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Fix for(;;) NullReferenceException in parser #113

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Merged
praeclarum merged 3 commits into from
Mar 31, 2026
Merged

Fix for(;;) NullReferenceException in parser #113

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a882b74
Initial plan
Copilot Mar 31, 2026
82d14b0
Fix for(;;) NullReferenceException: handle null expression_statement …
Copilot Mar 31, 2026
43fd50f
Simplify null checks to use 'as' with null-conditional operator
Copilot Mar 31, 2026
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8 changes: 4 additions & 4 deletions CLanguage/Parser/CParser.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -1825,25 +1825,25 @@ internal Object yyparse (yyParser.yyInput yyLex)
case 292:
#line 1115 "CParser.jay"
{
yyVal = new ForStatement((Statement)yyVals[-3+yyTop], ((ExpressionStatement)yyVals[-2+yyTop]).Expression, ((Statement)yyVals[0+yyTop]).ToBlock ());
yyVal = new ForStatement((Statement)yyVals[-3+yyTop], (yyVals[-2+yyTop] as ExpressionStatement)?.Expression, ((Statement)yyVals[0+yyTop]).ToBlock ());
}
break;
case 293:
#line 1119 "CParser.jay"
{
yyVal = new ForStatement((Statement)yyVals[-4+yyTop], ((ExpressionStatement)yyVals[-3+yyTop]).Expression, (Expression)yyVals[-2+yyTop], ((Statement)yyVals[0+yyTop]).ToBlock ());
yyVal = new ForStatement((Statement)yyVals[-4+yyTop], (yyVals[-3+yyTop] as ExpressionStatement)?.Expression, (Expression)yyVals[-2+yyTop], ((Statement)yyVals[0+yyTop]).ToBlock ());
}
break;
case 294:
#line 1123 "CParser.jay"
{
yyVal = new ForStatement((Statement)yyVals[-3+yyTop], ((ExpressionStatement)yyVals[-2+yyTop]).Expression, ((Statement)yyVals[0+yyTop]).ToBlock ());
yyVal = new ForStatement((Statement)yyVals[-3+yyTop], (yyVals[-2+yyTop] as ExpressionStatement)?.Expression, ((Statement)yyVals[0+yyTop]).ToBlock ());
}
break;
case 295:
#line 1127 "CParser.jay"
{
yyVal = new ForStatement((Statement)yyVals[-4+yyTop], ((ExpressionStatement)yyVals[-3+yyTop]).Expression, (Expression)yyVals[-2+yyTop], ((Statement)yyVals[0+yyTop]).ToBlock ());
yyVal = new ForStatement((Statement)yyVals[-4+yyTop], (yyVals[-3+yyTop] as ExpressionStatement)?.Expression, (Expression)yyVals[-2+yyTop], ((Statement)yyVals[0+yyTop]).ToBlock ());
}
break;
case 297:
Expand Down
8 changes: 4 additions & 4 deletions CLanguage/Parser/CParser.jay
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Expand Up @@ -1111,19 +1111,19 @@ iteration_statement
}
| FOR '(' expression_statement expression_statement ')' statement
{
$$ = new ForStatement((Statement)$3, ((ExpressionStatement)$4).Expression, ((Statement)$6).ToBlock ());
$$ = new ForStatement((Statement)$3, ($4 as ExpressionStatement)?.Expression, ((Statement)$6).ToBlock ());
}
| FOR '(' expression_statement expression_statement expression ')' statement
{
$$ = new ForStatement((Statement)$3, ((ExpressionStatement)$4).Expression, (Expression)$5, ((Statement)$7).ToBlock ());
$$ = new ForStatement((Statement)$3, ($4 as ExpressionStatement)?.Expression, (Expression)$5, ((Statement)$7).ToBlock ());
}
| FOR '(' declaration expression_statement ')' statement
{
$$ = new ForStatement((Statement)$3, ((ExpressionStatement)$4).Expression, ((Statement)$6).ToBlock ());
$$ = new ForStatement((Statement)$3, ($4 as ExpressionStatement)?.Expression, ((Statement)$6).ToBlock ());
}
| FOR '(' declaration expression_statement expression ')' statement
{
$$ = new ForStatement((Statement)$3, ((ExpressionStatement)$4).Expression, (Expression)$5, ((Statement)$7).ToBlock ());
$$ = new ForStatement((Statement)$3, ($4 as ExpressionStatement)?.Expression, (Expression)$5, ((Statement)$7).ToBlock ());
}
;

