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b3e6ff3319
This commit introduces support for the MSVC-specific C++11-style attribute `[[msvc::constexpr]]`, which was introduced in MSVC 14.33. The semantics of this attribute are enabled only under MSVC compatibility (`-fms-compatibility-version`) 14.33 and higher. Additionally, the default value of `_MSC_VER` has been raised to 1433. The current implementation lacks support for: - `[[msvc::constexpr]]` constructors (see #72149); at the time of this implementation, such support would have required an unreasonable number of changes in Clang. - `[[msvc::constexpr]] return ::new` (constexpr placement new) from non-std namespaces (see #74924). Relevant to: #57696
38 lines
1.8 KiB
C++
38 lines
1.8 KiB
C++
// RUN: %clang_cc1 -fms-compatibility -fms-compatibility-version=19.33 -std=c++20 -verify %s
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[[msvc::constexpr]] int log2(int x) { [[msvc::constexpr]] return x > 1 ? 1 + log2(x / 2) : 0; }
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constexpr bool test_log2() { [[msvc::constexpr]] return log2(32) == 5; }
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static_assert(test_log2());
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[[msvc::constexpr]] int get_value(int x)
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{
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switch (x)
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{
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case 42: return 1337;
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default:
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if (x < 0) [[msvc::constexpr]] return log2(-x);
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else return x;
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}
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}
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constexpr bool test_complex_expr() {
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[[msvc::constexpr]] return get_value(get_value(42) - 1337 + get_value(-32) - 5 + (get_value(1) ? get_value(0) : get_value(2))) == get_value(0);
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}
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static_assert(test_complex_expr());
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constexpr bool get_constexpr_true() { return true; }
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[[msvc::constexpr]] bool get_msconstexpr_true() { return get_constexpr_true(); }
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constexpr bool test_get_msconstexpr_true() { [[msvc::constexpr]] return get_msconstexpr_true(); }
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static_assert(test_get_msconstexpr_true());
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// TODO (#72149): Add support for [[msvc::constexpr]] constructor; this code is valid for MSVC.
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struct S2 {
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[[msvc::constexpr]] S2() {}
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[[msvc::constexpr]] bool value() { return true; }
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static constexpr bool check() { [[msvc::constexpr]] return S2{}.value(); } // expected-error {{constexpr function never produces a constant expression}} \
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// expected-note {{non-literal type 'S2' cannot be used in a constant expression}} \
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// expected-note {{non-literal type 'S2' cannot be used in a constant expression}}
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};
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static_assert(S2::check()); // expected-error {{static assertion expression is not an integral constant expression}} \
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// expected-note {{in call to 'check()'}}
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