coccinelle: add reallocarray() coccinelle script

Let's systematically make use of reallocarray() whereever we invoke
realloc() with a product of two values.

src/basic/env-util.c

@@ -721,7 +721,7 @@ char **replace_env_argv(char **argv, char **env) {
                         q = strv_length(m);
                         l = l + q - 1;
 
-                        w = realloc(ret, sizeof(char*) * (l+1));
+                        w = reallocarray(ret, l + 1, sizeof(char *));
                         if (!w) {
                                 ret[k] = NULL;
                                 strv_free(ret);

src/basic/prioq.c

@@ -173,7 +173,7 @@ int prioq_put(Prioq *q, void *data, unsigned *idx) {
                 struct prioq_item *j;
 
                 n = MAX((q->n_items+1) * 2, 16u);
-                j = realloc(q->items, sizeof(struct prioq_item) * n);
+                j = reallocarray(q->items, n, sizeof(struct prioq_item));
                 if (!j)
                         return -ENOMEM;
 

src/basic/strbuf.c

@@ -190,7 +190,7 @@ ssize_t strbuf_add_string(struct strbuf *str, const char *s, size_t len) {
         node_child->value_len = len;
 
         /* extend array, add new entry, sort for bisection */
-        child = realloc(node->children, (node->children_count + 1) * sizeof(struct strbuf_child_entry));
+        child = reallocarray(node->children, node->children_count + 1, sizeof(struct strbuf_child_entry));
         if (!child) {
                 free(node_child);
                 return -ENOMEM;

src/basic/strv.c

@@ -214,7 +214,7 @@ int strv_extend_strv(char ***a, char **b, bool filter_duplicates) {
         p = strv_length(*a);
         q = strv_length(b);
 
-        t = realloc(*a, sizeof(char*) * (p + q + 1));
+        t = reallocarray(*a, p + q + 1, sizeof(char *));
         if (!t)
                 return -ENOMEM;
 
@@ -861,7 +861,7 @@ int strv_extend_n(char ***l, const char *value, size_t n) {
 
         k = strv_length(*l);
 
-        nl = realloc(*l, sizeof(char*) * (k + n + 1));
+        nl = reallocarray(*l, k + n + 1, sizeof(char *));
         if (!nl)
                 return -ENOMEM;