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[patch/rfc,6.1?] Use right frame ID in step_over_function
- From: Andrew Cagney <cagney at gnu dot org>
- To: gdb-patches at sources dot redhat dot com
- Date: Sat, 28 Feb 2004 23:33:51 -0500
- Subject: [patch/rfc,6.1?] Use right frame ID in step_over_function
Hello,
This goes into the "how did it ever work" category. The idea of
step_over_function is that it:
- finds the caller's resume address
- finds the caller's frame ID
and then sets a breakpoint for that caller instance of the function.
The current code:
- finds the caller's resume address
- finds the _callee_ frame ID
and then uses that to set the breakpoint. Now that is plain weird! It
only works because either:
- the step_frame_id patches up the bug
- the values match as GDB is using the inner-most, rather than
outer-most frame address as part of the frame ID
The bug apepars when trying to step over nested shared library non-debug
info functions (making sense?).
I'll follow this up after 6.1 branch is in place.
Its pretty heavy a change to apply to that branch and this late.
However, like Joel's related patch, I suspect it will be needed :-/
Andrew
PS: Why do I have this feeling of dejavu?
* infrun.c (step_over_function): When non-legacy code, and no
step_frame_id, use the unwinder to get the caller's frame ID.
Index: infrun.c
===================================================================
RCS file: /cvs/src/src/gdb/infrun.c,v
retrieving revision 1.137
diff -u -r1.137 infrun.c
--- infrun.c 16 Feb 2004 20:49:51 -0000 1.137
+++ infrun.c 29 Feb 2004 04:10:59 -0000
@@ -2930,6 +2930,7 @@
step_over_function (struct execution_control_state *ecs)
{
struct symtab_and_line sr_sal;
+ struct frame_id sr_id;
init_sal (&sr_sal); /* initialize to zeros */
@@ -2973,13 +2974,29 @@
sr_sal.section = find_pc_overlay (sr_sal.pc);
check_for_old_step_resume_breakpoint ();
- step_resume_breakpoint =
- set_momentary_breakpoint (sr_sal, get_frame_id (get_current_frame ()),
- bp_step_resume);
if (frame_id_p (step_frame_id)
&& !IN_SOLIB_DYNSYM_RESOLVE_CODE (sr_sal.pc))
- step_resume_breakpoint->frame_id = step_frame_id;
+ /* NOTE: cagney/2004-02-27: Use the global state's idea of the
+ stepping frame ID. I suspect this is done as it is lighter
+ weight than a call to get_prev_frame. */
+ sr_id = step_frame_id;
+ else if (legacy_frame_p (current_gdbarch))
+ /* NOTE: cagney/2004-02-27: This is the way it was 'cos this is
+ the way it always was. It should be using the unwound (or
+ caller's) ID, and not this (or the callee's) ID. It appeared
+ to work because: legacy architectures used the wrong end of the
+ frame for the ID.stack (inner-most rather than outer-most) so
+ that the callee's id.stack (un adjusted) matched the caller's
+ id.stack giving the "correct" id; more often than not
+ !IN_SOLIB_DYNSYM_RESOLVE_CODE and hence the code above (it was
+ originally later in the function) fixed the ID by using global
+ state. */
+ sr_id = get_frame_id (get_current_frame ());
+ else
+ sr_id = get_frame_id (get_prev_frame (get_current_frame ()));
+
+ step_resume_breakpoint = set_momentary_breakpoint (sr_sal, sr_id, bp_step_resume);
if (breakpoints_inserted)
insert_breakpoints ();