Fixed "conceptual" bug in 'luaK_setreturns'

This function was computing invalid instruction addresses when the
expression was not a multi-return instruction. (Virtually all machines
don't raise errors when computing an invalid address, as long as the
address is not accessed, but this computation is undefined behavior in
ISO C.)

2 files changed, 5 insertions, 5 deletions

diff --git a/lcode.c b/lcode.c
index 83a6d064..6f241c94 100644
--- a/lcode.c
+++ b/lcode.c
@@ -703,19 +703,18 @@ static void const2exp (TValue *v, expdesc *e) {
 
 /*
 ** Fix an expression to return the number of results 'nresults'.
-** Either 'e' is a multi-ret expression (function call or vararg)
-** or 'nresults' is LUA_MULTRET (as any expression can satisfy that).
+** 'e' must be a multi-ret expression (function call or vararg).
 */
 void luaK_setreturns (FuncState *fs, expdesc *e, int nresults) {
   Instruction *pc = &getinstruction(fs, e);
   if (e->k == VCALL)  /* expression is an open function call? */
     SETARG_C(*pc, nresults + 1);
-  else if (e->k == VVARARG) {
+  else {
+    lua_assert(e->k == VVARARG);
     SETARG_C(*pc, nresults + 1);
     SETARG_A(*pc, fs->freereg);
     luaK_reserveregs(fs, 1);
   }
-  else lua_assert(nresults == LUA_MULTRET);
 }
 
 
diff --git a/lparser.c b/lparser.c
index 8c812039..b0dbb65c 100644
--- a/lparser.c
+++ b/lparser.c
@@ -1014,7 +1014,8 @@ static void funcargs (LexState *ls, expdesc *f, int line) {
         args.k = VVOID;
       else {
         explist(ls, &args);
-        luaK_setmultret(fs, &args);
+        if (hasmultret(args.k))
+          luaK_setmultret(fs, &args);
       }
       check_match(ls, ')', '(', line);
       break;