Maximum stack size may not fit in unsigned short

Therefore, fields ftransfer/ntransfer in lua_Debug must have type
'int'. (Maximum stack size must fit in an 'int'.) Also, this commit
adds check that maximum stack size respects size_t for size in bytes.

5 files changed, 46 insertions, 28 deletions

diff --git a/ldo.c b/ldo.c
index cd6dded6..34101ba3 100644
--- a/ldo.c
+++ b/ldo.c
@@ -171,6 +171,24 @@ int luaD_rawrunprotected (lua_State *L, Pfunc f, void *ud) {
 ** ===================================================================
 */
 
+/* some stack space for error handling */
+#define STACKERRSPACE   200
+
+
+/* maximum stack size that respects size_t */
+#define MAXSTACK_BYSIZET  ((MAX_SIZET / sizeof(StackValue)) - STACKERRSPACE)
+
+/*
+** Minimum between LUAI_MAXSTACK and MAXSTACK_BYSIZET
+** (Maximum size for the stack must respect size_t.)
+*/
+#define MAXSTACK        cast_int(LUAI_MAXSTACK < MAXSTACK_BYSIZET  \
+                                ? LUAI_MAXSTACK : MAXSTACK_BYSIZET)
+
+
+/* stack size with extra space for error handling */
+#define ERRORSTACKSIZE  (MAXSTACK + STACKERRSPACE)
+
 
 /*
 ** Change all pointers to the stack into offsets.
@@ -208,9 +226,6 @@ static void correctstack (lua_State *L) {
 }
 
 
-/* some space for error handling */
-#define ERRORSTACKSIZE  (LUAI_MAXSTACK + 200)
-
 /*
 ** Reallocate the stack to a new size, correcting all pointers into it.
 ** In ISO C, any pointer use after the pointer has been deallocated is
@@ -227,7 +242,7 @@ int luaD_reallocstack (lua_State *L, int newsize, int raiseerror) {
   int i;
   StkId newstack;
   int oldgcstop = G(L)->gcstopem;
-  lua_assert(newsize <= LUAI_MAXSTACK || newsize == ERRORSTACKSIZE);
+  lua_assert(newsize <= MAXSTACK || newsize == ERRORSTACKSIZE);
   relstack(L);  /* change pointers to offsets */
   G(L)->gcstopem = 1;  /* stop emergency collection */
   newstack = luaM_reallocvector(L, L->stack.p, oldsize + EXTRA_STACK,
@@ -254,7 +269,7 @@ int luaD_reallocstack (lua_State *L, int newsize, int raiseerror) {
 */
 int luaD_growstack (lua_State *L, int n, int raiseerror) {
   int size = stacksize(L);
-  if (l_unlikely(size > LUAI_MAXSTACK)) {
+  if (l_unlikely(size > MAXSTACK)) {
     /* if stack is larger than maximum, thread is already using the
        extra space reserved for errors, that is, thread is handling
        a stack error; cannot grow further than that. */
@@ -263,14 +278,14 @@ int luaD_growstack (lua_State *L, int n, int raiseerror) {
       luaD_throw(L, LUA_ERRERR);  /* error inside message handler */
     return 0;  /* if not 'raiseerror', just signal it */
   }
-  else if (n < LUAI_MAXSTACK) {  /* avoids arithmetic overflows */
+  else if (n < MAXSTACK) {  /* avoids arithmetic overflows */
     int newsize = 2 * size;  /* tentative new size */
     int needed = cast_int(L->top.p - L->stack.p) + n;
-    if (newsize > LUAI_MAXSTACK)  /* cannot cross the limit */
-      newsize = LUAI_MAXSTACK;
+    if (newsize > MAXSTACK)  /* cannot cross the limit */
+      newsize = MAXSTACK;
     if (newsize < needed)  /* but must respect what was asked for */
       newsize = needed;
-    if (l_likely(newsize <= LUAI_MAXSTACK))
+    if (l_likely(newsize <= MAXSTACK))
       return luaD_reallocstack(L, newsize, raiseerror);
   }
   /* else stack overflow */
@@ -306,17 +321,17 @@ static int stackinuse (lua_State *L) {
 ** to twice the current use. (So, the final stack size is at most 2/3 the
 ** previous size, and half of its entries are empty.)
 ** As a particular case, if stack was handling a stack overflow and now
-** it is not, 'max' (limited by LUAI_MAXSTACK) will be smaller than
+** it is not, 'max' (limited by MAXSTACK) will be smaller than
 ** stacksize (equal to ERRORSTACKSIZE in this case), and so the stack
 ** will be reduced to a "regular" size.
 */
 void luaD_shrinkstack (lua_State *L) {
   int inuse = stackinuse(L);
-  int max = (inuse > LUAI_MAXSTACK / 3) ? LUAI_MAXSTACK : inuse * 3;
+  int max = (inuse > MAXSTACK / 3) ? MAXSTACK : inuse * 3;
   /* if thread is currently not handling a stack overflow and its
      size is larger than maximum "reasonable" size, shrink it */
-  if (inuse <= LUAI_MAXSTACK && stacksize(L) > max) {
-    int nsize = (inuse > LUAI_MAXSTACK / 2) ? LUAI_MAXSTACK : inuse * 2;
+  if (inuse <= MAXSTACK && stacksize(L) > max) {
+    int nsize = (inuse > MAXSTACK / 2) ? MAXSTACK : inuse * 2;
     luaD_reallocstack(L, nsize, 0);  /* ok if that fails */
   }
   else  /* don't change stack */
@@ -408,7 +423,7 @@ static void rethook (lua_State *L, CallInfo *ci, int nres) {
         delta = ci->u.l.nextraargs + p->numparams + 1;
     }
     ci->func.p += delta;  /* if vararg, back to virtual 'func' */
-    ftransfer = cast(unsigned short, firstres - ci->func.p);
+    ftransfer = cast_int(firstres - ci->func.p);
     luaD_hook(L, LUA_HOOKRET, -1, ftransfer, nres);  /* call it */
     ci->func.p -= delta;
   }
diff --git a/lstate.h b/lstate.h
index 6094016d..e5056abe 100644
--- a/lstate.h
+++ b/lstate.h
@@ -207,8 +207,8 @@ struct CallInfo {
     int nyield;  /* number of values yielded */
     int nres;  /* number of values returned */
     struct {  /* info about transferred values (for call/return hooks) */
-      unsigned short ftransfer;  /* offset of first value transferred */
-      unsigned short ntransfer;  /* number of values transferred */
+      int ftransfer;  /* offset of first value transferred */
+      int ntransfer;  /* number of values transferred */
     } transferinfo;
   } u2;
   short nresults;  /* expected number of results from this function */
diff --git a/lua.h b/lua.h
index 2f9d0abb..dcf49264 100644
--- a/lua.h
+++ b/lua.h
@@ -503,8 +503,8 @@ struct lua_Debug {
   unsigned char nparams;/* (u) number of parameters */
   char isvararg;        /* (u) */
   char istailcall;      /* (t) */
-  unsigned short ftransfer;   /* (r) index of first value transferred */
-  unsigned short ntransfer;   /* (r) number of transferred values */
+  int ftransfer;   /* (r) index of first value transferred */
+  int ntransfer;   /* (r) number of transferred values */
   char short_src[LUA_IDSIZE]; /* (S) */
   /* private part */
   struct CallInfo *i_ci;  /* active function */
diff --git a/luaconf.h b/luaconf.h
index 65715c8b..80349acc 100644
--- a/luaconf.h
+++ b/luaconf.h
@@ -750,13 +750,13 @@
 @@ LUAI_MAXSTACK limits the size of the Lua stack.
 ** CHANGE it if you need a different limit. This limit is arbitrary;
 ** its only purpose is to stop Lua from consuming unlimited stack
-** space (and to reserve some numbers for pseudo-indices).
-** (It must fit into max(size_t)/32 and max(int)/2.)
+** space and to reserve some numbers for pseudo-indices.
+** (It must fit into max(int)/2.)
 */
-#if LUAI_IS32INT
+#if 1000000 < (INT_MAX / 2)
 #define LUAI_MAXSTACK           1000000
 #else
-#define LUAI_MAXSTACK           15000
+#define LUAI_MAXSTACK           (INT_MAX / 2u)
 #endif
 
