Re: [PATCH 08/29] bisect: libify `check_merge_bases` and its dependents

> 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_merge_bases()`.
>
> In `check_merge_bases()` there is an early success special case,
> so we have introduced special error code `-11` which indicates early
> success. This `-11` is converted back to `0` in `check_good_are_ancestors_of_bad()`.
>
> Handle the return value in dependent function `check_good_are_ancestors_of_bad()`.

>
> 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 | 21 ++++++++++++++++-----
>  1 file changed, 16 insertions(+), 5 deletions(-)
>
> diff --git a/bisect.c b/bisect.c
> index 385afaf875..367258b0dd 100644
> --- a/bisect.c
> +++ b/bisect.c
> @@ -806,13 +806,16 @@ static void handle_skipped_merge_base(const struct object_id *mb)
>   * "check_merge_bases" checks that merge bases are not "bad" (or "new").
>   *
>   * - If one is "bad" (or "new"), it means the user assumed something wrong
> - * and we must exit with a non 0 error code.
> + * and we must return error with a non 0 error code.
>   * - If one is "good" (or "old"), that's good, we have nothing to do.
>   * - If one is "skipped", we can't know but we should warn.
>   * - If we don't know, we should check it out and ask the user to test.
> + * - If a merge base must be tested, on success return -11 a special condition
> + * for early success, this will be converted back to 0 in check_good_are_ancestors_of_bad().
>   */
> -static void check_merge_bases(int rev_nr, struct commit **rev, int no_checkout)
> +static int check_merge_bases(int rev_nr, struct commit **rev, int no_checkout)
>  {
> +	int res = 0;
>  	struct commit_list *result;
>
>  	result = get_merge_bases_many(rev[0], rev_nr - 1, rev + 1);
> @@ -827,11 +830,16 @@ static void check_merge_bases(int rev_nr, struct commit **rev, int no_checkout)
>  			handle_skipped_merge_base(mb);
>  		} else {
>  			printf(_("Bisecting: a merge base must be tested\n"));
> -			exit(bisect_checkout(mb, no_checkout));
> +			res = bisect_checkout(mb, no_checkout);
> +			if (!res)
> +				/* indicate early success */
> +				res = -11;

> +			break;
>  		}
>  	}
>
>  	free_commit_list(result);
> +	return res;
>  }
>
>  static int check_ancestors(struct repository *r, int rev_nr,
> @@ -865,7 +873,7 @@ static void check_good_are_ancestors_of_bad(struct repository *r,
>  {
>  	char *filename = git_pathdup("BISECT_ANCESTORS_OK");
>  	struct stat st;
> -	int fd, rev_nr;
> +	int fd, rev_nr, res = 0;
>  	struct commit **rev;
>
>  	if (!current_bad_oid)
> @@ -880,10 +888,13 @@ static void check_good_are_ancestors_of_bad(struct repository *r,
>  		goto done;
>
>  	/* Check if all good revs are ancestor of the bad rev. */
> +
>  	rev = get_bad_and_good_commits(r, &rev_nr);
>  	if (check_ancestors(r, rev_nr, rev, prefix))
> -		check_merge_bases(rev_nr, rev, no_checkout);
> +		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);
> --
> 2.21.1 (Apple Git-122.3)
>
>