1 files changed, 39 insertions, 63 deletions

diff --git a/src/lua/lstate.h b/src/lua/lstate.h
index 1b6bcdf..cbcf07e 100644
--- a/src/lua/lstate.h
+++ b/src/lua/lstate.h
@@ -87,48 +87,12 @@
 
 
 /*
-** About 'nCcalls': each thread in Lua (a lua_State) keeps a count of
-** how many "C calls" it still can do in the C stack, to avoid C-stack
-** overflow.  This count is very rough approximation; it considers only
-** recursive functions inside the interpreter, as non-recursive calls
-** can be considered using a fixed (although unknown) amount of stack
-** space.
-**
-** The count has two parts: the lower part is the count itself; the
-** higher part counts the number of non-yieldable calls in the stack.
-** (They are together so that we can change both with one instruction.)
-**
-** Because calls to external C functions can use an unknown amount
-** of space (e.g., functions using an auxiliary buffer), calls
-** to these functions add more than one to the count (see CSTACKCF).
-**
-** The proper count excludes the number of CallInfo structures allocated
-** by Lua, as a kind of "potential" calls. So, when Lua calls a function
-** (and "consumes" one CallInfo), it needs neither to decrement nor to
-** check 'nCcalls', as its use of C stack is already accounted for.
-*/
-
-/* number of "C stack slots" used by an external C function */
-#define CSTACKCF        10
-
-
-/*
-** The C-stack size is sliced in the following zones:
-** - larger than CSTACKERR: normal stack;
-** - [CSTACKMARK, CSTACKERR]: buffer zone to signal a stack overflow;
-** - [CSTACKCF, CSTACKERRMARK]: error-handling zone;
-** - below CSTACKERRMARK: buffer zone to signal overflow during overflow;
-** (Because the counter can be decremented CSTACKCF at once, we need
-** the so called "buffer zones", with at least that size, to properly
-** detect a change from one zone to the next.)
+** About 'nCcalls':  This count has two parts: the lower 16 bits counts
+** the number of recursive invocations in the C stack; the higher
+** 16 bits counts the number of non-yieldable calls in the stack.
+** (They are together so that we can change and save both with one
+** instruction.)
 */
-#define CSTACKERR       (8 * CSTACKCF)
-#define CSTACKMARK      (CSTACKERR - (CSTACKCF + 2))
-#define CSTACKERRMARK   (CSTACKCF + 2)
-
-
-/* initial limit for the C-stack of threads */
-#define CSTACKTHREAD    (2 * CSTACKERR)
 
 
 /* true if this thread does not have non-yieldable calls in the stack */
@@ -144,13 +108,8 @@
 /* Decrement the number of non-yieldable calls */
 #define decnny(L)       ((L)->nCcalls -= 0x10000)
 
-/* Increment the number of non-yieldable calls and decrement nCcalls */
-#define incXCcalls(L)   ((L)->nCcalls += 0x10000 - CSTACKCF)
-
-/* Decrement the number of non-yieldable calls and increment nCcalls */
-#define decXCcalls(L)   ((L)->nCcalls -= 0x10000 - CSTACKCF)
-
-
+/* Non-yieldable call increment */
+#define nyci    (0x10000 | 1)
 
 
 
@@ -168,12 +127,20 @@ struct lua_longjmp;  /* defined in ldo.c */
 #endif
 
 
-/* extra stack space to handle TM calls and some other extras */
+/*
+** Extra stack space to handle TM calls and some other extras. This
+** space is not included in 'stack_last'. It is used only to avoid stack
+** checks, either because the element will be promptly popped or because
+** there will be a stack check soon after the push. Function frames
+** never use this extra space, so it does not need to be kept clean.
+*/
 #define EXTRA_STACK   5
 
 
 #define BASIC_STACK_SIZE        (2*LUA_MINSTACK)
 
