Why Does GCC Fail to Compile Explicit Specialization in Non-Namespace Scope?

Explicit Specialization in Non-Namespace Scope

The given code fails to compile in GCC despite compiling successfully in Clang. According to the C standard ([temp.expl.spec]), explicit specializations can be declared in any scope where the corresponding primary template could be defined.

This behavior appears to be a bug in GCC. According to CWG 727, the rule in [temp.expl.spec] regarding explicit specialization has been modified to allow such declarations in any relevant scope.

Scope of Explicit Specialization

The original standard stated that explicit specialization should be declared in a namespace enclosing the specialized template. However, the current standard permits explicit specialization in any scope where the primary template can be defined:

• Class definitions (12.2)
• Member functions (17.6.2)
• Inline namespaces (10.3.1.2)

GCC's failure to adhere to this updated rule constitutes a bug. The issue has been identified as Bug 85282 and is currently tracked by the GCC development team.

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