Re: [PATCH v2 02/11] bisect--helper: introduce new `write_in_file()` function

[Junio C Hamano <gitster@pobox.com>]

Miriam Rubio <mirucam@gmail.com> writes:

> Let's refactor code adding a new `write_in_file()` function
> that opens a file for writing a message and closes it.
>
> This helper will be used in later steps and makes the code
> simpler and easier to understand.
>
> Mentored-by: Christian Couder <chriscool@tuxfamily.org>
> Mentored-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
> Signed-off-by: Miriam Rubio <mirucam@gmail.com>
> ---
>  builtin/bisect--helper.c | 27 +++++++++++++++++++++------
>  1 file changed, 21 insertions(+), 6 deletions(-)
>
> diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
> index 1f81cff1d8..e949ea74e2 100644
> --- a/builtin/bisect--helper.c
> +++ b/builtin/bisect--helper.c
> @@ -74,6 +74,26 @@ static int one_of(const char *term, ...)
>  	return res;
>  }
>  
> +static int write_in_file(const char *filepath, const char *mode, const char *format,...)
> +{
> +	FILE *fp = NULL;

It is crystal clear in this concise helper function that fp will
never be used without getting assigned the returned value from
fopen(), so I do not think there is any need to initialize it to
NULL.

I'd use "path", not "filepath" (which I do not think we use anywhere
in our codebase), if I were writing this function, by the way.

> +	va_list args;
> +	int res = 0;
> +
> +	if (!strcmp(mode, "a") && !strcmp(mode, "w"))
> +		return error_errno(_("wrong writing mode '%s'"), mode);

I do not see where you saw a failure from a call to system library
function, which would make 'errno' variable valid at this point, so
I am puzzled.  By using error_errno(), whose error status are you
trying to show?

Puzzled.  Shouldn't it be just error(_("..."), mode)?

> +	fp = fopen(filepath, mode);
> +	if (!fp)
> +		return error_errno(_("could not open file '%s'"), filepath);

This one would show why fopen() failed, so error_errno() would be good.
Does it help us help the users if they can tell us which mode we failed
to write to the file?   Something like

	cannot open file '%s' in mode '%s'

perhaps?

> +	va_start(args, format);
> +	res = vfprintf(fp, format, args);
> +	va_end(args);
> +	if (!res)
> +		return error_errno(_("could not write to file '%s'"), filepath);

This would show errors from vfprintf(), which is good.  However, you
fail to fclose the FILE when this return is hit, which is not good.

> +	return fclose(fp);
> +}
> +
>  static int check_term_format(const char *term, const char *orig_term)
>  {
>  	int res;
> @@ -104,7 +124,6 @@ static int check_term_format(const char *term, const char *orig_term)
>  
>  static int write_terms(const char *bad, const char *good)
>  {
> -	FILE *fp = NULL;
>  	int res;
>  
>  	if (!strcmp(bad, good))
> @@ -113,12 +132,8 @@ static int write_terms(const char *bad, const char *good)
>  	if (check_term_format(bad, "bad") || check_term_format(good, "good"))
>  		return -1;
>  
> -	fp = fopen(git_path_bisect_terms(), "w");
> -	if (!fp)
> -		return error_errno(_("could not open the file BISECT_TERMS"));
> +	res = write_in_file(git_path_bisect_terms(), "w", "%s\n%s\n", bad, good);
>  
> -	res = fprintf(fp, "%s\n%s\n", bad, good);
> -	res |= fclose(fp);
>  	return (res < 0) ? -1 : 0;
>  }