Re: [rfa:dwarf2] Use frame_unwind_address_in_block

[Elena Zannoni <ezannoni at redhat dot com>]

Andrew Cagney writes:
 > 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?

seems sane.

elena

 > 
 > Andrew
 > 2003-07-16  Andrew Cagney  <cagney@redhat.com>
 > 
 > 	* dwarf2-frame.c (dwarf2_frame_sniffer): Use
 > 	frame_unwind_address_in_block, instead of frame_pc_unwind.
 > 	(dwarf2_frame_cache): Ditto.
 > 
 > Index: dwarf2-frame.c
 > ===================================================================
 > RCS file: /cvs/src/src/gdb/dwarf2-frame.c,v
 > retrieving revision 1.9
 > diff -u -r1.9 dwarf2-frame.c
 > --- dwarf2-frame.c	16 Jul 2003 22:29:13 -0000	1.9
 > +++ dwarf2-frame.c	16 Jul 2003 23:13:29 -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);
 > @@ -710,15 +707,11 @@
 >  const struct frame_unwind *
 >  dwarf2_frame_sniffer (struct frame_info *next_frame)
 >  {
 > -  CORE_ADDR pc = frame_pc_unwind (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;