assert NOARG/NONEG behavior of parse-options callbacks

When we define a parse-options callback, the flags we put in the option
struct must match what the callback expects. For example, a callback
which does not handle the "unset" parameter should only be used with
PARSE_OPT_NONEG. But since the callback and the option struct are not
defined next to each other, it's easy to get this wrong (as earlier
patches in this series show).

Fortunately, the compiler can help us here: compiling with
-Wunused-parameters can show us which callbacks ignore their "unset"
parameters (and likewise, ones that ignore "arg" expect to be triggered
with PARSE_OPT_NOARG).

But after we've inspected a callback and determined that all of its
callers use the right flags, what do we do next? We'd like to silence
the compiler warning, but do so in a way that will catch any wrong calls
in the future.

We can do that by actually checking those variables and asserting that
they match our expectations. Because this is such a common pattern,
we'll introduce some helper macros. The resulting messages aren't
as descriptive as we could make them, but the file/line information from
BUG() is enough to identify the problem (and anyway, the point is that
these should never be seen).

Each of the annotated callbacks in this patch triggers
-Wunused-parameters, and was manually inspected to make sure all callers
use the correct options (so none of these BUGs should be triggerable).

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

apply.c

@@ -4772,6 +4772,9 @@ static int apply_option_parse_exclude(const struct option *opt,
 				      const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	add_name_limit(state, arg, 1);
 	return 0;
 }
@@ -4780,6 +4783,9 @@ static int apply_option_parse_include(const struct option *opt,
 				      const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	add_name_limit(state, arg, 0);
 	state->has_include = 1;
 	return 0;
@@ -4790,6 +4796,9 @@ static int apply_option_parse_p(const struct option *opt,
 				int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	state->p_value = atoi(arg);
 	state->p_value_known = 1;
 	return 0;
@@ -4799,6 +4808,9 @@ static int apply_option_parse_space_change(const struct option *opt,
 					   const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_ARG(arg);
+
 	if (unset)
 		state->ws_ignore_action = ignore_ws_none;
 	else
@@ -4810,6 +4822,9 @@ static int apply_option_parse_whitespace(const struct option *opt,
 					 const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	state->whitespace_option = arg;
 	if (parse_whitespace_option(state, arg))
 		return -1;
@@ -4820,6 +4835,9 @@ static int apply_option_parse_directory(const struct option *opt,
 					const char *arg, int unset)
 {
 	struct apply_state *state = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	strbuf_reset(&state->root);
 	strbuf_addstr(&state->root, arg);
 	strbuf_complete(&state->root, '/');

builtin/blame.c

@@ -732,6 +732,8 @@ static int blame_copy_callback(const struct option *option, const char *arg, int
 {
 	int *opt = option->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	/*
 	 * -C enables copy from removed files;
 	 * -C -C enables copy from existing files, but only
@@ -754,6 +756,8 @@ static int blame_move_callback(const struct option *option, const char *arg, int
 {
 	int *opt = option->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	*opt |= PICKAXE_BLAME_MOVE;
 
 	if (arg)

builtin/cat-file.c

@@ -595,6 +595,8 @@ static int batch_option_callback(const struct option *opt,
 {
 	struct batch_options *bo = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (bo->enabled) {
 		return error(_("only one batch option may be specified"));
 	}

builtin/checkout-index.c

@@ -132,6 +132,8 @@ static const char * const builtin_checkout_index_usage[] = {
 static int option_parse_stage(const struct option *opt,
 			      const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+
 	if (!strcmp(arg, "all")) {
 		to_tempfile = 1;
 		checkout_stage = CHECKOUT_ALL;

builtin/clean.c

@@ -140,6 +140,7 @@ static void clean_print_color(enum color_clean ix)
 static int exclude_cb(const struct option *opt, const char *arg, int unset)
 {
 	struct string_list *exclude_list = opt->value;
+	BUG_ON_OPT_NEG(unset);
 	string_list_append(exclude_list, arg);
 	return 0;
 }

