Added assertions for proper use of string buffers
diff --git a/lauxlib.c b/lauxlib.c
index 2610f90..94835ef 100644
--- a/lauxlib.c
+++ b/lauxlib.c
@@ -516,6 +516,15 @@
/*
+** Whenever buffer is accessed, slot 'idx' must either be a box (which
+** cannot be NULL) or it is a placeholder for the buffer.
+*/
+#define checkbufferlevel(B,idx) \
+ lua_assert(buffonstack(B) ? lua_touserdata(B->L, idx) != NULL \
+ : lua_touserdata(B->L, idx) == (void*)B)
+
+
+/*
** Compute new size for buffer 'B', enough to accommodate extra 'sz'
** bytes.
*/
@@ -531,10 +540,11 @@
/*
** Returns a pointer to a free area with at least 'sz' bytes in buffer
-** 'B'. 'boxidx' is the relative position in the stack where the
-** buffer's box is or should be.
+** 'B'. 'boxidx' is the relative position in the stack where is the
+** buffer's box or its placeholder.
*/
static char *prepbuffsize (luaL_Buffer *B, size_t sz, int boxidx) {
+ checkbufferlevel(B, boxidx);
if (B->size - B->n >= sz) /* enough space? */
return B->b + B->n;
else {
@@ -545,6 +555,7 @@
if (buffonstack(B)) /* buffer already has a box? */
newbuff = (char *)resizebox(L, boxidx, newsize); /* resize it */
else { /* no box yet */
+ lua_remove(L, boxidx); /* remove placeholder */
newbox(L); /* create a new box */
lua_insert(L, boxidx); /* move box to its intended position */
lua_toclose(L, boxidx);
@@ -581,11 +592,11 @@
LUALIB_API void luaL_pushresult (luaL_Buffer *B) {
lua_State *L = B->L;
+ checkbufferlevel(B, -1);
lua_pushlstring(L, B->b, B->n);
- if (buffonstack(B)) {
+ if (buffonstack(B))
lua_closeslot(L, -2); /* close the box */
- lua_remove(L, -2); /* remove box from the stack */
- }
+ lua_remove(L, -2); /* remove box or placeholder from the stack */
}
@@ -620,6 +631,7 @@
B->b = B->init.b;
B->n = 0;
B->size = LUAL_BUFFERSIZE;
+ lua_pushlightuserdata(L, (void*)B); /* push placeholder */
}
