Re: [RFC/RFA] target.c: Check current_target in target_resize_to_sections

[Andrew Cagney <cagney@gnu.org>]

> (with instances of gdbserver running on both ports on the remotehost).
> 
> The errors I see are:
> gdb in realloc(): warning: modified (page-) pointer
> ../../../gdb-w/gdb/utils.c:994: internal-error: virtual memory exhausted: can't allocate 2032 bytes
> 
> (the former error is from the NetBSD realloc call)
> 
> The problem is that update_current_inferior() will copy a valid
> to_sections value out of one of the targets in the stack into
> current_target, but that pointer may become invalid later when
> target_resize_to_sections() is called again on any target using the
> same pointer. Finally, when handle_inferior_event() calls
> SOLIB_ADD(.., &current_target, ...), target_resize_to_sections() calls
> realloc() again on a pointer that's already been realloc'd. "Boom."
> 
> My fix is to make target_resize_to_sections update current_target as
> well as all of the targets in target_structs. Seems to do the job,
> though I can't say it thrills me.
> 
> Comments? Suggestions for better approaches? It definitely fixes the
> problem, and doesn't seem any messier than the rest of the target
> stack stuff. It might be better to not use current_target with
> anything that looks at to_sections, but I've no idea how difficult it
> might be to do that.
> 
>         - Nathan
> 
> 2004-08-25  Nathan J. Williams  <nathanw@wasabisystems.com>
> 
> 	* target.c (target_resize_to_sections): Check
> 	current_target.to_sections for an old value when updating.

Can you just add some sort of brief comment noting why current_target 
also needs to be checked.  With that it's ok (but post the revised patch 
when committing).

Long term `current_target', along with this problem, will go away.

Andrew


> Index: target.c
> ===================================================================
> RCS file: /cvs/src/src/gdb/target.c,v
> retrieving revision 1.78
> diff -u -r1.78 target.c
> --- target.c	3 Aug 2004 00:57:26 -0000	1.78
> +++ target.c	25 Aug 2004 20:35:37 -0000
> @@ -1415,6 +1415,11 @@
>  	      (*t)->to_sections_end = target->to_sections_end;
>  	    }
>  	}
> +      if (current_target.to_sections == old_value)
> +	{
> +	  current_target.to_sections = target->to_sections;
> +	  current_target.to_sections_end = target->to_sections_end;
> +	}
>      }
>    
>    return old_count;
> 
>