DEBUG: Try to catch stale pointer dereferences to buffers after they've grown.

In normal use some such bugs may not be noticed easily, because the buffer's
memory allocation size is large enough that when adding another element the
pointer doesn't change.

--HG--
branch : HEAD

diff --git a/src/lib/buffer.c b/src/lib/buffer.c
index 657b3824f9338dbe08add465d473521d1a5c1db9..f10a47e22888e76ad05361305ee940e8fbd621e1 100644 (file)
--- a/src/lib/buffer.c
+++ b/src/lib/buffer.c
@@ -63,6 +63,22 @@ buffer_check_limits(struct real_buffer *buf, size_t pos, size_t data_size)
                buffer_alloc(buf, pool_get_exp_grown_size(buf->pool, buf->alloc,
                                                          new_size));
        }
+#ifdef DEBUG
+       else if (new_size > buf->used && buf->alloced &&
+                !buf->pool->alloconly_pool && !buf->pool->datastack_pool) {
+               void *new_buf;
+
+               /* buffer's size increased: move the buffer's memory elsewhere.
+                  this should help catch bugs where old pointers are tried to
+                  be used to access the buffer's memory */
+               new_buf = p_malloc(buf->pool, buf->alloc);
+               memcpy(new_buf, buf->w_buffer, buf->alloc);
+               p_free(buf->pool, buf->w_buffer);
+
+               buf->w_buffer = new_buf;
+               buf->r_buffer = new_buf;
+       }
+#endif
 
        if (new_size > buf->used)
                buf->used = new_size;