Fix a crash when using a constant global variable (created via MakeConstantGlobal, such as IsHPCGAP) as index variable of a for loop

src/code.c

@@ -1086,12 +1086,6 @@ void CodeForBegin ( void )
 
 void CodeForIn ( void )
 {
- Expr var = PopExpr();
- if (TNUM_EXPR(var) == EXPR_REF_GVAR)
- {
- PushGlobalForLoopVariable(READ_EXPR(var, 0));
- }
- PushExpr(var);
 }
 
 void CodeForBeginBody ( void )
@@ -1112,9 +1106,6 @@ void CodeForEndBody (
  /* get the variable reference */
  var = PopExpr();
 
- if (TNUM_EXPR(var) == EXPR_REF_GVAR)
- PopGlobalForLoopVariable();
-
  /* select the type of the for-statement */
  if ( TNUM_EXPR(list) == EXPR_RANGE && SIZE_EXPR(list) == 2*sizeof(Expr)
  && IS_REF_LVAR(var) ) {

src/read.c

@@ -105,28 +105,29 @@ static void ReadFuncExprAbbrevSingle(ScannerState * s, TypSymbolSet follow);
 
 static void ReadAtom(ScannerState * s, TypSymbolSet follow, Char mode);
 
-void PushGlobalForLoopVariable( UInt var)
+static void PushGlobalForLoopVariable(UInt var)
 {
  struct ReaderState * rs = ReaderState();
- if (rs->CurrentGlobalForLoopDepth < 100)
+ if (rs->CurrentGlobalForLoopDepth <
+ ARRAY_SIZE(rs->CurrentGlobalForLoopVariables))
  rs->CurrentGlobalForLoopVariables[rs->CurrentGlobalForLoopDepth] = var;
  rs->CurrentGlobalForLoopDepth++;
 }
 
-void PopGlobalForLoopVariable( void )
+static void PopGlobalForLoopVariable(void)
 {
  GAP_ASSERT(ReaderState()->CurrentGlobalForLoopDepth);
  ReaderState()->CurrentGlobalForLoopDepth--;
 }
 
-static UInt GlobalComesFromEnclosingForLoop (UInt var)
+static UInt GlobalComesFromEnclosingForLoop(UInt var)
 {
  struct ReaderState * rs = ReaderState();
  for (UInt i = 0; i < rs->CurrentGlobalForLoopDepth; i++) {
- if (i == 100)
- return 0;
+ if (i == ARRAY_SIZE(rs->CurrentGlobalForLoopVariables))
+  return 0;
  if (rs->CurrentGlobalForLoopVariables[i] == var)
- return 1;
+  return 1;
  }
  return 0;
 }
@@ -2050,7 +2051,9 @@ static void ReadFor(ScannerState * s, TypSymbolSet follow)
  Match(s, S_FOR, "for", follow);
 
  /* <Var> */
- ReadCallVarAss(s, follow, 'r');
+ volatile LHSRef ref = ReadVar(s, follow);
+ if (ref.type != R_INVALID)
+ EvalRef(ref, 1);
 
  /* 'in' <Expr> */
  Match(s, S_IN, "in", S_DO|S_OD|follow);
@@ -2059,11 +2062,15 @@ static void ReadFor(ScannerState * s, TypSymbolSet follow)
 
  /* 'do' <Statements> */
  Match(s, S_DO, "do", STATBEGIN|S_OD|follow);
+ if (ref.type == R_GVAR)
+ PushGlobalForLoopVariable(ref.var);
  ReaderState()->LoopNesting++;
  TRY_IF_NO_ERROR { IntrForBeginBody(); }
  nrs = ReadStats(s, S_OD|follow);
  TRY_IF_NO_ERROR { IntrForEndBody( nrs ); }
  ReaderState()->LoopNesting--;
+ if (ref.type == R_GVAR)
+ PopGlobalForLoopVariable();
 
  /* 'od' */
  Match(s, S_OD, "while parsing a 'for' loop: statement or 'od'", follow);

src/read.h

@@ -116,14 +116,6 @@ void StartFakeFuncExpr(Int startLine);
 void FinishAndCallFakeFuncExpr(void);
 
