Merge pull request #1380 from suzukaze/refactor-pool.c

Replace 0 with NULL because struct pointer is set NULL in.

src/pool.c

@@ -53,7 +53,7 @@ mrb_pool_open(mrb_state *mrb)
 
   if (pool) {
     pool->mrb = mrb;
-    pool->pages = 0;
+    pool->pages = NULL;
   }
 
   return pool;
@@ -96,7 +96,7 @@ mrb_pool_alloc(mrb_pool *pool, size_t len)
   struct mrb_pool_page *page;
   size_t n;
 
-  if (!pool) return 0;
+  if (!pool) return NULL;
   len += ALIGN_PADDING(len);
   page = pool->pages;
   while (page) {
@@ -109,7 +109,7 @@ mrb_pool_alloc(mrb_pool *pool, size_t len)
     page = page->next;
   }
   page = page_alloc(pool, len);
-  if (!page) return 0;
+  if (!page) return NULL;
   page->offset = len;
   page->next = pool->pages;
   pool->pages = page;
@@ -145,7 +145,7 @@ mrb_pool_realloc(mrb_pool *pool, void *p, size_t oldlen, size_t newlen)
   struct mrb_pool_page *page;
   void *np;
 
-  if (!pool) return 0;
+  if (!pool) return NULL;
   oldlen += ALIGN_PADDING(oldlen);
   newlen += ALIGN_PADDING(newlen);
   page = pool->pages;
@@ -177,7 +177,7 @@ main(void)
   mrb_pool *pool;
   void *p;
 
-  pool = mrb_pool_open(0);
+  pool = mrb_pool_open(NULL);
   p = mrb_pool_alloc(pool, len);
   for (i=1; i<20; i++) {
     printf("%p (len=%d) %ud\n", p, len, mrb_pool_can_realloc(pool, p, len*2));