LT_TAGVAR(lt_prog_compiler_static, $1)='-Bstatic'
>         fi
> +      _LT_TAGVAR(lt_prog_compiler_pic, $1)='-fPIC'
>         ;;
>
>       amigaos*)
>