ALM used Azure DevOps CI system used Azure DevOps Scanner command used when applicable (private details masked) 4.1.0, build-wrapper, mixed solution Languages of the repository Visual Studio 2026: C++23, C# Error observed: Specialization of std::hash for user-defined type is reported as an issue. …

Hi @milbrandt , Thank you for the reproducer, it allowed me to understand the situation: In your code, the std namespace does not only contain the specialization for std::hash (which is fine), but also a using directive. Since a using directive is a declaration, it is undefined behavior, which is w…

Hi @milbrandt , I tried to reproduce your issue, with the following compilable code (extracted from yours): #include <unordered_map> class OperationInfo {}; namespace std { template<> struct hash<OperationInfo> { std::size_t operator()(const OperationInfo& ) const noexcept …

Hi @JolyLoic I will try to reduce the solution and reproduce it in a smaller context. As a workaround I removed namespace std and implement it with fully quallified names (avoid ADL). Then no longer S3470 was reported. We use Visual Studio 2026 but still toolset v143. template<> struct std::hash<…

Yes, we plan to add an example in the rule description that uses this form, because we think it is more convenient that opening the std namespace.

Hi @JolyLoic , I now reduced everything to a single file. In Visual Studio, the error list is empty, but in SonarCloud still the S3470 is reported. Generating reproducer file failed. ##[error]12:54:35.97 ERROR: The sonar.cfamily.reproducer property was set but no matching file was found. The pr…

You should write the path exactly as it appears in the log, in this case, with forward slashes: [image] Volker Milbrandt: D:/_1/35/s/source/WT.NXG.ComputeEngines/AbstractionsDataTypes.ixx It is expected that this rule does not raise in SonarQube for IDE: It is system level, and means nothing…

I’ll try it tomorrow - and I have to force for a specific build agent. The number in the path D:_1\7\s depends on the build agent and therefore in the build definition is always used $(Build.SourcesDirectory). But this would be another topic.

Good morning @JolyLoic , finally the reproducer file was created. I renamed the extension as tarx.xz is blocked for uploading. sonar-cfamily-reproducer.tarxz (907.6 KB) I will open another thread regarding generating reproducer files.

Thanks @JolyLoic for the C++ lesson. I have to admit, I didn’t took that into account based on the message and description “Why is this an issue?” While reviewing, it was only a shortcut to avoid writing the fully qualified names of the user defined types.

I did not really know it either 5 minutes before I answered you :slight_smile:

cpp:S3470 for overloading std::hash

SonarQube Cloud

ganncamp (G Ann Campbell) February 26, 2026, 12:43pm 12

Hi,

On a side note, you’re the second person this week to struggle with the upload. I’ve (finally!) authorized uploads of .xz.

Ann

Problems generating reproducer files

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C++ fully specialized templates seen as variable SonarQube Server / Community Build sonarqube , cfamily , bug	10	679	December 1, 2022
Sonar Scanner fails with 9.9 if operator== is implemented in cpp file SonarQube Server / Community Build scanner , cfamily	5	414	March 13, 2023
More rules to write C++17 compliant code Sonar Updates cfamily , security	0	827	January 15, 2021
False Positive for catching type inheriting from std::exception in templates Report False-positive / False-negative... cfamily	5	624	September 19, 2022
False positive on shuffle Rules and Languages cfamily	8	70	February 11, 2026

cpp:S3470 for overloading std::hash

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