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Re: [RFC] Avoid crash when calling warning too early
- From: Sergio Durigan Junior <sergiodj at redhat dot com>
- To: Tom Tromey <tom at tromey dot com>
- Cc: gdb-patches at sourceware dot org
- Date: Sat, 06 Oct 2018 15:32:12 -0400
- Subject: Re: [RFC] Avoid crash when calling warning too early
- References: <20181006192007.1945-1-tom@tromey.com>
On Saturday, October 06 2018, Tom Tromey wrote:
> I happened to notice that if you pass the name of an existing file
> (not a directory) as the argument to --data-directory, gdb will crash:
>
> $ ./gdb -nx --data-directory ./gdb
> ../../binutils-gdb/gdb/target.c:590:56: runtime error: member call on null pointer of type 'struct target_ops'
>
> This happens because warning ends up calling
> target_supports_terminal_ours, which calls current_top_target, which
> returns nullptr this early.
>
> This fixes the problem by handling this case specially in
> target_supports_terminal_ours.
>
> I wasn't sure whether this warranted a test case, hence the RFC.
Thanks for the patch. I remember stumbling upon this issue a while ago,
and had a similar patch to fix it, but I think I forgot to submit it.
> gdb/ChangeLog
> 2018-10-06 Tom Tromey <tom@tromey.com>
>
> * target.c (target_supports_terminal_ours): Handle case where
> current_top_target returns nullptr.
> ---
> gdb/ChangeLog | 5 +++++
> gdb/target.c | 5 +++++
> 2 files changed, 10 insertions(+)
>
> diff --git a/gdb/target.c b/gdb/target.c
> index 2d98954b54..a261155f29 100644
> --- a/gdb/target.c
> +++ b/gdb/target.c
> @@ -587,6 +587,11 @@ target_terminal::info (const char *arg, int from_tty)
> int
> target_supports_terminal_ours (void)
> {
> + /* This can be called before there is any target, so we must check
> + for nullptr here. */
> + target_ops *top = current_top_target ();
> + if (top == nullptr)
> + return false;
> return current_top_target ()->supports_terminal_ours ();
> }
The patch looks good to me. My only question is about whether we still
require a newline between variable declarations and the rest of the
code. I still follow this rule (because I think it improves code
readability), but now with C++11 I'm not sure if it's still being
enforced.
Thanks,
--
Sergio
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