But the parameter types list are not the same. In one, compar is a pointer to a function with “C” language linkage, in the other one, it’s a pointer to a function with “C++” language linkage.
C++11, 7.5 specifies:
1 … Two function types with different language
linkages are distinct types even if they are otherwise identical.4 In a linkage-specification, the specified language linkage applies to the function
types of all function declarators, function names with external linkage, and variable names with external
linkage declared within the linkage-specification. [ Example:extern "C" void f1(void(*pf)(int)); // the name f1 and its function type have C language // linkage; pf is a pointer to a C function
The seeming inconsistency between 7.5/1 and 7.5/5 is solved when realising that 1 talks about function types, while 5 addresses function names.