builtin/commit.c

@@ -161,6 +161,9 @@ static int opt_parse_m(const struct option *opt, const char *arg, int unset)
 static int opt_parse_rename_score(const struct option *opt, const char *arg, int unset)
 {
 	const char **value = opt->value;
+
+	BUG_ON_OPT_NEG(unset);
+
 	if (arg != NULL && *arg == '=')
 		arg = arg + 1;
 

builtin/fetch.c

@@ -98,6 +98,8 @@ static int git_fetch_config(const char *k, const char *v, void *cb)
 
 static int parse_refmap_arg(const struct option *opt, const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+
 	/*
 	 * "git fetch --refmap='' origin foo"
 	 * can be used to tell the command not to store anywhere

builtin/grep.c

@@ -712,11 +712,14 @@ static int context_callback(const struct option *opt, const char *arg,
 static int file_callback(const struct option *opt, const char *arg, int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
-	int from_stdin = !strcmp(arg, "-");
+	int from_stdin;
 	FILE *patterns;
 	int lno = 0;
 	struct strbuf sb = STRBUF_INIT;
 
+	BUG_ON_OPT_NEG(unset);
+
+	from_stdin = !strcmp(arg, "-");
 	patterns = from_stdin ? stdin : fopen(arg, "r");
 	if (!patterns)
 		die_errno(_("cannot open '%s'"), arg);
@@ -737,6 +740,8 @@ static int file_callback(const struct option *opt, const char *arg, int unset)
 static int not_callback(const struct option *opt, const char *arg, int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	append_grep_pattern(grep_opt, "--not", "command line", 0, GREP_NOT);
 	return 0;
 }
@@ -744,6 +749,8 @@ static int not_callback(const struct option *opt, const char *arg, int unset)
 static int and_callback(const struct option *opt, const char *arg, int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	append_grep_pattern(grep_opt, "--and", "command line", 0, GREP_AND);
 	return 0;
 }
@@ -751,6 +758,8 @@ static int and_callback(const struct option *opt, const char *arg, int unset)
 static int open_callback(const struct option *opt, const char *arg, int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	append_grep_pattern(grep_opt, "(", "command line", 0, GREP_OPEN_PAREN);
 	return 0;
 }
@@ -758,6 +767,8 @@ static int open_callback(const struct option *opt, const char *arg, int unset)
 static int close_callback(const struct option *opt, const char *arg, int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	append_grep_pattern(grep_opt, ")", "command line", 0, GREP_CLOSE_PAREN);
 	return 0;
 }
@@ -766,6 +777,7 @@ static int pattern_callback(const struct option *opt, const char *arg,
 			    int unset)
 {
 	struct grep_opt *grep_opt = opt->value;
+	BUG_ON_OPT_NEG(unset);
 	append_grep_pattern(grep_opt, arg, "-e option", 0, GREP_PATTERN);
 	return 0;
 }

builtin/init-db.c

@@ -451,6 +451,7 @@ static int guess_repository_type(const char *git_dir)
 
 static int shared_callback(const struct option *opt, const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	*((int *) opt->value) = (arg) ? git_config_perm("arg", arg) : PERM_GROUP;
 	return 0;
 }

builtin/interpret-trailers.c

@@ -80,6 +80,8 @@ static int parse_opt_parse(const struct option *opt, const char *arg,
 	v->only_trailers = 1;
 	v->only_input = 1;
 	v->unfold = 1;
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	return 0;
 }
 

builtin/log.c

@@ -107,6 +107,8 @@ static int log_line_range_callback(const struct option *option, const char *arg,
 {
 	struct line_opt_callback_data *data = option->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (!arg)
 		return -1;
 
@@ -1151,6 +1153,8 @@ static int keep_subject = 0;
 
 static int keep_callback(const struct option *opt, const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	((struct rev_info *)opt->value)->total = -1;
 	keep_subject = 1;
 	return 0;
@@ -1161,6 +1165,7 @@ static int subject_prefix = 0;
 static int subject_prefix_callback(const struct option *opt, const char *arg,
 			    int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	subject_prefix = 1;
 	((struct rev_info *)opt->value)->subject_prefix = arg;
 	return 0;
@@ -1168,6 +1173,8 @@ static int subject_prefix_callback(const struct option *opt, const char *arg,
 
 static int rfc_callback(const struct option *opt, const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	return subject_prefix_callback(opt, "RFC PATCH", unset);
 }
 