+#define stacksize(th)   cast_int((th)->stack_last - (th)->stack)
+
 
 /* kinds of Garbage Collection */
 #define KGC_INC         0       /* incremental gc */
@@ -224,14 +191,15 @@ typedef struct CallInfo {
 */
 #define CIST_OAH        (1<<0)  /* original value of 'allowhook' */
 #define CIST_C          (1<<1)  /* call is running a C function */
-#define CIST_HOOKED     (1<<2)  /* call is running a debug hook */
-#define CIST_YPCALL     (1<<3)  /* call is a yieldable protected call */
-#define CIST_TAIL       (1<<4)  /* call was tail called */
-#define CIST_HOOKYIELD  (1<<5)  /* last hook called yielded */
-#define CIST_FIN        (1<<6)  /* call is running a finalizer */
-#define CIST_TRAN       (1<<7)  /* 'ci' has transfer information */
+#define CIST_FRESH      (1<<2)  /* call is on a fresh "luaV_execute" frame */
+#define CIST_HOOKED     (1<<3)  /* call is running a debug hook */
+#define CIST_YPCALL     (1<<4)  /* call is a yieldable protected call */
+#define CIST_TAIL       (1<<5)  /* call was tail called */
+#define CIST_HOOKYIELD  (1<<6)  /* last hook called yielded */
+#define CIST_FIN        (1<<7)  /* call is running a finalizer */
+#define CIST_TRAN       (1<<8)  /* 'ci' has transfer information */
 #if defined(LUA_COMPAT_LT_LE)
-#define CIST_LEQ        (1<<8)  /* using __lt for __le */
+#define CIST_LEQ        (1<<9)  /* using __lt for __le */
 #endif
 
 /* active function is a Lua function */
@@ -296,7 +264,6 @@ typedef struct global_State {
   TString *strcache[STRCACHE_N][STRCACHE_M];  /* cache for strings in API */
   lua_WarnFunction warnf;  /* warning function */
   void *ud_warn;         /* auxiliary data to 'warnf' */
-  unsigned int Cstacklimit;  /* current limit for the C stack */
 } global_State;
 
 
@@ -311,7 +278,7 @@ struct lua_State {
   StkId top;  /* first free slot in the stack */
   global_State *l_G;
   CallInfo *ci;  /* call info for current function */
-  StkId stack_last;  /* last free slot in the stack */
+  StkId stack_last;  /* end of stack (last element + 1) */
   StkId stack;  /* stack base */
   UpVal *openupval;  /* list of open upvalues in this stack */
   GCObject *gclist;
@@ -320,9 +287,8 @@ struct lua_State {
   CallInfo base_ci;  /* CallInfo for first level (C calling Lua) */
   volatile lua_Hook hook;
   ptrdiff_t errfunc;  /* current error handling function (stack index) */
-  l_uint32 nCcalls;  /* number of allowed nested C calls - 'nci' */
+  l_uint32 nCcalls;  /* number of nested (non-yieldable | C)  calls */
   int oldpc;  /* last pc traced */
-  int stacksize;
   int basehookcount;
   int hookcount;
   volatile l_signalT hookmask;
@@ -334,6 +300,12 @@ struct lua_State {
 
 /*
 ** Union of all collectable objects (only for conversions)
+** ISO C99, 6.5.2.3 p.5:
+** "if a union contains several structures that share a common initial
+** sequence [...], and if the union object currently contains one
+** of these structures, it is permitted to inspect the common initial
+** part of any of them anywhere that a declaration of the complete type
+** of the union is visible."
 */
 union GCUnion {
   GCObject gc;  /* common header */
@@ -347,6 +319,11 @@ union GCUnion {
 };
 
 
+/*
+** ISO C99, 6.7.2.1 p.14:
+** "A pointer to a union object, suitably converted, points to each of
+** its members [...], and vice versa."
+*/
 #define cast_u(o)       cast(union GCUnion *, (o))
 
 /* macros to convert a GCObject into a specific value */
@@ -378,12 +355,11 @@ LUAI_FUNC void luaE_freethread (lua_State *L, lua_State *L1);
 LUAI_FUNC CallInfo *luaE_extendCI (lua_State *L);
 LUAI_FUNC void luaE_freeCI (lua_State *L);
 LUAI_FUNC void luaE_shrinkCI (lua_State *L);
-LUAI_FUNC void luaE_enterCcall (lua_State *L);
+LUAI_FUNC void luaE_checkcstack (lua_State *L);
+LUAI_FUNC void luaE_incCstack (lua_State *L);
 LUAI_FUNC void luaE_warning (lua_State *L, const char *msg, int tocont);
 LUAI_FUNC void luaE_warnerror (lua_State *L, const char *where);
 
 
-#define luaE_exitCcall(L)       ((L)->nCcalls++)
-
 #endif