From dbbe0f7971dfe89368224010352d2c08d13ef44f Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Tue, 7 Jul 2020 17:38:29 -0300
Subject: Fixed bug in 'checkstackp'

The macro 'checkstackp' can run a GC step and destroy a preallocated
CallInfo. It has been renamed to 'checkstackGCp' to hint of this
collateral effect.
---
 ldo.c | 13 +++++++------
 ldo.h |  4 +++-
 ltm.c |  4 ++--
 lvm.c |  2 +-
 4 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/ldo.c b/ldo.c
index c563b1d9..c4d8607b 100644
--- a/ldo.c
+++ b/ldo.c
@@ -466,13 +466,13 @@ void luaD_call (lua_State *L, StkId func, int nresults) {
       f = fvalue(s2v(func));
      Cfunc: {
       int n;  /* number of returns */
-      CallInfo *ci = next_ci(L);
-      checkstackp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
+      CallInfo *ci;
+      checkstackGCp(L, LUA_MINSTACK, func);  /* ensure minimum stack size */
+      L->ci = ci = next_ci(L);
       ci->nresults = nresults;
       ci->callstatus = CIST_C;
       ci->top = L->top + LUA_MINSTACK;
       ci->func = func;
-      L->ci = ci;
       lua_assert(ci->top <= L->stack_last);
       if (L->hookmask & LUA_MASKCALL) {
         int narg = cast_int(L->top - func) - 1;
@@ -486,12 +486,13 @@ void luaD_call (lua_State *L, StkId func, int nresults) {
       break;
     }
     case LUA_VLCL: {  /* Lua function */
-      CallInfo *ci = next_ci(L);
+      CallInfo *ci;
       Proto *p = clLvalue(s2v(func))->p;
       int narg = cast_int(L->top - func) - 1;  /* number of real arguments */
       int nfixparams = p->numparams;
       int fsize = p->maxstacksize;  /* frame size */
-      checkstackp(L, fsize, func);
+      checkstackGCp(L, fsize, func);
+      L->ci = ci = next_ci(L);
       ci->nresults = nresults;
       ci->u.l.savedpc = p->code;  /* starting point */
       ci->callstatus = 0;
@@ -505,7 +506,7 @@ void luaD_call (lua_State *L, StkId func, int nresults) {
       break;
     }
     default: {  /* not a function */
-      checkstackp(L, 1, func);  /* space for metamethod */
+      checkstackGCp(L, 1, func);  /* space for metamethod */
       luaD_tryfuncTM(L, func);  /* try to get '__call' metamethod */
       goto retry;  /* try again with metamethod */
     }
diff --git a/ldo.h b/ldo.h
index 821cb779..6c6cb285 100644
--- a/ldo.h
+++ b/ldo.h
@@ -17,6 +17,8 @@
 ** Macro to check stack size and grow stack if needed.  Parameters
 ** 'pre'/'pos' allow the macro to preserve a pointer into the
 ** stack across reallocations, doing the work only when needed.
+** It also allows the running of one GC step when the stack is
+** reallocated.
 ** 'condmovestack' is used in heavy tests to force a stack reallocation
 ** at every check.
 */
@@ -35,7 +37,7 @@
 
 
 /* macro to check stack size, preserving 'p' */
-#define checkstackp(L,n,p)  \
+#define checkstackGCp(L,n,p)  \
   luaD_checkstackaux(L, n, \
     ptrdiff_t t__ = savestack(L, p);  /* save 'p' */ \
     luaC_checkGC(L),  /* stack grow uses memory */ \
diff --git a/ltm.c b/ltm.c
index ae60983f..4770f96b 100644
--- a/ltm.c
+++ b/ltm.c
@@ -240,7 +240,7 @@ void luaT_adjustvarargs (lua_State *L, int nfixparams, CallInfo *ci,
   int actual = cast_int(L->top - ci->func) - 1;  /* number of arguments */
   int nextra = actual - nfixparams;  /* number of extra arguments */
   ci->u.l.nextraargs = nextra;
-  checkstackGC(L, p->maxstacksize + 1);
+  luaD_checkstack(L, p->maxstacksize + 1);
   /* copy function to the top of the stack */
   setobjs2s(L, L->top++, ci->func);
   /* move fixed parameters to the top of the stack */
@@ -259,7 +259,7 @@ void luaT_getvarargs (lua_State *L, CallInfo *ci, StkId where, int wanted) {
   int nextra = ci->u.l.nextraargs;
   if (wanted < 0) {
     wanted = nextra;  /* get all extra arguments available */
-    checkstackp(L, nextra, where);  /* ensure stack space */
+    checkstackGCp(L, nextra, where);  /* ensure stack space */
     L->top = where + nextra;  /* next instruction will need top */
   }
   for (i = 0; i < wanted && i < nextra; i++)
diff --git a/lvm.c b/lvm.c
index ccbfbab5..d78d6be2 100644
--- a/lvm.c
+++ b/lvm.c
@@ -1634,7 +1634,7 @@ void luaV_execute (lua_State *L, CallInfo *ci) {
         while (!ttisfunction(s2v(ra))) {  /* not a function? */
           luaD_tryfuncTM(L, ra);  /* try '__call' metamethod */
           b++;  /* there is now one extra argument */
-          checkstackp(L, 1, ra);
+          checkstackGCp(L, 1, ra);
         }
         if (!ttisLclosure(s2v(ra))) {  /* C function? */
           luaD_call(L, ra, LUA_MULTRET);  /* call it */
-- 
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