Index: gdb/symtab.c
===================================================================
RCS file: /cvs/src/src/gdb/symtab.c,v
retrieving revision 1.283
diff -u -p -r1.283 symtab.c
--- gdb/symtab.c	21 Jul 2011 15:13:29 -0000	1.283
+++ gdb/symtab.c	25 Oct 2011 17:28:46 -0000
@@ -2474,6 +2474,7 @@ skip_prologue_sal (struct symtab_and_lin
   struct gdbarch *gdbarch;
   struct block *b, *function_block;
   int force_skip, skip;
+  const struct symtab_and_line start_sal_orig = *sal;
 
   /* Do not change the SAL is PC was specified explicitly.  */
   if (sal->explicit_pc)
@@ -2627,6 +2628,29 @@ skip_prologue_sal (struct symtab_and_lin
       sal->line = SYMBOL_LINE (BLOCK_FUNCTION (function_block));
       sal->symtab = SYMBOL_SYMTAB (BLOCK_FUNCTION (function_block));
     }
+  else
+    {
+      /* Check if line number of apparent prologue end comes after
+	 the next line information.  If so, do not skip prologue
+	 as something odd has happened.  Probably gcc bug 49906.
+	 Instead of giving awkward location for the function start,
+	 give the previous good line (fuction start). */
+      const struct symtab_and_line prologue_sal_next
+	= find_pc_line (sal->end, 0);
+
+      if ((sym? (BLOCK_START (SYMBOL_BLOCK_VALUE (sym)) <= prologue_sal_next.end
+		&& prologue_sal_next.end < BLOCK_END (SYMBOL_BLOCK_VALUE (sym)))
+	  : (lookup_minimal_symbol_by_pc_section (prologue_sal_next.end,
+						  section)
+	     == lookup_minimal_symbol_by_pc_section (sal->pc, section)))
+	  && prologue_sal_next.line != 0
+	  && prologue_sal_next.symtab == sal->symtab
+	  && prologue_sal_next.line >= start_sal_orig.line
+	  && prologue_sal_next.line < sal->line)
+	{
+	  *sal = start_sal_orig;
+	}
+    }
 }
 
 /* If P is of the form "operator[ \t]+..." where `...' is
@@ -4432,7 +4456,24 @@ skip_prologue_using_sal (struct gdbarch 
 	  /* Assume that a consecutive SAL for the same (or larger)
 	     line mark the prologue -> body transition.  */
 	  if (sal.line >= prologue_sal.line)
-	    break;
+	    {
+	      /* If the sal following SAL has line number lower than
+		 SAL.LINE, then something is fishy.
+		 Possibly gcc bug 49906  */
+	      const struct symtab_and_line prologue_sal_next
+		= find_pc_line (sal.end, 0);
+
+	      if (prologue_sal_next.end < end_pc
+		  && prologue_sal_next.line != 0
+		  && prologue_sal_next.symtab == sal.symtab
+		  && prologue_sal_next.line >= prologue_sal.line
+		  && prologue_sal_next.line < sal.line)
+		  /* Fishy: we have something past prologue that appears
+		     in the source as before.  Be conservative and return
+		     start of the prologue.  That's the best guess anyway. */
+		prologue_sal.end = prologue_sal.pc;
+	      break;
+	    }
 
 	  /* The line number is smaller.  Check that it's from the
 	     same function, not something inlined.  If it's inlined,