System.Xml.CharCheckingReaderTests fails with OutOfMemoryException

[jkotas]

Build Information

Build: https://dev.azure.com/dnceng-public/cbb18261-c48f-4abb-8651-8cdcb5474649/_build/results?buildId=1149008
Build error leg or test failing: System.Xml.CharCheckingReaderTests.CharCheckingReaderTest.RunTests
Pull request: #119599

Error Message

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": ["System.Xml.CharCheckingReaderTests","OutOfMemoryException"],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1149008
Error message validated: [System.Xml.CharCheckingReaderTests OutOfMemoryException]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 9/16/2025 6:43:18 AM UTC

Report

Build	Definition	Test	Pull Request
1224229	dotnet/runtime	System.Xml.CharCheckingReaderTests.CharCheckingReaderTest.RunTests	#122243
1224071	dotnet/runtime	System.Xml.CharCheckingReaderTests.CharCheckingReaderTest.RunTests	#122209
1217113	dotnet/runtime	System.Xml.CharCheckingReaderTests.CharCheckingReaderTest.RunTests	#122088
1216392	dotnet/runtime	System.Xml.CharCheckingReaderTests.CharCheckingReaderTest.RunTests	#122072
1205802	dotnet/runtime	System.Xml.CharCheckingReaderTests.CharCheckingReaderTest.RunTests	#121373

Summary

24-Hour Hit Count	7-Day Hit Count	1-Month Count
0	2	5

[jkotas]

  Starting:    System.Private.Xml.Tests (parallel test collections = on [4 threads], stop on fail = off)
    System.Xml.CharCheckingReaderTests.CharCheckingReaderTest.RunTests(testCase: ReadBinHex runs into an Overflow) [FAIL]
      System.OutOfMemoryException : Exception of type 'System.OutOfMemoryException' was thrown.
      Stack Trace:
        /_/src/libraries/System.Private.CoreLib/src/System/String.cs(316,0): at System.String.Ctor(ReadOnlySpan`1 value)
        /_/src/libraries/System.Private.CoreLib/src/System/Span.cs(382,0): at System.Span`1.ToString()
        /_/src/libraries/System.Private.CoreLib/src/System/String.Manipulation.cs(544,0): at System.String.FormatHelper(IFormatProvider provider, String format, ReadOnlySpan`1 args)
        /_/src/libraries/System.Private.CoreLib/src/System/String.Manipulation.cs(492,0): at System.String.Format(String format, ReadOnlySpan`1 args)
        /_/src/libraries/System.Private.Xml/src/System/Xml/XmlException.cs(202,0): at System.Xml.XmlException.CreateMessage(String res, String[] args, Int32 lineNumber, Int32 linePosition)
        /_/src/libraries/System.Private.Xml/src/System/Xml/XmlException.cs(167,0): at System.Xml.XmlException..ctor(String res, String[] args, Exception innerException, Int32 lineNumber, Int32 linePosition, String sourceUri)
        /_/src/libraries/System.Private.Xml/src/System/Xml/XmlException.cs(122,0): at System.Xml.XmlException..ctor(String res, String arg)
        /_/src/libraries/System.Private.Xml/src/System/Xml/BinHexDecoder.cs(165,0): at System.Xml.BinHexDecoder.Decode(ReadOnlySpan`1 chars, Span`1 bytes, Boolean& hasHalfByteCached, Byte& cachedHalfByte, Int32& charsDecoded, Int32& bytesDecoded)
        /_/src/libraries/System.Private.Xml/src/System/Xml/BinHexDecoder.cs(74,0): at System.Xml.BinHexDecoder.Decode(String str, Int32 startPos, Int32 len)
        /_/src/libraries/System.Private.Xml/src/System/Xml/Core/ReadContentAsBinaryHelper.cs(367,0): at System.Xml.ReadContentAsBinaryHelper.ReadContentAsBinary(Byte[] buffer, Int32 index, Int32 count)
        /_/src/libraries/System.Private.Xml/src/System/Xml/Core/ReadContentAsBinaryHelper.cs(394,0): at System.Xml.ReadContentAsBinaryHelper.ReadElementContentAsBinary(Byte[] buffer, Int32 index, Int32 count)
        /_/src/libraries/System.Private.Xml/src/System/Xml/Core/ReadContentAsBinaryHelper.cs(232,0): at System.Xml.ReadContentAsBinaryHelper.ReadElementContentAsBinHex(Byte[] buffer, Int32 index, Int32 count)
        /_/src/libraries/System.Private.Xml/src/System/Xml/Core/XmlCharCheckingReader.cs(567,0): at System.Xml.XmlCharCheckingReader.ReadElementContentAsBinHex(Byte[] buffer, Int32 index, Int32 count)
        /_/src/libraries/System.Private.Xml/tests/XmlReaderLib/CDataReader.cs(822,0): at System.Xml.Tests.CDataReader.ReadElementContentAsBinHex(Byte[] array, Int32 offset, Int32 len)
        /_/src/libraries/System.Private.Xml/tests/XmlReaderLib/ReadBinHex.cs(970,0): at System.Xml.Tests.TCReadElementContentAsBinHex.TestReadBinHex_105376()
        /_/src/libraries/Common/tests/System/Xml/ModuleCore/cvariation.cs(76,0): at OLEDB.Test.ModuleCore.CVariation.Execute()
        /_/src/libraries/Common/tests/System/Xml/ModuleCore/ctestcase.cs(131,0): at OLEDB.Test.ModuleCore.CTestCase.<>c__DisplayClass7_1.<TestCases>b__0()
        /_/src/libraries/Common/tests/System/Xml/ModuleCore/XunitTestCase.cs(33,0): at OLEDB.Test.ModuleCore.XunitTestCase.Run()

[jkotas]

This is failing on other PRs as well (e.g. #119739), so it does not appear to be issue introduced by #119599

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