Re: Simple but crucial bug fix to gdb

[Jim Blandy <jimb at zwingli dot cygnus dot com>]

Charlie Mills <cmills@synopsys.com> writes:
> Bug description:  gdb 4.xx and 5.0 crashes while reading our executable.
> Our executable is the result of linking objects compiled by gcc with
> other objects compiled using SPARCworks CC.  The stack trace is
> appended at the end of this message.

I managed to construct an executable that would crash GDB in the same
way yours did (by editing a binary to get stabs of the sort Sun's
compiler produces).  I'm committing the patch below, which prevents
the crashes.  It's essentially the same fix as yours, except that
there are two cases (static and global functions) that need attention,
not one.

I'm concerned that your builds are producing debugging entries for
functions that appear to be outside of any compilation unit.  GDB
doesn't really know what to do with this; at the moment, it mostly
ignores the function's entry.  I wish I could play around with the
situation and figure out what really needs to be done; with the
current fix, I strongly suspect that GDB will be unable to find
debugging information for some functions in some circumstances.  So
that the problem doesn't disappear from view entirely, my patch makes
GDB complain (that's a technical term) when it sees debugging info
like that present in your executable.  Perhaps we'll find another
case, and we'll be able to really fix the bug.

In any case, thanks for the bug report.

2001-06-01  Jim Blandy  <jimb@redhat.com>

	* partial-stab.h: New complaint: function_outside_compilation_unit.
	(case N_FUN: case 'f':, case N_FUN: case 'F':): If pst is zero,
	complain, and don't try to set pst's start address.

Index: gdb/partial-stab.h
===================================================================
RCS file: /cvs/src/src/gdb/partial-stab.h,v
retrieving revision 1.9
diff -c -r1.9 partial-stab.h
*** gdb/partial-stab.h	2001/05/31 03:41:31	1.9
--- gdb/partial-stab.h	2001/06/01 20:24:26
***************
*** 40,45 ****
--- 40,48 ----
  
  switch (CUR_SYMBOL_TYPE)
    {
+     static struct complaint function_outside_compilation_unit = {
+       "function `%s' appears to be defined outside of all compilation units", 0, 0
+     };
      char *p;
      /*
       * Standard, external, non-debugger, symbols
***************
*** 576,581 ****
--- 579,592 ----
  	continue;
  
        case 'f':
+         if (! pst)
+           {
+             int name_len = p - namestring;
+             char *name = xmalloc (name_len + 1);
+             memcpy (name, namestring, name_len);
+             name[name_len] = '\0';
+             complain (&function_outside_compilation_unit, name);
+           }
  	CUR_SYMBOL_VALUE += ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
  #ifdef DBXREAD_ONLY
  	/* Kludges for ELF/STABS with Sun ACC */
***************
*** 600,609 ****
  	   the bounds created by N_SO symbols.  If that's the case
  	   use the address of this function as the low bound for
  	   the partial symbol table.  */
! 	if (textlow_not_set
! 	    || (pst && CUR_SYMBOL_VALUE < pst->textlow
! 		&& CUR_SYMBOL_VALUE
! 		!= ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile))))
  	  {
  	    pst->textlow = CUR_SYMBOL_VALUE;
  	    textlow_not_set = 0;
--- 611,622 ----
  	   the bounds created by N_SO symbols.  If that's the case
  	   use the address of this function as the low bound for
  	   the partial symbol table.  */
! 	if (pst
!             && (textlow_not_set
!                 || (CUR_SYMBOL_VALUE < pst->textlow
!                     && (CUR_SYMBOL_VALUE
!                         != ANOFFSET (objfile->section_offsets,
!                                      SECT_OFF_TEXT (objfile))))))
  	  {
  	    pst->textlow = CUR_SYMBOL_VALUE;
  	    textlow_not_set = 0;
***************
*** 620,625 ****
--- 633,646 ----
  	   are put into the global psymtab like one would expect.
  	   They're also in the minimal symbol table.  */
        case 'F':
+         if (! pst)
+           {
+             int name_len = p - namestring;
+             char *name = xmalloc (name_len + 1);
+             memcpy (name, namestring, name_len);
+             name[name_len] = '\0';
+             complain (&function_outside_compilation_unit, name);
+           }
  	CUR_SYMBOL_VALUE += ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile));
  #ifdef DBXREAD_ONLY
  	/* Kludges for ELF/STABS with Sun ACC */
***************
*** 647,656 ****
  	   the bounds created by N_SO symbols.  If that's the case
  	   use the address of this function as the low bound for
  	   the partial symbol table.  */
! 	if (textlow_not_set
! 	    || (pst && CUR_SYMBOL_VALUE < pst->textlow
! 		&& CUR_SYMBOL_VALUE
! 		!= ANOFFSET (objfile->section_offsets, SECT_OFF_TEXT (objfile))))
  	  {
  	    pst->textlow = CUR_SYMBOL_VALUE;
  	    textlow_not_set = 0;
--- 668,679 ----
  	   the bounds created by N_SO symbols.  If that's the case
  	   use the address of this function as the low bound for
  	   the partial symbol table.  */
! 	if (pst
!             && (textlow_not_set
!                 || (CUR_SYMBOL_VALUE < pst->textlow
!                     && (CUR_SYMBOL_VALUE
!                         != ANOFFSET (objfile->section_offsets,
!                                      SECT_OFF_TEXT (objfile))))))
  	  {
  	    pst->textlow = CUR_SYMBOL_VALUE;
  	    textlow_not_set = 0;