Author: Corentin Jabot Date: 2023-02-28T17:21:40+01:00 New Revision: 00e2098bf49f0ed45b3b8c22894cd3ac9a530e0f
URL: https://github.com/llvm/llvm-project/commit/00e2098bf49f0ed45b3b8c22894cd3ac9a530e0f DIFF: https://github.com/llvm/llvm-project/commit/00e2098bf49f0ed45b3b8c22894cd3ac9a530e0f.diff LOG: [Clang] Implement CWG2518 - static_assert(false) This allows `static_assert(false)` to not be ill-formed in template definitions. This change is applied as a DR in all C++ modes. Of notes, a couple of tests were relying of the eager nature of static_assert * test/SemaTemplate/instantiation-dependence.cpp * test/SemaTemplate/instantiate-var-template.cpp I don't know if the changes to `static_assert` still allow that sort of tests to be expressed. Reviewed By: #clang-language-wg, erichkeane, aaron.ballman Differential Revision: https://reviews.llvm.org/D144285 Added: Modified: clang/docs/ReleaseNotes.rst clang/lib/Sema/SemaDeclCXX.cpp clang/test/CXX/drs/dr25xx.cpp clang/test/SemaCXX/access-base-class.cpp clang/test/SemaCXX/coroutines.cpp clang/test/SemaCXX/static-assert.cpp clang/test/SemaTemplate/instantiate-var-template.cpp clang/test/SemaTemplate/instantiation-dependence.cpp clang/www/cxx_dr_status.html Removed: ################################################################################ diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst index 1cc9e4efac1fe..d24dab5edad00 100644 --- a/clang/docs/ReleaseNotes.rst +++ b/clang/docs/ReleaseNotes.rst @@ -73,6 +73,8 @@ C++ Language Changes - Improved ``-O0`` code generation for calls to ``std::forward_like``. Similarly to ``std::move, std::forward`` et al. it is now treated as a compiler builtin and implemented directly rather than instantiating the definition from the standard library. +- Implemented `CWG2518 <https://wg21.link/CWG2518>`_ which allows ``static_assert(false)`` + to not be ill-formed when its condition is evaluated in the context of a template definition. C++20 Feature Support ^^^^^^^^^^^^^^^^^^^^^ diff --git a/clang/lib/Sema/SemaDeclCXX.cpp b/clang/lib/Sema/SemaDeclCXX.cpp index 6ec0eacf7a37c..ec85d503ccf8f 100644 --- a/clang/lib/Sema/SemaDeclCXX.cpp +++ b/clang/lib/Sema/SemaDeclCXX.cpp @@ -16784,7 +16784,14 @@ Decl *Sema::BuildStaticAssertDeclaration(SourceLocation StaticAssertLoc, FoldKind).isInvalid()) Failed = true; - if (!Failed && !Cond) { + // CWG2518 + // [dcl.pre]/p10 If [...] the expression is evaluated in the context of a + // template definition, the declaration has no effect. + bool InTemplateDefinition = + getLangOpts().CPlusPlus && CurContext->isDependentContext(); + + if (!Failed && !Cond && !InTemplateDefinition) { + SmallString<256> MsgBuffer; llvm::raw_svector_ostream Msg(MsgBuffer); if (AssertMessage) { @@ -16815,7 +16822,8 @@ Decl *Sema::BuildStaticAssertDeclaration(SourceLocation StaticAssertLoc, DiagnoseStaticAssertDetails(InnerCond); } else { Diag(StaticAssertLoc, diag::err_static_assert_failed) - << !AssertMessage << Msg.str() << AssertExpr->getSourceRange(); + << !AssertMessage << Msg.str() << AssertExpr->getSourceRange(); + PrintContextStack(); } Failed = true; } diff --git a/clang/test/CXX/drs/dr25xx.cpp b/clang/test/CXX/drs/dr25xx.cpp index ee68b4ad45d11..c4f7d3ebde413 100644 --- a/clang/test/CXX/drs/dr25xx.cpp +++ b/clang/test/CXX/drs/dr25xx.cpp @@ -1,5 +1,39 @@ // RUN: %clang_cc1 -std=c++20 -triple x86_64-unknown-unknown %s -verify +namespace dr2518 { // dr2518: 17 review + +template <class T> +void f(T t) { + if constexpr (sizeof(T) != sizeof(int)) { + static_assert(false, "must be int-sized"); // expected-error {{must be int-size}} + } +} + +void g(char c) { + f(0); + f(c); // expected-note {{requested here}} +} + +template <typename Ty> +struct S { + static_assert(false); // expected-error {{static assertion failed}} +}; + +template <> +struct S<int> {}; + +template <> +struct S<float> {}; + +int test_specialization() { + S<int> s1; + S<float> s2; + S<double> s3; // expected-note {{in instantiation of template class 'dr2518::S<double>' requested here}} +} + +} + + namespace dr2565 { // dr2565: 16 open template<typename T> concept C = requires (typename T::type x) { diff --git a/clang/test/SemaCXX/access-base-class.cpp b/clang/test/SemaCXX/access-base-class.cpp index 2b16d3fdda568..47d0f02ec545c 100644 --- a/clang/test/SemaCXX/access-base-class.cpp +++ b/clang/test/SemaCXX/access-base-class.cpp @@ -96,14 +96,14 @@ struct flag { }; template <class T> -struct trait : flag<sizeof(T)> {}; +struct trait : flag<sizeof(T)> {}; // expected-note 2{{here}} -template <class T, bool Inferred = trait<T>::value> +template <class T, bool Inferred = trait<T>::value> // expected-note {{here}} struct a {}; template <class T> class b { - a<T> x; + a<T> x; // expected-note {{here}} using U = a<T>; }; @@ -113,5 +113,5 @@ struct Impossible { }; // verify "no member named 'value'" bogus diagnostic is not emitted. -trait<b<Impossible<0>>>::value; +trait<b<Impossible<0>>>::value; // expected-note {{here}} } // namespace T8 diff --git a/clang/test/SemaCXX/coroutines.cpp b/clang/test/SemaCXX/coroutines.cpp index 3f779dd913f8f..e480c0d34593a 100644 --- a/clang/test/SemaCXX/coroutines.cpp +++ b/clang/test/SemaCXX/coroutines.cpp @@ -1309,7 +1309,7 @@ struct DepTestType { } }; -template struct DepTestType<int>; // expected-note {{requested here}} +template struct DepTestType<int>; // expected-note 2{{requested here}} template CoroMemberTag DepTestType<int>::test_member_template(long, const char *) const &&; template CoroMemberTag DepTestType<int>::test_static_template<void>(const char *volatile &, unsigned); diff --git a/clang/test/SemaCXX/static-assert.cpp b/clang/test/SemaCXX/static-assert.cpp index ed2389f4eb100..97a3aaec0a08e 100644 --- a/clang/test/SemaCXX/static-assert.cpp +++ b/clang/test/SemaCXX/static-assert.cpp @@ -52,9 +52,11 @@ static_assert(false, "🏳️🌈 🏴 🇪🇺"); // template<typename T> struct AlwaysFails { // Only give one error here. - static_assert(false, ""); // expected-error {{static assertion failed}} + static_assert(false, ""); // expected-error 2{{static assertion failed}} }; -AlwaysFails<int> alwaysFails; +AlwaysFails<int> alwaysFails; // expected-note {{instantiation}} +AlwaysFails<double> alwaysFails2; // expected-note {{instantiation}} + template<typename T> struct StaticAssertProtected { static_assert(__is_literal(T), ""); // expected-error {{static assertion failed}} @@ -217,6 +219,23 @@ static_assert(constexprNotBool, "message"); // expected-error {{value of type 'c static_assert(1 , "") // expected-error {{expected ';' after 'static_assert'}} +namespace DependentAlwaysFalse { +template <typename Ty> +struct S { + static_assert(false); // expected-error{{static assertion failed}} \ + // expected-warning {{C++17 extension}} +}; + +template <typename Ty> +struct T { + static_assert(false, "test"); // expected-error{{static assertion failed: test}} +}; + +int f() { + S<double> s; //expected-note {{in instantiation of template class 'DependentAlwaysFalse::S<double>' requested here}} + T<double> t; //expected-note {{in instantiation of template class 'DependentAlwaysFalse::T<double>' requested here}} +} +} namespace Diagnostics { /// No notes for literals. diff --git a/clang/test/SemaTemplate/instantiate-var-template.cpp b/clang/test/SemaTemplate/instantiate-var-template.cpp index 349a80bdd0dc7..60d3bd3b59f53 100644 --- a/clang/test/SemaTemplate/instantiate-var-template.cpp +++ b/clang/test/SemaTemplate/instantiate-var-template.cpp @@ -31,8 +31,7 @@ namespace InstantiationDependent { static_assert(b<char> == 1, ""); // expected-note {{in instantiation of}} template<typename T> void f() { - static_assert(a<sizeof(sizeof(f(T())))> == 0, ""); // expected-error {{static assertion failed due to requirement 'a<sizeof (sizeof (f(type-parameter-0-0())))> == 0'}} \ - // expected-note {{evaluates to '1 == 0'}} + int check[a<sizeof(sizeof(f(T())))> == 0 ? 1 : -1]; // expected-error {{array with a negative size}} } } diff --git a/clang/test/SemaTemplate/instantiation-dependence.cpp b/clang/test/SemaTemplate/instantiation-dependence.cpp index 8ef18e8e0559a..82665b26b1229 100644 --- a/clang/test/SemaTemplate/instantiation-dependence.cpp +++ b/clang/test/SemaTemplate/instantiation-dependence.cpp @@ -37,8 +37,8 @@ namespace PR33655 { template<class ...Args> using indirect_void_t = typename indirect_void_t_imp<Args...>::type; template<class T> void foo() { - static_assert(!__is_void(indirect_void_t<T>)); // "ok", dependent - static_assert(!__is_void(void_t<T>)); // expected-error {{failed}} + int check1[__is_void(indirect_void_t<T>) == 0 ? 1 : -1]; // "ok", dependent + int check2[__is_void(void_t<T>) == 0 ? 1 : -1]; // expected-error {{array with a negative size}} } } diff --git a/clang/www/cxx_dr_status.html b/clang/www/cxx_dr_status.html index fdf8e6b4baeb1..f57aafcdb3090 100755 --- a/clang/www/cxx_dr_status.html +++ b/clang/www/cxx_dr_status.html @@ -14915,7 +14915,7 @@ <h2 id="cxxdr">C++ defect report implementation status</h2> <td><a href="https://wg21.link/cwg2518";>2518</a></td> <td>review</td> <td>Conformance requirements and <TT>#error</TT>/<TT>#warning</TT></td> - <td align="center">Not resolved</td> + <td class="unreleased" align="center">Clang 17</td> </tr> <tr class="open" id="2519"> <td><a href="https://wg21.link/cwg2519";>2519</a></td> _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