@@ -1176,6 +1183,7 @@ static int numbered_cmdline_opt = 0;
 static int numbered_callback(const struct option *opt, const char *arg,
 			     int unset)
 {
+	BUG_ON_OPT_ARG(arg);
 	*(int *)opt->value = numbered_cmdline_opt = unset ? 0 : 1;
 	if (unset)
 		auto_number =  0;
@@ -1185,6 +1193,7 @@ static int numbered_callback(const struct option *opt, const char *arg,
 static int no_numbered_callback(const struct option *opt, const char *arg,
 				int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	return numbered_callback(opt, arg, 1);
 }
 
@@ -1192,6 +1201,7 @@ static int output_directory_callback(const struct option *opt, const char *arg,
 			      int unset)
 {
 	const char **dir = (const char **)opt->value;
+	BUG_ON_OPT_NEG(unset);
 	if (*dir)
 		die(_("Two output directories?"));
 	*dir = arg;

builtin/ls-files.c

@@ -475,6 +475,8 @@ static int option_parse_exclude(const struct option *opt,
 {
 	struct string_list *exclude_list = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	exc_given = 1;
 	string_list_append(exclude_list, arg);
 
@@ -486,6 +488,8 @@ static int option_parse_exclude_from(const struct option *opt,
 {
 	struct dir_struct *dir = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	exc_given = 1;
 	add_excludes_from_file(dir, arg);
 
@@ -497,6 +501,9 @@ static int option_parse_exclude_standard(const struct option *opt,
 {
 	struct dir_struct *dir = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
+
 	exc_given = 1;
 	setup_standard_excludes(dir);
 

builtin/merge-file.c

@@ -15,6 +15,8 @@ static int label_cb(const struct option *opt, const char *arg, int unset)
 	static int label_count = 0;
 	const char **names = (const char **)opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (label_count >= 3)
 		return error("too many labels on the command line");
 	names[label_count++] = arg;

builtin/merge.c

@@ -224,6 +224,7 @@ static int option_parse_x(const struct option *opt,
 static int option_parse_n(const struct option *opt,
 			  const char *arg, int unset)
 {
+	BUG_ON_OPT_ARG(arg);
 	show_diffstat = unset;
 	return 0;
 }

builtin/notes.c

@@ -215,6 +215,8 @@ static int parse_msg_arg(const struct option *opt, const char *arg, int unset)
 {
 	struct note_data *d = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	strbuf_grow(&d->buf, strlen(arg) + 2);
 	if (d->buf.len)
 		strbuf_addch(&d->buf, '\n');
@@ -229,6 +231,8 @@ static int parse_file_arg(const struct option *opt, const char *arg, int unset)
 {
 	struct note_data *d = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (d->buf.len)
 		strbuf_addch(&d->buf, '\n');
 	if (!strcmp(arg, "-")) {
@@ -250,6 +254,8 @@ static int parse_reuse_arg(const struct option *opt, const char *arg, int unset)
 	enum object_type type;
 	unsigned long len;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (d->buf.len)
 		strbuf_addch(&d->buf, '\n');
 
@@ -273,6 +279,7 @@ static int parse_reuse_arg(const struct option *opt, const char *arg, int unset)
 static int parse_reedit_arg(const struct option *opt, const char *arg, int unset)
 {
 	struct note_data *d = opt->value;
+	BUG_ON_OPT_NEG(unset);
 	d->use_editor = 1;
 	return parse_reuse_arg(opt, arg, unset);
 }

builtin/pack-objects.c

@@ -3206,6 +3206,9 @@ static int option_parse_index_version(const struct option *opt,
 {
 	char *c;
 	const char *val = arg;
+
+	BUG_ON_OPT_NEG(unset);
+
 	pack_idx_opts.version = strtoul(val, &c, 10);
 	if (pack_idx_opts.version > 2)
 		die(_("unsupported index version %s"), val);

