Partial fix for PR backtrace/1718.

* i386-tdep.c (i386_analyze_frame_setup): Handle more instructions
that GCC migrates into the prolugue.  Don't handle any
instructions that clobber %ebx.

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index cbe7bdc..26c6c84 100644 (file)
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,3 +1,10 @@
+2004-07-24  Mark Kettenis  <kettenis@gnu.org>
+
+       Partial fix for PR backtrace/1718.
+       * i386-tdep.c (i386_analyze_frame_setup): Handle more instructions
+       that GCC migrates into the prolugue.  Don't handle any
+       instructions that clobber %ebx.
+
 2004-07-23  Andrew Cagney  <cagney@gnu.org>
 
        Use regcache_raw_collect instead of regcache_collect.

diff --git a/gdb/i386-tdep.c b/gdb/i386-tdep.c
index 19e7ed9..d51e162 100644 (file)
--- a/gdb/i386-tdep.c
+++ b/gdb/i386-tdep.c
@@ -503,20 +503,28 @@ i386_analyze_frame_setup (CORE_ADDR pc, CORE_ADDR current_pc,
 
       op = read_memory_unsigned_integer (pc + 1, 1);
 
-      /* Check for some special instructions that might be migrated
-        by GCC into the prologue.  We check for
+      /* Check for some special instructions that might be migrated by
+        GCC into the prologue.  At this point in the prologue, code
+        should only touch the scratch registers %eax, %ecx and %edx,
+        so we check for
 
-           xorl %ebx, %ebx
+           movl $XXX, %eax
+           movl $XXX, %ecx
+           movl $XXX, %edx
+
+        These instructions have opcodes 0xb8, 0xb9 and 0xba.
+
+        We also check for
+
+           xorl %eax, %eax
            xorl %ecx, %ecx
            xorl %edx, %edx
-           xorl %eax, %eax
 
         and the equivalent
 
-           subl %ebx, %ebx
+           subl %eax, %eax
            subl %ecx, %ecx
            subl %edx, %edx
-           subl %eax, %eax
 
         Because of the symmetry, there are actually two ways to
         encode these instructions; with opcode bytes 0x29 and 0x2b
@@ -524,20 +532,34 @@ i386_analyze_frame_setup (CORE_ADDR pc, CORE_ADDR current_pc,
 
         Make sure we only skip these instructions if we later see the
         `movl %esp, %ebp' that actually sets up the frame.  */
-      while (op == 0x29 || op == 0x2b || op == 0x31 || op == 0x33)
+      while ((op >= 0xb8 && op <= 0xba)
+            || op == 0x29 || op == 0x2b
+            || op == 0x31 || op == 0x33)
        {
-         op = read_memory_unsigned_integer (pc + skip + 2, 1);
-         switch (op)
+         if (op >= 0xb8 && op <= 0xba)
            {
-           case 0xdb:  /* %ebx */
-           case 0xc9:  /* %ecx */
-           case 0xd2:  /* %edx */
-           case 0xc0:  /* %eax */
-             skip += 2;
-             break;
-           default:
-             return pc + 1;
+             /* Skip the `movl' instructions cited above.  */
+             skip += 5;
            }
+         else
+           {
+             /* Skip the `subl' and `xorl' instructions cited above.  */
+             op = read_memory_unsigned_integer (pc + skip + 2, 1);
+             switch (op)
+               {
+               case 0xc0:      /* %eax */
+               case 0xc9:      /* %ecx */
+               case 0xd2:      /* %edx */
+                 skip += 2;
+                 break;
+               default:
+                 return pc + 1;
+               }
+           }
+
+         /* If that's all, return now.  */
+         if (current_pc <= pc + skip + 1)
+           return current_pc;
 
          op = read_memory_unsigned_integer (pc + skip + 1, 1);
        }