extern “C” linkage inside C++ namespace?

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Your code works, but you should beware that all functions that have extern "C" linkage share the same space of names, but that is not to be confused with the C++ notion of “namespace”: Your function is really someNameSpace::doSomething, but you cannot have any other extern "C" function with unqualified name doSomething in any other namespace.

See 7.5/6:

At most one function with a particular name can have C language linkage. Two declarations for a function
with C language linkage with the same function name (ignoring the namespace names that qualify it) that
appear in different namespace scopes refer to the same function. Two declarations for a variable with C
language linkage with the same name (ignoring the namespace names that qualify it) that appear in different
namespace scopes refer to the same variable. An entity with C language linkage shall not be declared with
the same name as a variable in global scope, unless both declarations denote the same entity; no diagnostic is
required if the declarations appear in different translation units. A variable with C language linkage shall not
be declared with the same name as a function with C language linkage (ignoring the namespace names that
qualify the respective names); no diagnostic is required if the declarations appear in different translation
units. [Note: Only one definition for an entity with a given name with C language linkage may appear in
the program (see 3.2); this implies that such an entity must not be defined in more than one namespace
scope. — end note]

Your company’s or project’s global style arbiters should be able to advise you on a suitable naming policy for your code base.

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