Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk? -- >8 -- Consider
constexpr int VAL = 1; struct foo { template <int B> void bar(typename std::conditional<B==VAL, int, float>::type arg) { } }; template void foo::bar<1>(int arg); where we since r11-291 fail to emit the code for the explicit instantiation. That's because cp_walk_subtrees/TYPENAME_TYPE now walks TYPE_CONTEXT ('conditional' here) as well, and in a template finds the B==VAL template argument. VAL is constexpr, which implies const, which in the global scope implies static. constrain_visibility_for_template then makes "struct conditional<(B == VAL), int, float>" non-TREE_PUBLIC. Then symtab_node::needed_p checks TREE_PUBLIC, sees it's 0, and we don't emit any code. I thought the fix would be some ODR-esque check to not consider constexpr variables/fns that are used just for their value. But it turned out to be tricky. For instance, we can't skip determine_visibility in a template; we can't even skip it for value-dep expressions. For example, no-linkage-expr1.C has using P = struct {}*; template <int N> void f(int(*)[((P)0, N)]) {} where ((P)0, N) is value-dep, but N is not relevant here: we have to ferret out the anonymous type. When instantiating, it's already gone. The best I could come up with is to disregard _DECL in min_vis_expr_r in a template while still checking type_visibility, even in a template. PR c++/110323 gcc/cp/ChangeLog: * decl2.cc (min_vis_expr_r) <case VAR_DECL>: Do nothing in a template. gcc/testsuite/ChangeLog: * g++.dg/template/explicit-instantiation6.C: New test. * g++.dg/template/explicit-instantiation7.C: New test. --- gcc/cp/decl2.cc | 6 ++- .../g++.dg/template/explicit-instantiation6.C | 53 +++++++++++++++++++ .../g++.dg/template/explicit-instantiation7.C | 22 ++++++++ 3 files changed, 80 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/g++.dg/template/explicit-instantiation6.C create mode 100644 gcc/testsuite/g++.dg/template/explicit-instantiation7.C diff --git a/gcc/cp/decl2.cc b/gcc/cp/decl2.cc index 6c9fd415d40..3e035a7bf9f 100644 --- a/gcc/cp/decl2.cc +++ b/gcc/cp/decl2.cc @@ -2718,7 +2718,11 @@ min_vis_expr_r (tree *tp, int */*walk_subtrees*/, void *data) /* Fall through. */ case VAR_DECL: case FUNCTION_DECL: - if (! TREE_PUBLIC (t)) + if (processing_template_decl) + /* In a template, we can't trust _DECLs, either. It's possible + they won't be ODR-used, and we could wrongly think the linkage + is internal (PR110323). */; + else if (! TREE_PUBLIC (t)) tpvis = VISIBILITY_ANON; else tpvis = DECL_VISIBILITY (t); diff --git a/gcc/testsuite/g++.dg/template/explicit-instantiation6.C b/gcc/testsuite/g++.dg/template/explicit-instantiation6.C new file mode 100644 index 00000000000..399c7d72756 --- /dev/null +++ b/gcc/testsuite/g++.dg/template/explicit-instantiation6.C @@ -0,0 +1,53 @@ +// PR c++/110323 +// { dg-do compile { target c++14 } } + +template<bool B, class T, class F> +struct conditional { using type = T; }; + +template<class T, class F> +struct conditional<false, T, F> { using type = F; }; + +constexpr int VAL = 1; + +static constexpr int getval () { return 1; } + +template<typename> +constexpr int TVAL = 1; + +static struct S { + constexpr operator bool() { return true; } +} s; + +struct foo { + template <int B> + void bar(typename conditional<B == VAL, int, float>::type arg) { } + + template <int B> + void baz(typename conditional<B == getval (), int, float>::type arg) { } + + template <int B> + void qux(typename conditional<B == TVAL<int>, int, float>::type arg) { } + + template <int B> + void lox(typename conditional<B == s, int, float>::type arg) { } + + template <int B> + void sox(typename conditional<B == noexcept (VAL), int, float>::type arg) { } + + template <int B> + void nim(typename conditional<B != sizeof (VAL), int, float>::type arg) { } +}; + +template void foo::bar<1>(int arg); +template void foo::baz<1>(int arg); +template void foo::qux<1>(int arg); +template void foo::lox<1>(int arg); +template void foo::sox<1>(int arg); +template void foo::nim<1>(int arg); + +// { dg-final { scan-assembler "_ZN3foo3barILi1EEEvN11conditionalIXeqT_L_ZL3VALEEifE4typeE" } } +// { dg-final { scan-assembler "_ZN3foo3bazILi1EEEvN11conditionalIXeqT_clL_ZL6getvalvEEEifE4typeE" } } +// { dg-final { scan-assembler "_ZN3foo3quxILi1EEEvN11conditionalIXeqT_L_Z4TVALIiEEEifE4typeE" } } +// { dg-final { scan-assembler "_ZN3foo3loxILi1EEEvN11conditionalIXeqT_L_ZL1sEEifE4typeE" } } +// { dg-final { scan-assembler "_ZN3foo3soxILi1EEEvN11conditionalIXeqT_nxL_ZL3VALEEifE4typeE" } } +// { dg-final { scan-assembler "_ZN3foo3nimILi1EEEvN11conditionalIXneT_szL_ZL3VALEEifE4typeE" } } diff --git a/gcc/testsuite/g++.dg/template/explicit-instantiation7.C b/gcc/testsuite/g++.dg/template/explicit-instantiation7.C new file mode 100644 index 00000000000..9a870e808fa --- /dev/null +++ b/gcc/testsuite/g++.dg/template/explicit-instantiation7.C @@ -0,0 +1,22 @@ +// PR c++/110323 +// { dg-do compile { target c++11 } } + +using P = struct { }*; +using N = struct A { }*; + +template<bool B, class T, class F> +struct conditional { using type = T; }; + +struct foo { + template <int B> + void bar(typename conditional<((P) 0, B), int, float>::type arg) { } + + template <int B> + void baz(typename conditional<((N) 0, B), int, float>::type arg) { } +}; + +template void foo::bar<1>(int arg); +template void foo::baz<1>(int arg); + +// { dg-final { scan-assembler-not "_ZN3foo3barILi1EEEvN11conditionalIXcmcvP1XLi0EneT_Li0EEifE4typeE" } } +// { dg-final { scan-assembler "_ZN3foo3bazILi1EEEvN11conditionalIXcmcvP1ALi0EneT_Li0EEifE4typeE" } } base-commit: 10c609191c4462133d6a4ea10a739167204f2cd3 -- 2.44.0