Bug: Call hook may be called twice when count hook yields

Took the opportunity and moved the code that controls call hooks
in 'luaV_execute' into a function.

ldebug.c

@@ -865,6 +865,28 @@ static int changedline (const Proto *p, int oldpc, int newpc) {
 }
 
 
+/*
+** Traces Lua calls. If code is running the first instruction of a function,
+** and function is not vararg, and it is not coming from an yield,
+** calls 'luaD_hookcall'. (Vararg functions will call 'luaD_hookcall'
+** after adjusting its variable arguments; otherwise, they could call
+** a line/count hook before the call hook. Functions coming from
+** an yield already called 'luaD_hookcall' before yielding.)
+*/
+int luaG_tracecall (lua_State *L) {
+  CallInfo *ci = L->ci;
+  Proto *p = ci_func(ci)->p;
+  ci->u.l.trap = 1;  /* ensure hooks will be checked */
+  if (ci->u.l.savedpc == p->code) {  /* first instruction (not resuming)? */
+    if (p->is_vararg)
+      return 0;  /* hooks will start at VARARGPREP instruction */
+    else if (!(ci->callstatus & CIST_HOOKYIELD))  /* not yieded? */
+      luaD_hookcall(L, ci);  /* check 'call' hook */
+  }
+  return 1;  /* keep 'trap' on */
+}
+
+
 /*
 ** Traces the execution of a Lua function. Called before the execution
 ** of each opcode, when debug is on. 'L->oldpc' stores the last

ldebug.h

@@ -58,6 +58,7 @@ LUAI_FUNC const char *luaG_addinfo (lua_State *L, const char *msg,
                                                   TString *src, int line);
 LUAI_FUNC l_noret luaG_errormsg (lua_State *L);
 LUAI_FUNC int luaG_traceexec (lua_State *L, const Instruction *pc);
+LUAI_FUNC int luaG_tracecall (lua_State *L);
 
 
 #endif

lstate.h

@@ -181,7 +181,7 @@ struct CallInfo {
   union {
     struct {  /* only for Lua functions */
       const Instruction *savedpc;
-      volatile l_signalT trap;
+      volatile l_signalT trap;  /* function is tracing lines/counts */
       int nextraargs;  /* # of extra arguments in vararg functions */
     } l;
     struct {  /* only for C functions */

lvm.c

@@ -1157,18 +1157,11 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
  startfunc:
   trap = L->hookmask;
  returning:  /* trap already set */
-  cl = clLvalue(s2v(ci->func.p));
+  cl = ci_func(ci);
   k = cl->p->k;
   pc = ci->u.l.savedpc;
-  if (l_unlikely(trap)) {
-    if (pc == cl->p->code) {  /* first instruction (not resuming)? */
-      if (cl->p->is_vararg)
-        trap = 0;  /* hooks will start after VARARGPREP instruction */
-      else  /* check 'call' hook */
-        luaD_hookcall(L, ci);
-    }
-    ci->u.l.trap = 1;  /* assume trap is on, for now */
-  }
+  if (l_unlikely(trap))
+    trap = luaG_tracecall(L);
   base = ci->func.p + 1;
   /* main loop of interpreter */
   for (;;) {