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

[Iain Sandoe <developer at sandoe-acoustics dot co dot uk>]

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?
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)