[clang] 00e2098 - [Clang] Implement CWG2518 - static_assert(false)
Corentin Jabot via cfe-commits
cfe-commits at lists.llvm.org
Tue Feb 28 08:21:47 PST 2023
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>
More information about the cfe-commits
mailing list