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This patch is an attempt to implement (part of?) P2280, Using unknown pointers and references in constant expressions. (Note that R4 seems to only allow References to unknown/Accesses via this, but not Pointers to unknown.) This patch works to the extent that the test case added in [expr.const] works as expected, as well as the test in <https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2022/p2280r4.html#the-this-pointer> Most importantly, the proposal makes this compile: template <typename T, size_t N> constexpr auto array_size(T (&)[N]) -> size_t { return N; } void check(int const (¶m)[3]) { constexpr auto s = array_size(param); static_assert (s == 3); } and I think it would be a pity not to have it in GCC 14. What still doesn't work is the test in $3.2: struct A2 { constexpr int f() { return 0; } }; struct B2 : virtual A2 {}; void f2(B2 &b) { constexpr int k = b.f(); } where we say error: '* & b' is not a constant expression This will be fixed in the future. PR c++/106650 gcc/cp/ChangeLog: * constexpr.cc (cxx_eval_constant_expression) <case PARM_DECL>: Allow reference to unknown/this as per P2280. <case VAR_DECL>: Allow reference to unknown as per P2280. gcc/testsuite/ChangeLog: * g++.dg/cpp0x/constexpr-array-ptr6.C: Remove dg-error. * g++.dg/cpp0x/constexpr-ref12.C: Likewise. * g++.dg/cpp0x/constexpr-ref2.C: Adjust dg-error. * g++.dg/cpp0x/noexcept34.C: Remove dg-error. * g++.dg/cpp1y/lambda-generic-const10.C: Likewise. * g++.dg/cpp0x/constexpr-ref13.C: New test. * g++.dg/cpp1z/constexpr-ref1.C: New test. * g++.dg/cpp1z/constexpr-ref2.C: New test. * g++.dg/cpp2a/constexpr-ref1.C: New test.
25 lines
470 B
C
25 lines
470 B
C
// PR c++/82643
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// { dg-do compile { target c++14 } }
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int main()
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{
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struct A {
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constexpr int operator()() const { return 42; }
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};
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auto f = A();
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constexpr auto x = f(); //ok, call constexpr const non-static method
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[](auto const &f) {
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constexpr auto x = f();
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}(f);
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[&]() {
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constexpr auto x = f(); //ko, __closure is not a constant expression
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};
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[=]() {
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constexpr auto x = f(); //same ko, __closure is not a constant expression
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};
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}
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