Anonymous namespace implies internal linkage for its members.
When it is defined in a header, then each translation unit,
which includes such header defines its own unique instance
of members of the unnamed namespace that are ODR-used within
that translation unit.
This can lead to unexpected results including code bloat
or undefined behavior due to ODR violations.
This PR removes unnamed namespaces from header files.
References:
- [CppCoreGuidelines: "SF.21: Don’t use an unnamed (anonymous) namespace in a header"](https://isocpp.github.io/CppCoreGuidelines/CppCoreGuidelines#sf21-dont-use-an-unnamed-anonymous-namespace-in-a-header)
- [SEI CERT C++: "DCL59-CPP. Do not define an unnamed namespace in a header file"](https://wiki.sei.cmu.edu/confluence/display/cplusplus/DCL59-CPP.+Do+not+define+an+unnamed+namespace+in+a+header+file)
Closesscylladb/scylladb#16998
* github.com:scylladb/scylladb:
utils/config_file_impl.hh: remove anonymous namespace from header
mutation/mutation.hh: remove anonymous namespace from header
c6fd4dffbb