 
diff --git a/manual/manual.of b/manual/manual.of
index 56619afe..1069f644 100644
--- a/manual/manual.of
+++ b/manual/manual.of
@@ -4262,8 +4262,9 @@ you push the main function plus any arguments
 onto the empty stack of the thread.
 then you call @Lid{lua_resume},
 with @id{nargs} being the number of arguments.
-This call returns when the coroutine suspends or finishes its execution.
-When it returns,
+The function returns when the coroutine suspends,
+finishes its execution, or raises an unprotected error.
+When it returns without errors,
 @id{*nresults} is updated and
 the top of the stack contains
 the @id{*nresults} values passed to @Lid{lua_yield}
@@ -4274,9 +4275,11 @@ or returned by the body function.
 without errors,
 or an error code in case of errors @see{statuscodes}.
 In case of errors,
-the error object is on the top of the stack.
+the error object is pushed on the top of the stack.
+(In that case, @id{nresults} is not updated,
+as its value would have to be 1 for the sole error object.)
 
-To resume a coroutine,
+To resume a suspended coroutine,
 you remove the @id{*nresults} yielded values from its stack,
 push the values to be passed as results from @id{yield},
 and then call @Lid{lua_resume}.
@@ -4822,8 +4825,8 @@ typedef struct lua_Debug {
   unsigned char nparams;      /* (u) number of parameters */
   char isvararg;              /* (u) */
   char istailcall;            /* (t) */
-  unsigned short ftransfer;   /* (r) index of first value transferred */
-  unsigned short ntransfer;   /* (r) number of transferred values */
+  int ftransfer;              /* (r) index of first value transferred */
+  int ntransfer;              /* (r) number of transferred values */
   char short_src[LUA_IDSIZE]; /* (S) */
   /* private part */
   @rep{other fields}