builtin/read-tree.c

@@ -44,6 +44,7 @@ static const char * const read_tree_usage[] = {
 static int index_output_cb(const struct option *opt, const char *arg,
 				 int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	set_alternate_index_output(arg);
 	return 0;
 }
@@ -54,6 +55,8 @@ static int exclude_per_directory_cb(const struct option *opt, const char *arg,
 	struct dir_struct *dir;
 	struct unpack_trees_options *opts;
 
+	BUG_ON_OPT_NEG(unset);
+
 	opts = (struct unpack_trees_options *)opt->value;
 
 	if (opts->dir)

builtin/rebase.c

@@ -703,6 +703,9 @@ static int parse_opt_merge(const struct option *opt, const char *arg, int unset)
 {
 	struct rebase_options *opts = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
+
 	if (!is_interactive(opts))
 		opts->type = REBASE_MERGE;
 
@@ -715,6 +718,9 @@ static int parse_opt_interactive(const struct option *opt, const char *arg,
 {
 	struct rebase_options *opts = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
+
 	opts->type = REBASE_INTERACTIVE;
 	opts->flags |= REBASE_INTERACTIVE_EXPLICIT;
 

builtin/show-branch.c

@@ -604,6 +604,7 @@ static int parse_reflog_param(const struct option *opt, const char *arg,
 {
 	char *ep;
 	const char **base = (const char **)opt->value;
+	BUG_ON_OPT_NEG(unset);
 	if (!arg)
 		arg = "";
 	reflog = strtoul(arg, &ep, 10);

builtin/show-ref.c

@@ -151,6 +151,7 @@ static int hash_callback(const struct option *opt, const char *arg, int unset)
 static int exclude_existing_callback(const struct option *opt, const char *arg,
 				     int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	exclude_arg = 1;
 	*(const char **)opt->value = arg;
 	return 0;

builtin/tag.c

@@ -338,6 +338,8 @@ static int parse_msg_arg(const struct option *opt, const char *arg, int unset)
 {
 	struct msg_arg *msg = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (!arg)
 		return -1;
 	if (msg->buf.len)

builtin/update-index.c

@@ -790,12 +790,16 @@ static int refresh(struct refresh_params *o, unsigned int flag)
 static int refresh_callback(const struct option *opt,
 				const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	return refresh(opt->value, 0);
 }
 
 static int really_refresh_callback(const struct option *opt,
 				const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	return refresh(opt->value, REFRESH_REALLY);
 }
 
@@ -803,6 +807,7 @@ static int chmod_callback(const struct option *opt,
 				const char *arg, int unset)
 {
 	char *flip = opt->value;
+	BUG_ON_OPT_NEG(unset);
 	if ((arg[0] != '-' && arg[0] != '+') || arg[1] != 'x' || arg[2])
 		return error("option 'chmod' expects \"+x\" or \"-x\"");
 	*flip = arg[0];
@@ -812,6 +817,8 @@ static int chmod_callback(const struct option *opt,
 static int resolve_undo_clear_callback(const struct option *opt,
 				const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
+	BUG_ON_OPT_ARG(arg);
 	resolve_undo_clear();
 	return 0;
 }
@@ -847,6 +854,8 @@ static int cacheinfo_callback(struct parse_opt_ctx_t *ctx,
 	unsigned int mode;
 	const char *path;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (!parse_new_style_cacheinfo(ctx->argv[1], &mode, &oid, &path)) {
 		if (add_cacheinfo(mode, &oid, path, 0))
 			die("git update-index: --cacheinfo cannot add %s", path);
@@ -869,6 +878,8 @@ static int stdin_cacheinfo_callback(struct parse_opt_ctx_t *ctx,
 {
 	int *nul_term_line = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (ctx->argc != 1)
 		return error("option '%s' must be the last argument", opt->long_name);
 	allow_add = allow_replace = allow_remove = 1;
@@ -881,6 +892,8 @@ static int stdin_callback(struct parse_opt_ctx_t *ctx,
 {
 	int *read_from_stdin = opt->value;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (ctx->argc != 1)
 		return error("option '%s' must be the last argument", opt->long_name);
 	*read_from_stdin = 1;
@@ -888,11 +901,13 @@ static int stdin_callback(struct parse_opt_ctx_t *ctx,
 }
 
