Re: [PATCH] fix lookup_symbol foobar

[Elena Zannoni <ezannoni at redhat dot com>]

Committed mainline & branch

elena



Elena Zannoni writes:
 > 
 > This is an interesting buglet:
 > 
 > [ezannoni@tomago gdb]$ cat ~/buglet.c
 > int a = 5;
 > int main (void)
 > {
 >   int sum = 0;
 >   printf ("hello\n");
 >   while ( a > 0)
 >   {
 >     sum += a;
 >     a--;
 >   }
 >   printf ("sum is %d\n", sum);
 >   printf ("bye\n");
 >   return 0;
 > }
 > 
 > 
 > [ezannoni@tomago gdb]$ gdb ~/buglet
 > GNU gdb Red Hat Linux (5.3.90-0.20030710.2rh)
 > Copyright 2003 Free Software Foundation, Inc.
 > GDB is free software, covered by the GNU General Public License, and you are
 > welcome to change it and/or distribute copies of it under certain conditions.
 > Type "show copying" to see the conditions.
 > There is absolutely no warranty for GDB.  Type "show warranty" for details.
 > This GDB was configured as "i386-redhat-linux-gnu"...
 > Setting up the environment for debugging gdb.
 > .gdbinit:5: Error in sourced command file:
 > Function "internal_error" not defined.
 > (gdb) l 
 > 1	int a = 5;
 > 2	int main (void)
 > 3	{
 > 4	  int sum = 0;
 > 5	  printf ("hello\n");
 > 6	  while ( a > 0)
 > 7	  {
 > 8	    sum += a;
 > 9	    a--;
 > 10	  }
 > (gdb) p a
 > $1 = 5
 > (gdb) p sum
 > No symbol "sum" in current context.
 > (gdb) ptype a
 > type = int
 > (gdb) ptype sum
 > No symbol "sum" in current context.
 > (gdb) info addr a
 > Symbol "a" is static storage at address 0x80494b4.
 > (gdb) info addr sum
 > Symbol "sum" is a field of the local class variable `this'
 > 
 > Whoops. 
 > 
 > This is because lookup_symbol in address_info() returns null, and also
 > doesn't initialize *is_a_field_of_this to anything.
 > 
 > I suspect a similar situation can happen in any of the callers of
 > lookup_symbol that set the is_a_field_of_this to a non-null value.
 > 
 > David, you are the one that played around with all this, looks ok to
 > you?
 > 
 > elena
 > 
 > 
 > 2003-08-07  Elena Zannoni  <ezannoni@redhat.com>
 > 
 > 	* symtab.c (lookup_symbol_aux): Make sure that is_a_field_of_this
 > 	contains something meaningful at all times.
 > 
 > 
 > 
 > diff -u -p -r1.113 symtab.c
 > --- symtab.c	12 Jun 2003 15:52:08 -0000	1.113
 > +++ symtab.c	7 Aug 2003 15:33:08 -0000
 > @@ -945,6 +945,14 @@ lookup_symbol_aux (const char *name, con
 >  {
 >    struct symbol *sym;
 >  
 > +  /* Make sure we do something sensible with is_a_field_of_this, since
 > +     the callers that set this parameter to some non-null value will
 > +     certainly use it later and expect it to be either 0 or 1.
 > +     If we don't set it, the contents of is_a_field_of_this are
 > +     undefined.  */
 > +  if (is_a_field_of_this != NULL)
 > +    *is_a_field_of_this = 0;
 > +
 >    /* Search specified block and its superiors.  Don't search
 >       STATIC_BLOCK or GLOBAL_BLOCK.  */
 >  
 > @@ -961,7 +969,6 @@ lookup_symbol_aux (const char *name, con
 >      {
 >        struct value *v = current_language->la_value_of_this (0);
 >  
 > -      *is_a_field_of_this = 0;
 >        if (v && check_field (v, name))
 >  	{
 >  	  *is_a_field_of_this = 1;