Re: [rfa:dwarf2] Use frame_unwind_address_in_block

[Andrew Cagney <ac131313 at redhat dot com>]

> Hello,
>
> This, finally, is the tweak to the dwarf2-unwind code, to use the frame's address-in-block, instead of the frame's PC to select the CFI info.  Two test cases stop failing:
>
> 1gdb.base/corefile.exp: backtrace in corefile.exp FAIL PASS 2gdb.base/gdb1250.exp: backtrace from abort KFAIL PASS
>
> Ok for the mainline?
> Ok to pull something equivalent into 6.0 branch?

FYI,

The attached is the equivalent for the branch.

Andrew

2003-07-18  Andrew Cagney  <cagney@redhat.com>

	* dwarf2-frame.h (dwarf2_frame_sniffer): Replace "dwarf2_frame_p".
	* dwarf2-frame.c (dwarf2_frame_sniffer): Replace "dwarf2_frame_p".
	(dwarf2_frame_cache): Use frame_unwind_address_in_block, instead
	of frame_pc_unwind.
	* i386-tdep.c (i386_gdbarch_init): Update.
	* alpha-tdep.c (alpha_dwarf2_init_abi): Update.

Index: alpha-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/alpha-tdep.c,v
retrieving revision 1.116
diff -u -r1.116 alpha-tdep.c
--- alpha-tdep.c	14 Jun 2003 22:35:23 -0000	1.116
+++ alpha-tdep.c	18 Jul 2003 15:12:50 -0000
@@ -1583,7 +1583,7 @@
 void
 alpha_dwarf2_init_abi (struct gdbarch_info info, struct gdbarch *gdbarch)
 {
-  frame_unwind_append_predicate (gdbarch, dwarf2_frame_p);
+  frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);
   frame_base_append_predicate (gdbarch, dwarf2_frame_base_p);
   set_gdbarch_dwarf2_build_frame_info (gdbarch, dwarf2_build_frame_info);
 }
Index: dwarf2-frame.c
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2-frame.c,v
retrieving revision 1.7.4.1
diff -u -r1.7.4.1 dwarf2-frame.c
--- dwarf2-frame.c	11 Jul 2003 16:56:09 -0000	1.7.4.1
+++ dwarf2-frame.c	18 Jul 2003 15:12:51 -0000
@@ -491,15 +491,12 @@
      done for "normal" frames and not for resume-type frames (signal
      handlers, sentinel frames, dummy frames).
 
-     We don't do what GCC's does here (yet).  It's not clear how
-     reliable the method is.  There's also a problem with finding the
-     right FDE; see the comment in dwarf_frame_p.  If dwarf_frame_p
-     selected this frame unwinder because it found the FDE for the
-     next function, using the adjusted return address might not yield
-     a FDE at all.  The problem isn't specific to DWARF CFI; other
-     unwinders loose in similar ways.  Therefore it's probably
-     acceptable to leave things slightly broken for now.  */
-  fs->pc = frame_pc_unwind (next_frame);
+     frame_unwind_address_in_block does just this.
+
+     It's not clear how reliable the method is though - there is the
+     potential for the register state pre-call being different to that
+     on return.  */
+  fs->pc = frame_unwind_address_in_block (next_frame);
 
   /* Find the correct FDE.  */
   fde = dwarf2_frame_find_fde (&fs->pc);
@@ -708,16 +705,13 @@
 };
 
 const struct frame_unwind *
-dwarf2_frame_p (CORE_ADDR pc)
+dwarf2_frame_sniffer (struct frame_info *next_frame)
 {
-  /* The way GDB works, this function can be called with PC just after
-     the last instruction of the function we're supposed to return the
-     unwind methods for.  In that case we won't find the correct FDE;
-     instead we find the FDE for the next function, or we won't find
-     an FDE at all.  There is a possible solution (see the comment in
-     dwarf2_frame_cache), GDB doesn't pass us enough information to
-     implement it.  */
-  if (dwarf2_frame_find_fde (&pc))
+  /* Grab an address that is guarenteed to reside somewhere within the
+     function.  frame_pc_unwind(), for a no-return next function, can
+     end up returning something past the end of this function's body.  */
+  CORE_ADDR block_addr = frame_unwind_address_in_block (next_frame);
+  if (dwarf2_frame_find_fde (&block_addr))
     return &dwarf2_frame_unwind;
 
   return NULL;
Index: dwarf2-frame.h
===================================================================
RCS file: /cvs/src/src/gdb/dwarf2-frame.h,v
retrieving revision 1.1
diff -u -r1.1 dwarf2-frame.h
--- dwarf2-frame.h	31 May 2003 19:18:05 -0000	1.1
+++ dwarf2-frame.h	18 Jul 2003 15:12:51 -0000
@@ -29,7 +29,7 @@
 /* Return the frame unwind methods for the function that contains PC,
    or NULL if it can't be handled by DWARF CFI frame unwinder.  */
 
-const struct frame_unwind *dwarf2_frame_p (CORE_ADDR pc);
+const struct frame_unwind *dwarf2_frame_sniffer (struct frame_info *next_frame);
 
 /* Return the frame base methods for the function that contains PC, or
    NULL if it can't be handled by the DWARF CFI frame unwinder.  */
Index: i386-tdep.c
===================================================================
RCS file: /cvs/src/src/gdb/i386-tdep.c,v
retrieving revision 1.158.2.2
diff -u -r1.158.2.2 i386-tdep.c
--- i386-tdep.c	2 Jul 2003 17:15:54 -0000	1.158.2.2
+++ i386-tdep.c	18 Jul 2003 15:12:52 -0000
@@ -1811,7 +1811,7 @@
   set_gdbarch_fetch_pointer_argument (gdbarch, i386_fetch_pointer_argument);
 
   /* Hook in the DWARF CFI frame unwinder.  */
-  frame_unwind_append_predicate (gdbarch, dwarf2_frame_p);
+  frame_unwind_append_sniffer (gdbarch, dwarf2_frame_sniffer);
   set_gdbarch_dwarf2_build_frame_info (gdbarch, dwarf2_build_frame_info);
 
   frame_base_set_default (gdbarch, &i386_frame_base);