Segfault if printing constructor..

[David Lecomber <david at lecomber dot net>]

With the simple program here, gdb 6.3 or gdb 6.4, and current CVS, g++
4.0.2 (fedora 4 x86), we can get a segfault every time with a simple
three liner:

break 'X::f'
run 
print X



class X
{
 public:
  X();  // standard constructor
  void f();
};

int main(int argc, char **argv)
{
  X x;
  x.f();
  return 1;
}


X::X()
{
}

void X::f()
{
}



gcc 3.2.2 code does not produce the problem, but perhaps a bit of
resilience could be added to GDB to cope nicely.  Essentially, inside
value_fn_field, the lookup_symbol call finds the class, not the
constructor, and we get a segfault as sym->ginfo->value->block is null
here:



struct value*
value_fn_field (struct value **arg1p, struct fn_field *f, int j, struct
type *type,
		int offset)
{

[ snip ]

  v = allocate_value (ftype);
  if (sym)
    {
      VALUE_ADDRESS (v) = BLOCK_START (SYMBOL_BLOCK_VALUE (sym));
    }
  else
[ snip ] 

It's been a while since I submitted/completed a patch here.  It'd be
relatively easy to add simple checks to stop the segfault (ie. check for
null, do something else).  But, would that be the right method or just a
pointless patch? 




-- 
David Lecomber <david@lecomber.net>