add assignment operator and unify memory pools

The unification of memory pools also fixed some memory leaks and
hopefully reduced the mallocs of identifier strings significantly by
giving them the same pool as the token stream.

util.h

@@ -41,11 +41,23 @@ void set_err(const char *fmt, ...);
 #define IS_ALPHA(c) ((c >= 'A' && c <= 'Z') || (c >= 'a' && c <= 'z') || c == '_')
 #define IS_ALNUM(c) (IS_ALPHA(c) || IS_NUM(c))
 
+/* Useful for efficiently allocating lots of data that can all be freed at once afterwards. */
+typedef struct Pool {
+	struct Pool *next;
+	void *data;
+	size_t len, cap;
+} Pool;
+Pool *pool_new(size_t init_cap); /* You usually want init_cap to be pretty high. */
+void pool_term(Pool *p);
+void *pool_alloc(Pool *p, size_t bytes);
+
 #define streq(a, b) (strcmp(a, b) == 0)
 /* check if a null-terminated string and a non-null-terminated string are equal */
 static inline bool streq_0_n(const char *a, const char *b, size_t bn) { return bn == strlen(a) ? strncmp(a, b, bn) == 0 : false; }
-/* a more trusting version of strndup; also for systems that don't have strndup */
+/* a more trusting version of strndup */
 char *sndup(const char *s, size_t n);
+/* sndup with memory pools */
+char *psndup(Pool *p, const char *s, size_t n);
 /* convert a non-null-terminated string to an intmax_t */
 intmax_t stoimax(const char *s, size_t n, size_t base, ssize_t *endpos /* -1 on success */);
 /* convert a non-null-terminated string to a double */