Macro code crasher on re-run

[Daniel Jacobowitz <drow@mvista.com>]

There's a bug in default_macro_scope.  I was in the middle of working on
something else when GDB crashed, so I can't fix it now, and Jim probably can
think of a better fix than I can - hence this message :) Or I'll get to it
in a few days.

Here's the problem.  I've just typed "run".

82      struct macro_scope *
83      default_macro_scope (void)
84      {
85        struct symtab_and_line sal;
86        struct macro_source_file *main;
87        struct macro_scope *ms;
88
89        /* If there's a selected frame, use its PC.  */
90        if (deprecated_selected_frame)
91          sal = find_pc_line (get_frame_pc (deprecated_selected_frame), 0);

So deprecated_selected_frame is NULL...

92
93        /* If the target has any registers at all, then use its PC.  Why we
94           would have registers but no stack, I'm not sure.  */
95        else if (target_has_registers)
96          sal = find_pc_line (read_pc (), 0);

And target_has_registers is false.

97
98        /* If all else fails, fall back to the current listing position.  */
99        else
100         {
101           /* Don't call select_source_symtab here.  That can raise an
102              error if symbols aren't loaded, but GDB calls the expression
103              evaluator in all sorts of contexts.
104
105              For example, commands like `set width' call the expression
106              evaluator to evaluate their numeric arguments.  If the
107              current language is C, then that may call this function to
108              choose a scope for macro expansion.  If you don't have any
109              symbol files loaded, then get_current_or_default would raise an
110              error.  But `set width' shouldn't raise an error just because
111              it can't decide which scope to macro-expand its argument in.  */
112           struct symtab_and_line cursal = 
113                             get_current_source_symtab_and_line ();
114           
115           sal.symtab = cursal.symtab;
116           sal.line = cursal.line;
117         }

So we initialize just the symtab and line pointers.
118
119       return sal_macro_scope (sal);
120     }


39        if (! sal.symtab
40            || ! sal.symtab->macro_table)
41          return 0;

Oops, uninitialized memory read.  That else case can't work; Jim, should we
just return 0 from default_macro_scope if the target isn't running, or
is there a function I don't see somewhere to find the macrotab and
initialize the rest of the symtab?  Should it be "sal = cursal"?

-- 
Daniel Jacobowitz
MontaVista Software                         Debian GNU/Linux Developer