 static int unresolve_callback(struct parse_opt_ctx_t *ctx,
-				const struct option *opt, int flags)
+				const struct option *opt, int unset)
 {
 	int *has_errors = opt->value;
 	const char *prefix = startup_info->prefix;
 
+	BUG_ON_OPT_NEG(unset);
+
 	/* consume remaining arguments. */
 	*has_errors = do_unresolve(ctx->argc, ctx->argv,
 				prefix, prefix ? strlen(prefix) : 0);
@@ -905,11 +920,13 @@ static int unresolve_callback(struct parse_opt_ctx_t *ctx,
 }
 
 static int reupdate_callback(struct parse_opt_ctx_t *ctx,
-				const struct option *opt, int flags)
+				const struct option *opt, int unset)
 {
 	int *has_errors = opt->value;
 	const char *prefix = startup_info->prefix;
 
+	BUG_ON_OPT_NEG(unset);
+
 	/* consume remaining arguments. */
 	setup_work_tree();
 	*has_errors = do_reupdate(ctx->argc, ctx->argv,

parse-options-cb.c

@@ -58,6 +58,8 @@ int parse_opt_verbosity_cb(const struct option *opt, const char *arg,
 {
 	int *target = opt->value;
 
+	BUG_ON_OPT_ARG(arg);
+
 	if (unset)
 		/* --no-quiet, --no-verbose */
 		*target = 0;
@@ -80,6 +82,8 @@ int parse_opt_commits(const struct option *opt, const char *arg, int unset)
 	struct object_id oid;
 	struct commit *commit;
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (!arg)
 		return -1;
 	if (get_oid(arg, &oid))
@@ -110,6 +114,9 @@ int parse_opt_object_name(const struct option *opt, const char *arg, int unset)
 int parse_opt_tertiary(const struct option *opt, const char *arg, int unset)
 {
 	int *target = opt->value;
+
+	BUG_ON_OPT_ARG(arg);
+
 	*target = unset ? 2 : 1;
 	return 0;
 }

parse-options.h

@@ -191,6 +191,20 @@ extern int opterror(const struct option *opt, const char *reason, int flags);
 #define opterror(o,r,f) (opterror((o),(r),(f)), const_error())
 #endif
 
+/*
+ * Use these assertions for callbacks that expect to be called with NONEG and
+ * NOARG respectively, and do not otherwise handle the "unset" and "arg"
+ * parameters.
+ */
+#define BUG_ON_OPT_NEG(unset) do { \
+	if ((unset)) \
+		BUG("option callback does not expect negation"); \
+} while (0)
+#define BUG_ON_OPT_ARG(arg) do { \
+	if ((arg)) \
+		BUG("option callback does not expect an argument"); \
+} while (0)
+
 /*----- incremental advanced APIs -----*/
 
 enum {

ref-filter.c

@@ -2316,6 +2316,8 @@ int parse_opt_merge_filter(const struct option *opt, const char *arg, int unset)
 	struct object_id oid;
 	int no_merged = starts_with(opt->long_name, "no");
 
+	BUG_ON_OPT_NEG(unset);
+
 	if (rf->merge) {
 		if (no_merged) {
 			return opterror(opt, "is incompatible with --merged", 0);

t/helper/test-parse-options.c

@@ -36,6 +36,7 @@ static int length_callback(const struct option *opt, const char *arg, int unset)
 
 static int number_callback(const struct option *opt, const char *arg, int unset)
 {
+	BUG_ON_OPT_NEG(unset);
 	*(int *)opt->value = strtol(arg, NULL, 10);
 	return 0;
 }