Changed signal of GC debt

Positive debts seems more natural then negative ones.

lapi.c

@@ -1168,8 +1168,8 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {
       g->gcstp = 0;  /* allow GC to run (bit GCSTPGC must be zero here) */
       if (todo == 0)
         todo = 1 << g->gcstepsize;  /* standard step size */
-      while (todo + g->GCdebt > 0) {  /* enough to run a step? */
-        todo += g->GCdebt;  /* decrement 'todo' (debt is usually negative) */
+      while (todo >= g->GCdebt) {  /* enough to run a step? */
+        todo -= g->GCdebt;  /* decrement 'todo' */
         luaC_step(L);  /* run one basic step */
         didsomething = 1;
         if (g->gckind == KGC_GEN)  /* minor collections? */
@@ -1177,8 +1177,8 @@ LUA_API int lua_gc (lua_State *L, int what, ...) {
         else if (g->gcstate == GCSpause)
           break;  /* don't run more than one cycle */
       }
-      /* add remaining 'todo' to total debt */
-      luaE_setdebt(g, todo + g->GCdebt);
+      /* remove remaining 'todo' from total debt */
+      luaE_setdebt(g, g->GCdebt - todo);
       g->gcstp = oldstp;  /* restore previous state */
       if (didsomething && g->gcstate == GCSpause)  /* end of cycle? */
         res = 1;  /* signal it */

lgc.c

@@ -242,7 +242,7 @@ GCObject *luaC_newobjdt (lua_State *L, int tt, size_t sz, size_t offset) {
   global_State *g = G(L);
   char *p = cast_charp(luaM_newobject(L, novariant(tt), sz));
   GCObject *o = cast(GCObject *, p + offset);
-  g->GCdebt++;
+  g->GCdebt--;
   o->marked = luaC_white(g);
   o->tt = tt;
   o->next = g->allgc;
@@ -1034,8 +1034,8 @@ void luaC_checkfinalizer (lua_State *L, GCObject *o, Table *mt) {
 */
 static void setpause (global_State *g) {
   l_obj threshold = applygcparam(g, gcpause, g->marked);
-  l_obj debt = gettotalobjs(g) - threshold;
-  if (debt > 0) debt = 0;
+  l_obj debt = threshold - gettotalobjs(g);
+  if (debt < 0) debt = 0;
   luaE_setdebt(g, debt);
 }
 
@@ -1285,7 +1285,7 @@ static void atomic2gen (lua_State *L, global_State *g) {
 ** total number of objects grows 'genminormul'%.
 */
 static void setminordebt (global_State *g) {
-  luaE_setdebt(g, -applygcparam(g, genminormul, gettotalobjs(g)));
+  luaE_setdebt(g, applygcparam(g, genminormul, gettotalobjs(g)));
 }
 
 
@@ -1378,13 +1378,13 @@ static void genmajorstep (lua_State *L, global_State *g) {
 ** Does a generational "step".  If the total number of objects grew
 ** more than 'majormul'% since the last major collection, does a
 ** major collection.  Otherwise, does a minor collection.  The test
-** ('GCdebt' > 0) avoids major collections when the step originated from
+** ('GCdebt' != 0) avoids major collections when the step originated from
 ** 'collectgarbage("step")'.
 */
 static void genstep (lua_State *L, global_State *g) {
   l_obj majorbase = g->GClastmajor;  /* count after last major collection */
   l_obj majorinc = applygcparam(g, genmajormul, majorbase);
-  if (g->GCdebt > 0 && gettotalobjs(g) > majorbase + majorinc) {
+  if (g->GCdebt != 0 && gettotalobjs(g) > majorbase + majorinc) {
     /* do a major collection */
     enterinc(g);
     g->gckind = KGC_GENMAJOR;
@@ -1605,7 +1605,7 @@ static void incstep (lua_State *L, global_State *g) {
   if (g->gcstate == GCSpause)
     setpause(g);  /* pause until next cycle */
   else {
-    luaE_setdebt(g, -stepsize);
+    luaE_setdebt(g, stepsize);
   }
 }
 
