Re: lua_getlocal crashes after yield from a debug hook

[Roberto Ierusalimschy <roberto@...>]

> I try to fix it, but maybe there is a better solution :)

Maybe this one?

-- Roberto

===================================================================
RCS file: RCS/ldebug.c,v
retrieving revision 2.110
diff -u2 -r2.110 ldebug.c
--- ldebug.c	2015/01/02 12:52:22	2.110
+++ ldebug.c	2015/02/13 12:33:20
@@ -50,4 +50,20 @@
 
 /*
+** If function yielded, its 'func' can be in the 'extra' field. The
+** next function restores 'func' to its correct value for debugging
+** purposes. (It exchanges 'func' and 'extra'; so, when called again,
+** after debugging, it also "re-restores" ** 'func' to its altered value.
+*/
+static void swapextra (lua_State *L) {
+  if (L->status == LUA_YIELD) {
+    CallInfo *ci = L->ci;  /* get function that yielded */
+    StkId temp = ci->func;  /* exchange its 'func' and 'extra' values */
+    ci->func = restorestack(L, ci->extra);
+    ci->extra = savestack(L, temp);
+  }
+}
+
+
+/*
 ** this function can be called asynchronous (e.g. during a signal)
 */
@@ -145,4 +161,5 @@
   const char *name;
   lua_lock(L);
+  swapextra(L);
   if (ar == NULL) {  /* information about non-active function? */
     if (!isLfunction(L->top - 1))  /* not a Lua function? */
@@ -159,4 +176,5 @@
     }
   }
+  swapextra(L);
   lua_unlock(L);
   return name;
@@ -166,10 +184,13 @@
 LUA_API const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n) {
   StkId pos = 0;  /* to avoid warnings */
-  const char *name = findlocal(L, ar->i_ci, n, &pos);
+  const char *name;
   lua_lock(L);
+  swapextra(L);
+  name = findlocal(L, ar->i_ci, n, &pos);
   if (name) {
     setobjs2s(L, pos, L->top - 1);
     L->top--;  /* pop value */
   }
+  swapextra(L);
   lua_unlock(L);
   return name;
@@ -271,4 +292,5 @@
   StkId func;
   lua_lock(L);
+  swapextra(L);
   if (*what == '>') {
     ci = NULL;
@@ -289,4 +311,5 @@
     api_incr_top(L);
   }
+  swapextra(L);  /* correct before option 'L', which can raise a mem. error */
   if (strchr(what, 'L'))
     collectvalidlines(L, cl);