Expand Down
14 changes: 8 additions & 6 deletions CLanguage/Syntax/ForStatement.cs
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Expand Up @@ -11,11 +11,11 @@ namespace CLanguage.Syntax
public class ForStatement : Statement
{
public Block InitBlock { get; private set; }
public Expression ContinueExpression { get; private set; }
public Expression? ContinueExpression { get; private set; }
public Expression? NextExpression { get; private set; }
public Block LoopBody { get; private set; }

public ForStatement (Statement initStatement, Expression continueExpr, Block body)
public ForStatement (Statement initStatement, Expression? continueExpr, Block body)
{
InitBlock = new Block (VariableScope.Local);
if (initStatement != null) {
Expand All @@ -25,7 +25,7 @@ public ForStatement (Statement initStatement, Expression continueExpr, Block bod
LoopBody = body;
}

public ForStatement (Statement initStatement, Expression continueExpr, Expression nextExpr, Block body)
public ForStatement (Statement initStatement, Expression? continueExpr, Expression nextExpr, Block body)
{
InitBlock = new Block (VariableScope.Local);
if (initStatement != null) {
Expand Down Expand Up @@ -63,9 +63,11 @@ protected override void DoEmit (EmitContext initialContext)
//
var conditionLabel = ec.DefineLabel ();
ec.EmitLabel (conditionLabel);
ContinueExpression.Emit (ec);
ec.EmitCastToBoolean (ContinueExpression.GetEvaluatedCType (ec));
ec.Emit (OpCode.BranchIfFalse, endLabel);
if (ContinueExpression != null) {
ContinueExpression.Emit (ec);
ec.EmitCastToBoolean (ContinueExpression.GetEvaluatedCType (ec));
ec.Emit (OpCode.BranchIfFalse, endLabel);
}

//
// Fall through to the loop body
Expand Down
52 changes: 52 additions & 0 deletions CLanguageTests/InterpreterTests.cs
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Expand Up @@ -36,11 +36,11 @@
Assert.IsTrue (hit[0]);
Assert.IsFalse (hit[1]);
Assert.IsFalse (hit[2]);
it.Step ();

Check warning on line 39 in CLanguageTests/InterpreterTests.cs

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'CInterpreter.Step()' is obsolete: 'Please use Run() which Steps for 1 machine second.'
Assert.IsTrue (hit[0]);
Assert.IsTrue (hit[1]);
Assert.IsFalse (hit[2]);
it.Step ();

Check warning on line 43 in CLanguageTests/InterpreterTests.cs

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GitHub Actions / build 

'CInterpreter.Step()' is obsolete: 'Please use Run() which Steps for 1 machine second.'
Assert.IsTrue (hit[0]);
Assert.IsTrue (hit[1]);
Assert.IsTrue (hit[2]);
Expand Down Expand Up @@ -246,6 +246,58 @@
}");
}

[TestMethod]
public void ForLoopInfinite ()
{
Run (@"
void main () {
int i = 0;
for (;;) {
i++;
if (i >= 10) break;
}
assertAreEqual (10, i);
}");
}

[TestMethod]
public void ForLoopEmptyCondition ()
{
Run (@"
void main () {
int i;
for (i = 0; ; i++) {
if (i >= 5) break;
}
assertAreEqual (5, i);
}");
}

[TestMethod]
public void ForLoopEmptyIncrement ()
{
Run (@"
void main () {
int i;
for (i = 0; i < 10;) {
i++;
}
assertAreEqual (10, i);
}");
}

[TestMethod]
public void ForLoopEmptyInit ()
{
Run (@"
void main () {
int i = 0;
for (; i < 5; i++) {
}
assertAreEqual (5, i);
}");
}

[TestMethod]
public void WhileLoopWithBreak ()
{
Expand Down
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