This is the mail archive of the gdb-patches@sources.redhat.com mailing list for the GDB project.


Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]
Other format: [Raw text]

Add frame_is_callee_p(), use in dwarf2-frame.c?


Hello,

Following up the comment:

/* Unwind the PC.

     Note that if NEXT_FRAME is never supposed to return (i.e. a call
     to abort), the compiler might optimize away the instruction at
     NEXT_FRAME's return address.  As a result the return address will
     point at some random instruction, and the CFI for that
     instruction is probably wortless to us.  GCC's unwinder solves
     this problem by substracting 1 from the return address to get an
     address in the middle of a presumed call instruction (or the
     instruction in the associated delay slot).  This should only be
     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);


Given MichaelC's flurry of bugs on this, should the fix be added to 6?

As for the dwarf2_frame_p test, outch! Any ideas? Change the parameter to ``address_in_block'', instead of a PC?

Regardless, for a ``normal frame'' test, I'd like to suggest ``frame_is_callee_p()'' as something suitable descriptive. Thoughts?

Andrew





Index Nav: [Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav: [Date Prev] [Date Next] [Thread Prev] [Thread Next]