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parse-options: prefer opt->value to globals in callbacks

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We have several parse-options callbacks that ignore their "opt"
parameters entirely. This is a little unusual, as we'd normally put the
result of the parsing into opt->value. In the case of these callbacks,
though, they directly manipulate global variables instead (and in
most cases the caller sets opt->value to NULL in the OPT_CALLBACK
declaration).

The immediate symptom we'd like to deal with is that the unused "opt"
variables trigger -Wunused-parameter. But how to fix that is debatable.
One option is to annotate them with UNUSED. But another is to have the
caller pass in the appropriate variable via opt->value, and use it. That
has the benefit of making the callbacks reusable (in theory at least),
and makes it clear from the OPT_CALLBACK declaration which variables
will be affected (doubly so for the cases in builtin/fast-export.c,
where we do set opt->value, but it is completely ignored!).

The slight downside is that we lose type safety, since they're now
passing through void pointers.

I went with the "just use them" approach here. The loss of type safety
is unfortunate, but that is already an issue with most of the other
callbacks. If we want to try to address that, we should do so more
consistently (and this patch would prepare these callbacks for whatever
we choose to do there).

Note that in the cases in builtin/fast-export.c, we are passing
anonymous enums. We'll have to give them names so that we can declare
the appropriate pointer type within the callbacks.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Jeff King
2023-08-31 17:21:07 -04:00
committed by Junio C Hamano
parent 9b40386586
commit 66e3309294
6 changed files with 50 additions and 37 deletions
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8
builtin/checkout-index.c
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@ -193,14 +193,16 @@ static const char * const builtin_checkout_index_usage[] = {
static int option_parse_stage(const struct option *opt,
const char *arg, int unset)
{
int *stage = opt->value;
BUG_ON_OPT_NEG(unset);
if (!strcmp(arg, "all")) {
checkout_stage = CHECKOUT_ALL;
*stage = CHECKOUT_ALL;
} else {
int ch = arg[0];
if ('1' <= ch && ch <= '3')
checkout_stage = arg[0] - '0';
*stage = arg[0] - '0';
else
die(_("stage should be between 1 and 3 or all"));
}
@ -238,7 +240,7 @@ int cmd_checkout_index(int argc, const char **argv, const char *prefix)
N_("write the content to temporary files")),
OPT_STRING(0, "prefix", &state.base_dir, N_("string"),
N_("when creating files, prepend <string>")),
OPT_CALLBACK_F(0, "stage", NULL, "(1|2|3|all)",
OPT_CALLBACK_F(0, "stage", &checkout_stage, "(1|2|3|all)",
N_("copy out the files from named stage"),
PARSE_OPT_NONEG, option_parse_stage),
OPT_END()