Re: [PATCH 1/3] Fix segfault when unwinding JIT frames using a custom reader.

[Jan Kratochvil <jan dot kratochvil at redhat dot com>]

On Sun, 04 Nov 2012 18:03:49 +0100, Sanjoy Das wrote:
> Issue http://sourceware.org/bugzilla/show_bug.cgi?id=14550
[...]
> --- a/gdb/jit.c
> +++ b/gdb/jit.c
> @@ -724,8 +724,18 @@ finalize_symtab (struct gdb_symtab *stab, struct objfile *objfile)
>         gdb_block_iter = gdb_block_iter->next)
>      {
>        if (gdb_block_iter->parent != NULL)
> -        BLOCK_SUPERBLOCK (gdb_block_iter->real_block) =
> -          gdb_block_iter->parent->real_block;
> +	{
> +	  /* If the plugin specifically mentioned a parent block, we
> +	     use that.  */
> +	  BLOCK_SUPERBLOCK (gdb_block_iter->real_block) =
> +	    gdb_block_iter->parent->real_block;
> +	}
> +      else
> +	{
> +	  /* And if not, we set a default parent block.  */
> +	  BLOCK_SUPERBLOCK (gdb_block_iter->real_block) =
> +	    BLOCKVECTOR_BLOCK (symtab->blockvector, STATIC_BLOCK);
> +	}

While I find this patch correct:

(1) The interface for JIT readers was AFAIK designed to be easier than what
    GDB provides internally.  Therefore I think gdb_block->parent should not
    exist, it can be rebuilt from gdb_block->begin and gdb_block->end,
    together with some assumption about gdb_block->next ordering.

(2) Otherwise to keep it ABI compatible one should at least sanity check and
    error if gdb_block->begin and gdb_block->end do not match the ordering via
    gdb_block->parent.



Thanks,
Jan