[FFmpeg-devel] PIC and YASM

[Reimar Döffinger]

On Sun, Nov 08, 2009 at 03:27:16PM +0100, Reimar D?ffinger wrote:
> On Sun, Nov 08, 2009 at 01:47:20PM +0000, M?ns Rullg?rd wrote:
> > Reimar D?ffinger <Reimar.Doeffinger at gmx.de> writes:
> > 
> > > Hello,
> > > I have been trying to figure out some compilation issues with hardened
> > > gentoo on AMD64 and they all come down to YASM.
> > > Several issues:
> > > -DPIC is and must be added explicitly to the yasm flags.
> > > in particular:
> > > --enable-pic will not add -DPIC to YASMFLAGS, nor will the enable_pic
> > > function. --enable-shared will though.
> > 
> > That's easy to fix.  Does this work better?
> 
> Probably, though why not just put it in the enable_pic function?
> (x86inc.asm will unset it by itself where it is not supported)
> I also suspect that my proposal will allow to get rid of that
> "enable pic" hack for OpenBSD and the macho64 special-case.
> Not to mention the Haiku/Zeta case that just looks very strange,
> if not to say wrong (adding -DPIC but not doing enable_pic?).
> However that darwin case means the check would have to be done earlier
> (to get -mdynamic-no-pic):
> Index: configure
> ===================================================================
> --- configure   (revision 20469)
> +++ configure   (working copy)
> @@ -1876,6 +1876,7 @@
>  
>  enable $arch $subarch
>  enabled spic && enable pic
> +check_cpp_condition stdlib.h "defined(__PIC__) || defined(__pic__) || defined(PIC)" && enable pic
>  
>  # OS specific
>  case $target_os in
> @@ -2103,6 +2104,7 @@
>      add_cppflags -DPIC
>      add_cflags   -fPIC
>      add_asflags  -fPIC
> +    append YASMFLAGS "-DPIC"
>  }
>  
>  enabled pic && enable_pic
> @@ -2231,7 +2233,6 @@
>  
>      YASMFLAGS="-f $objformat -DARCH_$(toupper $subarch)"
>      enabled     x86_64        && append YASMFLAGS "-m amd64"
> -    enabled_all x86_64 shared && append YASMFLAGS "-DPIC"
>      case "$objformat" in
>          elf) enabled debug && append YASMFLAGS "-g dwarf2" ;;
>          macho64)              append YASMFLAGS "-DPIC -DPREFIX" ;;

Hmm. I guess I obviously haven't tested it, since the YASMFLAGS= line
will of course overwrite it.
However does anything speak against
> enabled pic && append YASMFLAGS "-DPIC"
instead of
> enabled_all x86_64 shared && append YASMFLAGS "-DPIC"
?