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Re: [PATCH] gdb: trivial segfault fix in tui
On Tue, Aug 14, 2012 at 4:03 PM, Hal Ashburner <hal@ashburner.info> wrote:
> Dear Hafiz,
>
> Thank you for letting me know this.
> I've added a ChangeLog entry to the patch. I hope this is done the correct way.
>
> By way of trivia, I fixed this bug because I hit it more than once.
>
>
> diff --git a/gdb/ChangeLog b/gdb/ChangeLog
> index 81c03ee..e1a080f 100644
> --- a/gdb/ChangeLog
> +++ b/gdb/ChangeLog
> @@ -1,3 +1,7 @@
> +2012-08-15 Hal Ashburner <hal@ashburner.info>
> +
> + * tui/tui-source.c: Check for null pointer to prevent segfault.
> +
> 2012-08-10 Sergio Durigan Junior <sergiodj@redhat.com>
>
> * linespec.c (find_methods): Remove unused variables `i1' and
> diff --git a/gdb/tui/tui-source.c b/gdb/tui/tui-source.c
> index 9ba9b1d..0c94aed 100644
> --- a/gdb/tui/tui-source.c
> +++ b/gdb/tui/tui-source.c
> @@ -334,11 +334,13 @@ tui_show_symtab_source (struct gdbarch *gdbarch,
> struct symtab *s,
> int
> tui_source_is_displayed (char *fname)
> {
> - return (TUI_SRC_WIN->generic.content_in_use
> - && (filename_cmp (((struct tui_win_element *)
> - (tui_locator_win_info_ptr ())->
> - content[0])->which_element.locator.file_name,
> - fname) == 0));
> + if (tui_locator_win_info_ptr()->content)
> + return (TUI_SRC_WIN->generic.content_in_use
> + && (filename_cmp (((struct tui_win_element *)
> + (tui_locator_win_info_ptr ())->
> + content[0])->which_element.locator.file_name,
> + fname) == 0));
> + return 0;
> }
It seems tui is quite fragile with respect to window resizes.
I was able to get a segv here for similar reasons, but I didn't write
down the steps I did to trigger it. :-(
tui-source.c:
element->which_element.source.is_exec_point =
(filename_cmp (((struct tui_win_element *)
locator->content[0])->which_element.locator.file_name,
s->filename) == 0
tui is also a bit, umm, weird.
tui_free_window has this:
generic_win = tui_locator_win_info_ptr ();
if (generic_win != (struct tui_gen_win_info *) NULL)
{
tui_delete_win (generic_win->handle);
generic_win->handle = (WINDOW *) NULL;
}
but tui_locator_win_info_ptr will never return NULL.
struct tui_gen_win_info *
tui_locator_win_info_ptr (void)
{
return &_locator;
}
Blech!
In the end I suspect there's a better fix, but I don't know tui well enough.
I'd wait to see if someone else does.
Also, I'd add a comment explaining *why* the test for content != NULL,
and I'd rewrite it as:
return (TUI_SRC_WIN->generic.content_in_use
&& tui_locator_win_info_ptr()->content != NULL
&& ...);
The style is more consistent this way.