@@ -1618,7 +1618,7 @@ void luaC_step (lua_State *L) {
   global_State *g = G(L);
   lua_assert(!g->gcemergency);
   if (!gcrunning(g))  /* not running? */
-    luaE_setdebt(g, -2000);
+    luaE_setdebt(g, 2000);
   else {
     switch (g->gckind) {
       case KGC_INC:

lgc.h

@@ -175,13 +175,13 @@
 
 
 /*
-** Does one step of collection when debt becomes positive. 'pre'/'pos'
+** Does one step of collection when debt becomes zero. 'pre'/'pos'
 ** allows some adjustments to be done only when needed. macro
 ** 'condchangemem' is used only for heavy tests (forcing a full
 ** GC cycle on every opportunity)
 */
 #define luaC_condGC(L,pre,pos) \
-	{ if (G(L)->GCdebt > 0) { pre; luaC_step(L); pos;}; \
+	{ if (G(L)->GCdebt <= 0) { pre; luaC_step(L); pos;}; \
 	  condchangemem(L,pre,pos); }
 
 /* more often than not, 'pre'/'pos' are empty */

llimits.h

@@ -33,6 +33,8 @@ typedef unsigned long lu_mem;
 typedef long l_obj;
 #endif				/* } */
 
+#define MAX_LOBJ	cast(l_obj, ~cast(lu_mem, 0) >> 1)
+
 
 /* chars used as small naturals (so that 'char' is reserved for characters) */
 typedef unsigned char lu_byte;
@@ -47,11 +49,6 @@ typedef signed char ls_byte;
                           : (size_t)(LUA_MAXINTEGER))
 
 
-#define MAX_LUMEM	((lu_mem)(~(lu_mem)0))
-
-#define MAX_LMEM	((l_obj)(MAX_LUMEM >> 1))
-
-
 #define MAX_INT		INT_MAX  /* maximum value of an int */
 
 

lstate.c

@@ -89,9 +89,9 @@ static unsigned int luai_makeseed (lua_State *L) {
 void luaE_setdebt (global_State *g, l_obj debt) {
   l_obj tb = gettotalobjs(g);
   lua_assert(tb > 0);
-  if (debt < tb - MAX_LMEM)
-    debt = tb - MAX_LMEM;  /* will make 'totalobjs == MAX_LMEM' */
-  g->totalobjs = tb - debt;
+  if (debt > MAX_LOBJ - tb)
+    debt = MAX_LOBJ - tb;  /* will make 'totalobjs == MAX_LMEM' */
+  g->totalobjs = tb + debt;
   g->GCdebt = debt;
 }
 

lstate.h

@@ -251,8 +251,8 @@ typedef struct global_State {
   lua_Alloc frealloc;  /* function to reallocate memory */
   void *ud;         /* auxiliary data to 'frealloc' */
   lu_mem totalbytes;  /* number of bytes currently allocated */
-  l_obj totalobjs;  /* total number of objects allocated - GCdebt */
-  l_obj GCdebt;  /* bytes allocated not yet compensated by the collector */
+  l_obj totalobjs;  /* total number of objects allocated + GCdebt */
+  l_obj GCdebt;  /* objects counted but not yet allocated */
   l_obj marked;  /* number of objects marked in a GC cycle */
   l_obj GClastmajor;  /* objects at last major collection */
   stringtable strt;  /* hash table for strings */
@@ -388,7 +388,7 @@ union GCUnion {
 
 
 /* actual number of total objects allocated */
-#define gettotalobjs(g)	((g)->totalobjs + (g)->GCdebt)
+#define gettotalobjs(g)	((g)->totalobjs - (g)->GCdebt)
 
 
 LUAI_FUNC void luaE_setdebt (global_State *g, l_obj debt);