Re: [PATCH] Small segfault fix when there is no python

Sergio Durigan Junior
2014-03-20T17:31:28Z

On Thursday, March 20 2014, Daniel Gutson wrote:

> Hi,
>
> the small attached patch prevents gdb to segfault when an extension
> language definition has no ops,
> which e.g. occurs when HAVE_PYTHON is not defined so
> extension_language_python remains with ops in NULL.
> This causes the line
> if (extlang->ops->eval_from_control_command != NULL)
> (in eval_ext_lang_from_control_command) to dereference a null pointer.

Hi Daniel,

Thanks for the patch. This is a simple patch so it doesn't need a
copyright assignment from you. However, if you intend to continue
contributing to GDB, please e-mail me offlist and I can send you the
papers to obtain the assignment.

Just a few comments about formatting issues.

> 2014-03-20 Daniel Gutson (daniel.gutson@tallertechnologies.com)
>
> gdb/
> * extension.c: (eval_ext_lang_from_control_command) Added check to
> prevent dereference of null pointer.

The ChangeLog format is wrong. Take a look at the ChangeLog file for
lots of examples, but basically you need to write:

2014-03-20 Your Name <your@email>

* file.c (function): Added check to prevent blabla...

Pay attention to the 2 spaces between the date, the name and the e-mail,
and also to the TAB character indenting the description.

> diff --git a/gdb/extension.c b/gdb/extension.c
> index c2f502b..8357ee8 100644
> --- a/gdb/extension.c
> +++ b/gdb/extension.c
> @@ -342,11 +342,14 @@ eval_ext_lang_from_control_command (struct command_line *cmd)
> {
> if (extlang->cli_control_type == cmd->control_type)
> {
> - if (extlang->ops->eval_from_control_command != NULL)
> - {
> - extlang->ops->eval_from_control_command (extlang, cmd);
> - return;
> - }
> + if (extlang->ops != NULL)
> + {
> + if (extlang->ops->eval_from_control_command != NULL)
> + {
> + extlang->ops->eval_from_control_command (extlang, cmd);
> + return;
> + }
> + }

You could simplify this by writing:

if (extlang->ops != NULL && extlang->ops->eval_from_control_command != NULL)

If you don't want to join the two "if"s, then you don't need to put the
braces on the outter "if", because it has one single statement.

The patch looks good to me, but I'm not a maintainer and can't approve
it.

Thanks,

--
Sergio