Re: [Patch gas/mach-o] Generate relocs for local subtractions.

[Tristan Gingold <gingold at adacore dot com>]

On Feb 18, 2012, at 12:40 PM, Iain Sandoe wrote:

> For mach-o, we must generate relocs, even for local subtractions - since we don't know (in general) until later whether the two symbols are going to be in the same sub-section.
> 
> OK?

Yes,

thanks!

> Iain
> 
> gas:
> 	* config/obj-macho.c (obj_mach_o_is_frame_section): New.
> 	(obj_mach_o_allow_local_subtract): New.
> 	* config/obj-macho.h (md_allow_local_subtract): Define.
> 	(obj_mach_o_allow_local_subtract): Declare.
> 
> --- gas/config/obj-macho.c	2012-02-12 15:42:47.000000000 +0000
> +++ gas/config/obj-macho-a.c	2012-02-18 11:30:56.000000000 +0000
> @@ -1483,6 +1483,19 @@
>   return 0;
> }
> 
> +/* Relocation rules are different in frame sections.  */
> +
> +static int
> +obj_mach_o_is_frame_section (segT sec)
> +{
> +  int l;
> +  l = strlen (segment_name (sec));
> +  if ((l == 9 && strncmp (".eh_frame", segment_name (sec), 9) == 0)
> +       || (l == 12 && strncmp (".debug_frame", segment_name (sec), 12) == 0))
> +    return 1;
> +  return 0;
> +}
> +
> /* Zerofill and GB Zerofill sections must be sorted to follow all other
>    sections in their segments.
> 
> @@ -1745,3 +1758,21 @@
>   /* It's a debug symbol.  */
>   s->symbol.flags |= BSF_DEBUGGING;
> }
> +
> +/* Unless we're in a frame section, we need to force relocs to be generated for
> +   local subtractions.  We might eliminate them later (if they are within the
> +   same sub-section) but we don't know that at the point that this decision is
> +   being made.  */
> +
> +int
> +obj_mach_o_allow_local_subtract (expressionS * left ATTRIBUTE_UNUSED,
> +				 expressionS * right ATTRIBUTE_UNUSED,
> +				 segT seg)
> +{
> +  /* Don't interfere if it's one of the GAS internal sections.  */
> +  if (! SEG_NORMAL (seg))
> +    return 1;
> +
> +  /* Allow in frame sections, otherwise emit a reloc.  */
> +  return obj_mach_o_is_frame_section (seg);
> +}
> --- gas/config/obj-macho.h	2012-01-13 15:14:10.000000000 +0000
> +++ gas/config/obj-macho-a.h	2012-02-18 11:33:38.000000000 +0000
> @@ -73,6 +73,12 @@
> #define SET_SECTION_RELOCS(sec, relocs, n) \
>   obj_mach_o_reorder_section_relocs (sec, relocs, n)
> 
> +/* Emit relocs for local subtracts, to cater for subsections-via-symbols.  */
> +#define md_allow_local_subtract(LEFT, RIGHT, SECTION) \
> + obj_mach_o_allow_local_subtract (LEFT, RIGHT, SECTION)
> +extern int obj_mach_o_allow_local_subtract (expressionS *, expressionS *,
> +					    segT);
> +
> #define EMIT_SECTION_SYMBOLS		0
> 
> #define OBJ_PROCESS_STAB(SEG,W,S,T,O,D)	obj_mach_o_process_stab(W,S,T,O,D)
>