 
-/****************************************************************************
-**
-*/
-void PushGlobalForLoopVariable(UInt var);
-
-void PopGlobalForLoopVariable(void);
-
-
 /****************************************************************************
 **
 *F Call0ArgsInNewReader(Obj f) . . . . . . . . . . . . call a GAP function

tst/testinstall/coder.tst

@@ -300,5 +300,41 @@ gap> function() Unbind(l![fail]); end();
 Error, PosObj Assignment: <position> must be a positive small integer (not the\
  value 'fail')
 
+#
+# weird corner cases in for loop index variables
+#
+gap> function() for + in [1,2,3] do od; end();
+Syntax error: Identifier expected in stream:1
+function() for + in [1,2,3] do od; end();
+ ^
+gap> function() local x; for x[1] in [1,2,3] do od; end();
+Syntax error: in expected in stream:1
+function() local x; for x[1] in [1,2,3] do od; end();
+ ^
+gap> function() local x; for x{[1]} in [1,2,3] do od; end();
+Syntax error: in expected in stream:1
+function() local x; for x{[1]} in [1,2,3] do od; end();
+ ^
+gap> function() for IsHPCGAP in [1,2,3] do od; end();
+Error, Variable: 'IsHPCGAP' is constant
+gap> function() for IsHPCGAP[1] in [1,2,3] do od; end();
+Syntax error: in expected in stream:1
+function() for IsHPCGAP[1] in [1,2,3] do od; end();
+ ^
+gap> function() for IsHPCGAP{[1]} in [1,2,3] do od; end();
+Syntax error: in expected in stream:1
+function() for IsHPCGAP{[1]} in [1,2,3] do od; end();
+ ^
+gap> function() for PrintObj in [1,2,3] do od; end();
+Error, Variable: 'PrintObj' is read only
+gap> function() for PrintObj[1] in [1,2,3] do od; end();
+Syntax error: in expected in stream:1
+function() for PrintObj[1] in [1,2,3] do od; end();
+ ^
+gap> function() for PrintObj{[1]} in [1,2,3] do od; end();
+Syntax error: in expected in stream:1
+function() for PrintObj{[1]} in [1,2,3] do od; end();
+ ^
+
 #
 gap> STOP_TEST("coder.tst", 1);

tst/testinstall/interpreter.tst

@@ -252,6 +252,42 @@ gap> Unbind(l![fail]);
 Error, PosObj Assignment: <position> must be a positive small integer (not the\
  value 'fail')
 
+#
+# weird corner cases in for loop index variables
+#
+gap> for + in [1,2,3] do od;
+Syntax error: Identifier expected in stream:1
+for + in [1,2,3] do od;
+ ^
+gap> for x[1] in [1,2,3] do od;
+Syntax error: in expected in stream:1
+for x[1] in [1,2,3] do od;
+ ^
+gap> for x{[1]} in [1,2,3] do od;
+Syntax error: in expected in stream:1
+for x{[1]} in [1,2,3] do od;
+ ^
+gap> for IsHPCGAP in [1,2,3] do od;
+Error, Variable: 'IsHPCGAP' is constant
+gap> for IsHPCGAP[1] in [1,2,3] do od;
+Syntax error: in expected in stream:1
+for IsHPCGAP[1] in [1,2,3] do od;
+ ^
+gap> for IsHPCGAP{[1]} in [1,2,3] do od;
+Syntax error: in expected in stream:1
+for IsHPCGAP{[1]} in [1,2,3] do od;
+ ^
+gap> for PrintObj in [1,2,3] do od;
+Error, Variable: 'PrintObj' is read only
+gap> for PrintObj[1] in [1,2,3] do od;
+Syntax error: in expected in stream:1
+for PrintObj[1] in [1,2,3] do od;
+ ^
+gap> for PrintObj{[1]} in [1,2,3] do od;
+Syntax error: in expected in stream:1
+for PrintObj{[1]} in [1,2,3] do od;
+ ^
+
 #
 #
 gap> STOP_TEST("interpreter.tst", 1);