Re: [PATCH v2] diff: ensure correct lifetime of external_diff_cmd

> According to getenv(3)'s notes:
>
>     The implementation of getenv() is not required to be reentrant.  The
>     string pointed to by the return value of getenv() may be statically
>     allocated, and can be modified by a subsequent call to getenv(),
>     putenv(3), setenv(3), or unsetenv(3).
> ...
> Signed-off-by: Kim Gybels <kgybels@infogroep.be>
> ---

>
> Uses xstrdup_or_null as suggested by Eric Sunshine.
>
>  diff.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/diff.c b/diff.c
> index dc9965e836..5634992bbc 100644
> --- a/diff.c
> +++ b/diff.c
> @@ -487,11 +487,11 @@ static const char *external_diff(void)
>  	static const char *external_diff_cmd = NULL;
>  	static int done_preparing = 0;
>  
>  	if (done_preparing)
>  		return external_diff_cmd;
> -	external_diff_cmd = getenv("GIT_EXTERNAL_DIFF");
> +	external_diff_cmd = xstrdup_or_null(getenv("GIT_EXTERNAL_DIFF"));
>  	if (!external_diff_cmd)
>  		external_diff_cmd = external_diff_cmd_cfg;
>  	done_preparing = 1;
>  	return external_diff_cmd;
>  }