Re: [PATCH] help: Fix size passed to qsort

From: Junio C Hamano <gitster@pobox.com>
Date: Sep 18, 2014, 17:17 UTC
Message-ID: <xmqq8ulgq25h.fsf@gitster.dls.corp.google.com>
In-Reply-To: <1410956079-23513-1-git-send-email-stefanbeller@gmail.com>

Stefan Beller <stefanbeller@gmail.com> writes:

> We actually want to have the size of one 'name' and not the size
> of the names array.

I suspect that the latter is "size of a pointer that points at a cmdname structure", but the original code in help_unknown_cmd() is wrong. The ones in load_command_list() do this correctly and another qsort() invocation in this function does so as well. I wonder why they didn't correctly cut&paste ;-)

746c221a (git wrapper: also use aliases to correct mistyped commands, 2008-09-10) seemed to have introduced the culprit.

The call to uniq() would fail to uniquify because main_cmds would have the standard command all in front and then aliases and commands in the user's PATH later, but I do not quite see if there is any end-user observable breakages that can arise from this. What is the practical implication of this breakage?

No, I am not saying we do not have to fix it; I am just being curious why this patch does not show the existing breakage with a new test.

Thanks.

Show 19 quoted lines

>
> Signed-off-by: Stefan Beller <stefanbeller@gmail.com>
> ---
>  help.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/help.c b/help.c
> index 7af65e2..2072a87 100644
> --- a/help.c
> +++ b/help.c
> @@ -305,7 +305,7 @@ const char *help_unknown_cmd(const char *cmd)
>  	add_cmd_list(&main_cmds, &aliases);
>  	add_cmd_list(&main_cmds, &other_cmds);
>  	qsort(main_cmds.names, main_cmds.cnt,
> -	      sizeof(main_cmds.names), cmdname_compare);
> +	      sizeof(*main_cmds.names), cmdname_compare);
>  	uniq(&main_cmds);
>  
>  	/* This abuses cmdname->len for levenshtein distance */