internal-error: insert_step_resume_breakpoint_at_sal

[Nick Roberts <nickrob at snap dot net dot nz>]

Following my earlier e-mail (Wed, 24 Nov 2004 16:48:06 +1300):

 > Debugging emacs in CVS with gdb in CVS, I often get an error if I try to step
 > through the program after setting a breakpoint:
 > 
 > To reproduce:
 > 
 > gdb emacs
 > GNU gdb 6.3.50_2004-11-24-cvs
 > ...
 > (gdb) b Fsplit_window    (for example)
 > (gdb) run
 > 
 > `C-x 2' in Emacs
 > 
 > (gdb) n
 > infrun.c:2763: internal-error: insert_step_resume_breakpoint_at_sal: Assertion `step_resume_breakpoint == NULL' failed.
 > A problem internal to GDB has been detected,

infrun.c (in insert_step_resume_breakpoint_at_sal) says:

  /* There should never be more than one step-resume breakpoint per
     thread, so we should never be setting a new
     step_resume_breakpoint when one is already active.  */

However, in this case (and presumably others too) there is more than one
step-resume breakpoint. insert_step_resume_breakpoint_at_sal is called
at infrun.c:1931 and then infrun.c:1949 through handle_inferior_event:

First time:

#0  insert_step_resume_breakpoint_at_sal (sr_sal=
      {symtab = 0x0, section = 0x0, line = 0, pc = 134872212, end = 0}, sr_id=
      {stack_addr = 3221220224, code_addr = 134872206, special_addr = 0, stack_addr_p = 1, code_addr_p = 1, special_addr_p = 0}) at infrun.c:2671
During symbol reading, incomplete CFI data; unspecified registers (e.g., eax) at#1  0x080fbe4f in insert_step_resume_breakpoint_at_frame (return_frame=0x0)
    at infrun.c:2699
#2  0x080fa6c3 in handle_inferior_event (ecs=0xbffff180) at infrun.c:1931
#3  0x080f9cb8 in wait_for_inferior () at infrun.c:974

Second time:

#0  internal_error (file=0x8221657 "infrun.c", line=2668, 
    string=0x81ef7a1 "%s: Assertion `%s' failed.") at utils.c:789
#1  0x080fbdda in insert_step_resume_breakpoint_at_sal (sr_sal=
      {symtab = 0x0, section = 0x0, line = 0, pc = 134872212, end = 0}, sr_id=
      {stack_addr = 3221220224, code_addr = 134872206, special_addr = 0, stack_addr_p = 1, code_addr_p = 1, special_addr_p = 0}) at infrun.c:2672
#2  0x080fbe4f in insert_step_resume_breakpoint_at_frame (return_frame=0x0)
    at infrun.c:2699
#3  0x080fa677 in handle_inferior_event (ecs=0xbffff180) at infrun.c:1949
#4  0x080f9cb8 in wait_for_inferior () at infrun.c:974


Previously GDB just issued a warning, but there never seemed to be any
harm in dropping the old step_resume_breakpoint. How about replacing:

gdb_assert (step_resume_breakpoint == NULL);

in insert_step_resume_breakpoint_at_sal with:

warning
 ("GDB bug: infrun.c (wait_for_inferior): dropping old step_resume breakpoint");

which used to be in check_for_old_step_resume_breakpoint?


Nick