Re: [PATCHv2 1/2] builtin/commit.c: drop use snprintf via dynamic allocation

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Elia Pinto <gitter.spiros@xxxxxxxxx> writes:

> In general snprintf is bad because it may silently truncate results if we're
> wrong. In this patch where we use PATH_MAX, we'd want to handle larger
> paths anyway, so we switch to dynamic allocation.
>
> Helped-by: Jeff King <peff@xxxxxxxx>
> Signed-off-by: Elia Pinto <gitter.spiros@xxxxxxxxx>
> ---
> This is the second version of the patch.
>
> I have split the original commit in two, as discussed here
> http://public-inbox.org/git/20161213132717.42965-1-gitter.spiros@xxxxxxxxx/.

And both halves have the same title?

I think the the primary value of this one is that it removes the
PATH_MAX limitation from the environment setting that points to a
filename.  Reducing the number of snprintf() call is a side effect,
even though that may have been what motivated you originally.  The
original code used snprintf() correctly after all.

The primary value of 2/2 is reduction of the cognitive burden from
the programmers---switching to xstrfmt(), they no longer have to
count bytes needed for static allocation.  Reducing the number of
snprintf() call is a side effect, even though that may have been
what motivated you originally.  The original code used snprintf()
correctly after all.

The code looks correct in both patches (except that in 1/2 _clear()
immediately before exit() wouldn't have to be there, but it does not
hurt to have one either).  They need to be better explained.

Thanks.

>  builtin/commit.c | 22 +++++++++++-----------
>  1 file changed, 11 insertions(+), 11 deletions(-)
>
> diff --git a/builtin/commit.c b/builtin/commit.c
> index 0ed634b26..09bcc0f13 100644
> --- a/builtin/commit.c
> +++ b/builtin/commit.c
> @@ -960,15 +960,16 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
>  		return 0;
>  
>  	if (use_editor) {
> -		char index[PATH_MAX];
> -		const char *env[2] = { NULL };
> -		env[0] =  index;
> -		snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", index_file);
> -		if (launch_editor(git_path_commit_editmsg(), NULL, env)) {
> +		struct argv_array env = ARGV_ARRAY_INIT;
> +
> +		argv_array_pushf(&env, "GIT_INDEX_FILE=%s", index_file);
> +		if (launch_editor(git_path_commit_editmsg(), NULL, env.argv)) {
>  			fprintf(stderr,
>  			_("Please supply the message using either -m or -F option.\n"));
> +			argv_array_clear(&env);
>  			exit(1);
>  		}
> +		argv_array_clear(&env);
>  	}
>  
>  	if (!no_verify &&
> @@ -1557,23 +1558,22 @@ static int run_rewrite_hook(const unsigned char *oldsha1,
>  
>  int run_commit_hook(int editor_is_used, const char *index_file, const char *name, ...)
>  {
> -	const char *hook_env[3] =  { NULL };
> -	char index[PATH_MAX];
> +	struct argv_array hook_env = ARGV_ARRAY_INIT;
>  	va_list args;
>  	int ret;
>  
> -	snprintf(index, sizeof(index), "GIT_INDEX_FILE=%s", index_file);
> -	hook_env[0] = index;
> +	argv_array_pushf(&hook_env, "GIT_INDEX_FILE=%s", index_file);
>  
>  	/*
>  	 * Let the hook know that no editor will be launched.
>  	 */
>  	if (!editor_is_used)
> -		hook_env[1] = "GIT_EDITOR=:";
> +		argv_array_push(&hook_env, "GIT_EDITOR=:");
>  
>  	va_start(args, name);
> -	ret = run_hook_ve(hook_env, name, args);
> +	ret = run_hook_ve(hook_env.argv,name, args);
>  	va_end(args);
> +	argv_array_clear(&hook_env);
>  
>  	return ret;
>  }



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