[cfe-dev] Clang disagrees with gcc at the intersection of explicit template instantiations and visibility

[Keno Fischer via cfe-dev]

Hi folks,

I've been looking at explicit template instantiations lately, and came
across the following
corner case where gcc and clang disagree on the visibility of a symbol. I'm
inclined to think gcc's behavior is correct, but I wanted to make sure I'm
not missing some reason why AddS needs to be visible.

Consider the following file (test.cpp):

template < typename T > class foo {
public:
    T x;
    T getX() { return x; }
    template < typename S >
    __attribute__ ((visibility("hidden"))) S AddS(S);
};

__attribute__ ((visibility("hidden"))) S foo<T>::AddS(S y) {
    return ((S) x) + y;
}

template < typename T, typename S >
__attribute__ ((visibility("hidden"))) S AddTS(T x, S y) {
    return ((S) x) + y;
}

extern template struct foo<int>;
template struct foo<int>;

int footest() {
    auto var = foo<int>{5};
    auto bar = var.AddS((long long)3);
    auto bar2 = AddTS((int)5,(long long)3);
    return var.getX();
}


$ gcc -std=c++11 -c -S -o - test.cpp | grep .hidden
.hidden _ZN3fooIiE4AddSIxEET_S2_
.hidden _Z5AddTSIixET0_T_S0_
$ clang-3.5 -std=c++11 -c -S -o - test.cpp | grep .hidden
.hidden _Z5AddTSIixET0_T_S0_
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