fix xcalloc() argument order

Pass the number of elements first and ther size second, as expected
by xcalloc().  Provide a semantic patch, which was actually used to
generate the rest of this patch.

The semantic patch would generate flip-flop diffs if both arguments
are sizeofs.  We don't have such a case, and it's hard to imagine
the usefulness of such an allocation.  If it ever occurs then we
could deal with it by duplicating the rule in the semantic patch to
make it cancel itself out, or we could change the code to use
CALLOC_ARRAY.

Signed-off-by: René Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

add-interactive.c

@@ -413,7 +413,7 @@ struct file_item {
 
 static void add_file_item(struct string_list *files, const char *name)
 {
-	struct file_item *item = xcalloc(sizeof(*item), 1);
+	struct file_item *item = xcalloc(1, sizeof(*item));
 
 	string_list_append(files, name)->util = item;
 }
@@ -476,7 +476,7 @@ static void collect_changes_cb(struct diff_queue_struct *q,
 
 			add_file_item(s->files, name);
 
-			entry = xcalloc(sizeof(*entry), 1);
+			entry = xcalloc(1, sizeof(*entry));
 			hashmap_entry_init(&entry->ent, hash);
 			entry->name = s->files->items[s->files->nr - 1].string;
 			entry->item = s->files->items[s->files->nr - 1].util;
@@ -1120,7 +1120,7 @@ int run_add_i(struct repository *r, const struct pathspec *ps)
 	int res = 0;
 
 	for (i = 0; i < ARRAY_SIZE(command_list); i++) {
-		struct command_item *util = xcalloc(sizeof(*util), 1);
+		struct command_item *util = xcalloc(1, sizeof(*util));
 		util->command = command_list[i].command;
 		string_list_append(&commands.items, command_list[i].string)
 			->util = util;

blame.c

@@ -951,13 +951,13 @@ static int *fuzzy_find_matching_lines(struct blame_origin *parent,
 	max_search_distance_b = ((2 * max_search_distance_a + 1) * length_b
 				 - 1) / length_a;
 
-	result = xcalloc(sizeof(int), length_b);
-	second_best_result = xcalloc(sizeof(int), length_b);
-	certainties = xcalloc(sizeof(int), length_b);
+	result = xcalloc(length_b, sizeof(int));
+	second_best_result = xcalloc(length_b, sizeof(int));
+	certainties = xcalloc(length_b, sizeof(int));
 
 	/* See get_similarity() for details of similarities. */
 	similarity_count = length_b * (max_search_distance_a * 2 + 1);
-	similarities = xcalloc(sizeof(int), similarity_count);
+	similarities = xcalloc(similarity_count, sizeof(int));
 
 	for (i = 0; i < length_b; ++i) {
 		result[i] = -1;
@@ -995,7 +995,7 @@ static void fill_origin_fingerprints(struct blame_origin *o)
 		return;
 	o->num_lines = find_line_starts(&line_starts, o->file.ptr,
 					o->file.size);
-	o->fingerprints = xcalloc(sizeof(struct fingerprint), o->num_lines);
+	o->fingerprints = xcalloc(o->num_lines, sizeof(struct fingerprint));
 	get_line_fingerprints(o->fingerprints, o->file.ptr, line_starts,
 			      0, o->num_lines);
 	free(line_starts);
@@ -1853,8 +1853,8 @@ static void blame_chunk(struct blame_entry ***dstq, struct blame_entry ***srcq,
 	diffp = NULL;
 
 	if (ignore_diffs && same - tlno > 0) {
-		line_blames = xcalloc(sizeof(struct blame_line_tracker),
-				      same - tlno);
+		line_blames = xcalloc(same - tlno,
+				      sizeof(struct blame_line_tracker));
 		guess_line_blames(parent, target, tlno, offset, same,
 				  parent_len, line_blames);
 	}

contrib/coccinelle/xcalloc.cocci

@@ -0,0 +1,10 @@
+@@
+type T;
+T *ptr;
+expression n;
+@@
+  xcalloc(
++ n,
+  \( sizeof(T) \| sizeof(*ptr) \)
+- , n
+  )

range-diff.c

@@ -93,7 +93,7 @@ static int read_patches(const char *range, struct string_list *list,
 				string_list_append(list, buf.buf)->util = util;
 				strbuf_reset(&buf);
 			}
-			util = xcalloc(sizeof(*util), 1);
+			util = xcalloc(1, sizeof(*util));
 			if (get_oid(p, &util->oid)) {
 				error(_("could not parse commit '%s'"), p);
 				free(util);

ref-filter.c

@@ -768,7 +768,8 @@ static int if_atom_handler(struct atom_value *atomv, struct ref_formatting_state
 			   struct strbuf *unused_err)
 {
 	struct ref_formatting_stack *new_stack;
-	struct if_then_else *if_then_else = xcalloc(sizeof(struct if_then_else), 1);
+	struct if_then_else *if_then_else = xcalloc(1,
+						    sizeof(struct if_then_else));
 
 	if_then_else->str = atomv->atom->u.if_then_else.str;
 	if_then_else->cmp_status = atomv->atom->u.if_then_else.cmp_status;
@@ -2242,7 +2243,7 @@ static void reach_filter(struct ref_array *array,
 	if (!check_reachable)
 		return;
 
-	to_clear = xcalloc(sizeof(struct commit *), array->nr);
+	to_clear = xcalloc(array->nr, sizeof(struct commit *));
 
 	repo_init_revisions(the_repository, &revs, NULL);
 

trailer.c

@@ -174,7 +174,7 @@ static void print_all(FILE *outfile, struct list_head *head,
 
 static struct trailer_item *trailer_from_arg(struct arg_item *arg_tok)
 {
-	struct trailer_item *new_item = xcalloc(sizeof(*new_item), 1);
+	struct trailer_item *new_item = xcalloc(1, sizeof(*new_item));
 	new_item->token = arg_tok->token;
 	new_item->value = arg_tok->value;
 	arg_tok->token = arg_tok->value = NULL;
@@ -445,7 +445,7 @@ static struct arg_item *get_conf_item(const char *name)
 	}
 
 	/* Item does not already exists, create it */
-	item = xcalloc(sizeof(*item), 1);
+	item = xcalloc(1, sizeof(*item));
 	duplicate_conf(&item->conf, &default_conf_info);
 	item->conf.name = xstrdup(name);
 
@@ -664,7 +664,7 @@ static void parse_trailer(struct strbuf *tok, struct strbuf *val,
 static struct trailer_item *add_trailer_item(struct list_head *head, char *tok,
 					     char *val)
 {
-	struct trailer_item *new_item = xcalloc(sizeof(*new_item), 1);
+	struct trailer_item *new_item = xcalloc(1, sizeof(*new_item));
 	new_item->token = tok;
 	new_item->value = val;
 	list_add_tail(&new_item->list, head);
@@ -675,7 +675,7 @@ static void add_arg_item(struct list_head *arg_head, char *tok, char *val,
 			 const struct conf_info *conf,
 			 const struct new_trailer_item *new_trailer_item)
 {
-	struct arg_item *new_item = xcalloc(sizeof(*new_item), 1);
+	struct arg_item *new_item = xcalloc(1, sizeof(*new_item));
 	new_item->token = tok;
 	new_item->value = val;
 	duplicate_conf(&new_item->conf, conf);