Re: [PATCH 09/29] bisect: libify `check_good_are_ancestors_of_bad` and its dependents

[Johannes Schindelin <Johannes.Schindelin@gmx.de>]

Hi,

On Mon, 20 Jan 2020, Miriam Rubio wrote:

> From: Pranit Bauva <pranit.bauva@gmail.com>
>
> Since we want to get rid of git-bisect.sh it would be necessary to
> convert those exit() calls to return statements so that errors can be
> reported.
>
> Emulate try catch in C by converting `exit(<positive-value>)` to
> `return <negative-value>`. Follow POSIX conventions to return
> <negative-value> to indicate error.
>
> Turn `exit()` to `return` calls in `check_good_are_ancestors_of_bad()`.
>
> Code that turns -11(early success code) to 0 from
> `check_good_are_ancestors_of_bad()` has been moved to
> `cmd_bisect__helper()`.
>
> Handle the return value in dependent function `bisect_next_all()`.
>
> Mentored-by: Christian Couder <chriscool@tuxfamily.org>
> Mentored by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
> Signed-off-by: Pranit Bauva <pranit.bauva@gmail.com>
> Signed-off-by: Tanushree Tumane <tanushreetumane@gmail.com>
> Signed-off-by: Miriam Rubio <mirucam@gmail.com>
> ---
>  bisect.c                 | 42 ++++++++++++++++++++++++++--------------
>  builtin/bisect--helper.c | 12 ++++++++++--
>  2 files changed, 37 insertions(+), 17 deletions(-)
>
> diff --git a/bisect.c b/bisect.c
> index 367258b0dd..2b80597a1d 100644
> --- a/bisect.c
> +++ b/bisect.c
> @@ -865,9 +865,10 @@ static int check_ancestors(struct repository *r, int rev_nr,
>   *
>   * If that's not the case, we need to check the merge bases.
>   * If a merge base must be tested by the user, its source code will be
> - * checked out to be tested by the user and we will exit.
> + * checked out to be tested by the user and we will return.
>   */
> -static void check_good_are_ancestors_of_bad(struct repository *r,
> +
> +static int check_good_are_ancestors_of_bad(struct repository *r,
>  					    const char *prefix,
>  					    int no_checkout)
>  {
> @@ -876,8 +877,15 @@ static void check_good_are_ancestors_of_bad(struct repository *r,
>  	int fd, rev_nr, res = 0;
>  	struct commit **rev;
>
> -	if (!current_bad_oid)
> -		die(_("a %s revision is needed"), term_bad);
> +	/*
> +	 * We don't want to clean the bisection state
> +	 * as we need to get back to where we started
> +	 * by using `git bisect reset`.
> +	 */
> +	if (!current_bad_oid) {
> +		res = error(_("a %s revision is needed"), term_bad);
> +		goto done;
> +	}

Why not just return here? Ah, there is a `filename` that was allocated...
it is too bad that we have a mailing-list based review, as the hunk
context simply cannot be extended in a mail.

Personally, I think it would be nicer to split the definition of
`filename` from its declaration and move it _after_ this conditional code,
so that we can `return` right away.

However, there is a more pressing issue than that: `die()` exits with exit
code 128, so in keeping with the idea to hand down negative exit codes as
return values, should we not assign `res = -128` here?

>
>  	/* Check if file BISECT_ANCESTORS_OK exists. */
>  	if (!stat(filename, &st) && S_ISREG(st.st_mode))
> @@ -893,18 +901,20 @@ static void check_good_are_ancestors_of_bad(struct repository *r,
>  	if (check_ancestors(r, rev_nr, rev, prefix))
>  		res = check_merge_bases(rev_nr, rev, no_checkout);
>  	free(rev);
> -	if(res)
> -		exit(res == -11 ? 0 : -res);
> -
> -	/* Create file BISECT_ANCESTORS_OK. */
> -	fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
> -	if (fd < 0)
> -		warning_errno(_("could not create file '%s'"),
> -			      filename);
> -	else
> -		close(fd);
> +
> +	if (!res)
> +	{

We usually put the `{` on the same line as the `if` condition (like you
did in the `if (!current_bad_oid)` line above.

The rest looks reasonable. Thank you,
Johannes

> +		/* Create file BISECT_ANCESTORS_OK. */
> +		fd = open(filename, O_CREAT | O_TRUNC | O_WRONLY, 0600);
> +		if (fd < 0)
> +			warning_errno(_("could not create file '%s'"),
> +				      filename);
> +		else
> +			close(fd);
> +	}
>   done:
>  	free(filename);
> +	return res;
>  }
>
>  /*
> @@ -975,7 +985,9 @@ int bisect_next_all(struct repository *r, const char *prefix, int no_checkout)
>  	if (read_bisect_refs())
>  		die(_("reading bisect refs failed"));
>
> -	check_good_are_ancestors_of_bad(r, prefix, no_checkout);
> +	res = check_good_are_ancestors_of_bad(r, prefix, no_checkout);
> +	if (res)
> +		return res;
>
>  	bisect_rev_setup(r, &revs, prefix, "%s", "^%s", 1);
>  	revs.limited = 1;
> diff --git a/builtin/bisect--helper.c b/builtin/bisect--helper.c
> index 826fcba2ed..5e0f759d50 100644
> --- a/builtin/bisect--helper.c
> +++ b/builtin/bisect--helper.c
> @@ -666,7 +666,8 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
>
>  	switch (cmdmode) {
>  	case NEXT_ALL:
> -		return bisect_next_all(the_repository, prefix, no_checkout);
> +		res = bisect_next_all(the_repository, prefix, no_checkout);
> +		break;
>  	case WRITE_TERMS:
>  		if (argc != 2)
>  			return error(_("--write-terms requires two arguments"));
> @@ -713,5 +714,12 @@ int cmd_bisect__helper(int argc, const char **argv, const char *prefix)
>  		return error("BUG: unknown subcommand '%d'", cmdmode);
>  	}
>  	free_terms(&terms);
> -	return !!res;
> +	/*
> +	 * Handle early success
> +	 * From check_merge_bases > check_good_are_ancestors_of_bad > bisect_next_all
> +	 */
> +	if (res == -11)
> +		res = 0;
> +
> +	return res < 0 ? -res : res;
>  }
> --
> 2.21.1 (Apple Git-122.3)
>
>