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Fix preprocessor endless loop with no-op UDC replacements #1963

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Merged
RobertvanderHulst merged 2 commits into from
May 29, 2026
+56 −0
Merged

Fix preprocessor endless loop with no-op UDC replacements #1963

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Copilot May 29, 2026
a9b1fec
Fix preprocessor endless loop when UDC replacement produces identical…
Copilot May 29, 2026
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28 changes: 28 additions & 0 deletions src/Compiler/src/Compiler/XSharpCodeAnalysis/Preprocessor/XSharpPreprocessor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2620,7 +2620,15 @@ private bool doProcessTranslates(IList<XSharpToken> line, out IList<XSharpToken>
var rule = _transRules.FindMatchingRule(temp, out var matchInfo);
if (rule != null)
{
var prevTemp = temp;
temp = doReplace(temp, rule, matchInfo);
if (isResultUnchanged(prevTemp, temp))
{
// the replacement did not change the tokens, so stop to prevent an endless loop
result.AddRange(temp);
temp.Clear();
break;
}
if (usedRules.HasRecursion(rule, temp))
{
// duplicate, so exit now
Expand Down Expand Up @@ -2686,7 +2694,13 @@ private bool doProcessCommands(IList<XSharpToken> line, out IList<XSharpToken> r
// nothing to do, so exit. Leave changed the way it is. This does not have to be the first iteration
break;
}
var prevResult = result;
result = doReplace(result, rule, matchInfo);
if (isResultUnchanged(prevResult, result))
{
// the replacement did not change the tokens, so stop to prevent an endless loop
break;
}
if (usedRules.HasRecursion(rule, result))
{
// duplicate so exit now
Expand Down Expand Up @@ -2796,5 +2810,19 @@ private List<XSharpToken> doReplace(IList<XSharpToken> line, PPRule rule, PPMatc
#endif
return result;
}

private static bool isResultUnchanged(IList<XSharpToken> input, IList<XSharpToken> output)
{
if (input.Count != output.Count)
return false;
for (int i = 0; i < input.Count; i++)
{
if (!string.Equals(input[i].Text, output[i].Text, StringComparison.OrdinalIgnoreCase))
{
return false;
}
}
return true;
}
}
}
28 changes: 28 additions & 0 deletions src/Runtime/MacroCompiler/Preprocessor/XSharpPreprocessor.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -2540,7 +2540,15 @@ private bool doProcessTranslates(IList<XSharpToken> line, out IList<XSharpToken>
var rule = _transRules.FindMatchingRule(temp, out var matchInfo);
if (rule != null)
{
var prevTemp = temp;
temp = doReplace(temp, rule, matchInfo);
if (isResultUnchanged(prevTemp, temp))
{
// the replacement did not change the tokens, so stop to prevent an endless loop
result.AddRange(temp);
temp.Clear();
break;
}
if (usedRules.HasRecursion(rule, temp))
{
// duplicate, so exit now
Expand Down Expand Up @@ -2606,7 +2614,13 @@ private bool doProcessCommands(IList<XSharpToken> line, out IList<XSharpToken> r
// nothing to do, so exit. Leave changed the way it is. This does not have to be the first iteration
break;
}
var prevResult = result;
result = doReplace(result, rule, matchInfo);
if (isResultUnchanged(prevResult, result))
{
// the replacement did not change the tokens, so stop to prevent an endless loop
break;
}
if (usedRules.HasRecursion(rule, result))
{
// duplicate so exit now
Expand Down Expand Up @@ -2716,5 +2730,19 @@ private List<XSharpToken> doReplace(IList<XSharpToken> line, PPRule rule, PPMatc
#endif
return result;
}

private static bool isResultUnchanged(IList<XSharpToken> input, IList<XSharpToken> output)
{
if (input.Count != output.Count)
return false;
for (int i = 0; i < input.Count; i++)
{
if (!string.Equals(input[i].Text, output[i].Text, StringComparison.OrdinalIgnoreCase))
{
return false;
}
}
return true;
}
}
}