Fix preprocessor endless loop with no-op UDC replacements#1963
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… output Add no-op detection in doProcessCommands() and doProcessTranslates() to break the processing loop when a UDC rule replacement produces tokens textually identical to its input. This prevents infinite loops with rules like `#xcommand NOTHING [<*any*>] => NOTHING` or `#xcommand ENDSEQUENCE [<*any*>] => ENDSEQUENCE` where the output matches the input pattern. Applied to both Compiler and MacroCompiler preprocessor implementations.
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[WIP] Fix endless loop caused by #xcommand NOTHING
Fix preprocessor endless loop with no-op UDC replacements
May 29, 2026
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RobertvanderHulst due to an error
May 29, 2026 16:24
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The preprocessor loops infinitely when a UDC rule's replacement is textually identical to its input, e.g.
#xcommand ENDSEQUENCE [<*any*>] => ENDSEQUENCE. The existingPPUsedRules.isDuplicate()recursion guard fails to catch this case.This also affects the XPP dialect's
ENDSEQUENCErule (XbasePPCmd.xh), triggered byBEGIN SEQUENCE / ENDSEQUENCE.Changes
isResultUnchanged()— compares token lists before/afterdoReplace()by count and text (case-insensitive)doProcessCommands()anddoProcessTranslates()now break immediately when the replacement produces identical output, before re-entering the matching loopCompilerandMacroCompilerpreprocessor implementations