[clang] f27afed - [Clang] Implement P2738R1 - constexpr cast from void*
Corentin Jabot via cfe-commits
cfe-commits at lists.llvm.org
Mon Jun 26 07:45:13 PDT 2023
Author: Corentin Jabot
Date: 2023-06-26T16:45:07+02:00
New Revision: f27afedc6c86fd9c9dd576379f4d60d892a2ce67
URL: https://github.com/llvm/llvm-project/commit/f27afedc6c86fd9c9dd576379f4d60d892a2ce67
DIFF: https://github.com/llvm/llvm-project/commit/f27afedc6c86fd9c9dd576379f4d60d892a2ce67.diff
LOG: [Clang] Implement P2738R1 - constexpr cast from void*
Reviewed By: #clang-language-wg, erichkeane
Differential Revision: https://reviews.llvm.org/D153702
Added:
clang/test/CXX/expr/expr.const/p5-26.cpp
Modified:
clang/docs/ReleaseNotes.rst
clang/include/clang/Basic/DiagnosticASTKinds.td
clang/lib/AST/ExprConstant.cpp
clang/lib/Frontend/InitPreprocessor.cpp
clang/test/Lexer/cxx-features.cpp
clang/www/cxx_status.html
Removed:
################################################################################
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index 76f5313cd8fa5..055aa9008b03b 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -132,6 +132,7 @@ C++23 Feature Support
C++2c Feature Support
^^^^^^^^^^^^^^^^^^^^^
- Compiler flags ``-std=c++2c`` and ``-std=gnu++2c`` have been added for experimental C++2c implementation work.
+- Implemented `P2738R1: constexpr cast from void* <https://wg21.link/P2738R1>`_.
Resolutions to C++ Defect Reports
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
diff --git a/clang/include/clang/Basic/DiagnosticASTKinds.td b/clang/include/clang/Basic/DiagnosticASTKinds.td
index 73118891c1899..856293dd45d08 100644
--- a/clang/include/clang/Basic/DiagnosticASTKinds.td
+++ b/clang/include/clang/Basic/DiagnosticASTKinds.td
@@ -15,6 +15,10 @@ def note_constexpr_invalid_cast : Note<
" performs the conversions of a reinterpret_cast}1|cast from %1}0"
" is not allowed in a constant expression"
"%select{| in C++ standards before C++20||}0">;
+def note_constexpr_invalid_void_star_cast : Note<
+ "cast from %0 is not allowed in a constant expression "
+ "%select{in C++ standards before C++2c|because the pointed object "
+ "type %2 is not similar to the target type %3}1">;
def note_constexpr_invalid_downcast : Note<
"cannot cast object of dynamic type %0 to type %1">;
def note_constexpr_overflow : Note<
diff --git a/clang/lib/AST/ExprConstant.cpp b/clang/lib/AST/ExprConstant.cpp
index 65d69d9b49438..19d8e24fef63c 100644
--- a/clang/lib/AST/ExprConstant.cpp
+++ b/clang/lib/AST/ExprConstant.cpp
@@ -8897,9 +8897,10 @@ bool PointerExprEvaluator::VisitCastExpr(const CastExpr *E) {
if (!E->getType()->isVoidPointerType()) {
// In some circumstances, we permit casting from void* to cv1 T*, when the
// actual pointee object is actually a cv2 T.
+ bool HasValidResult = !Result.InvalidBase && !Result.Designator.Invalid &&
+ !Result.IsNullPtr;
bool VoidPtrCastMaybeOK =
- !Result.InvalidBase && !Result.Designator.Invalid &&
- !Result.IsNullPtr &&
+ HasValidResult &&
Info.Ctx.hasSameUnqualifiedType(Result.Designator.getType(Info.Ctx),
E->getType()->getPointeeType());
// 1. We'll allow it in std::allocator::allocate, and anything which that
@@ -8911,16 +8912,23 @@ bool PointerExprEvaluator::VisitCastExpr(const CastExpr *E) {
// that back to `const __impl*` in its body.
if (VoidPtrCastMaybeOK &&
(Info.getStdAllocatorCaller("allocate") ||
- IsDeclSourceLocationCurrent(Info.CurrentCall->Callee))) {
+ IsDeclSourceLocationCurrent(Info.CurrentCall->Callee) ||
+ Info.getLangOpts().CPlusPlus26)) {
// Permitted.
} else {
- Result.Designator.setInvalid();
- if (SubExpr->getType()->isVoidPointerType())
- CCEDiag(E, diag::note_constexpr_invalid_cast)
- << 3 << SubExpr->getType();
- else
+ if (SubExpr->getType()->isVoidPointerType()) {
+ if (HasValidResult)
+ CCEDiag(E, diag::note_constexpr_invalid_void_star_cast)
+ << SubExpr->getType() << Info.getLangOpts().CPlusPlus26
+ << Result.Designator.getType(Info.Ctx).getCanonicalType()
+ << E->getType()->getPointeeType();
+ else
+ CCEDiag(E, diag::note_constexpr_invalid_cast)
+ << 3 << SubExpr->getType();
+ } else
CCEDiag(E, diag::note_constexpr_invalid_cast)
<< 2 << Info.Ctx.getLangOpts().CPlusPlus;
+ Result.Designator.setInvalid();
}
}
if (E->getCastKind() == CK_AddressSpaceConversion && Result.IsNullPtr)
diff --git a/clang/lib/Frontend/InitPreprocessor.cpp b/clang/lib/Frontend/InitPreprocessor.cpp
index 76392c104de26..431b9ea36c434 100644
--- a/clang/lib/Frontend/InitPreprocessor.cpp
+++ b/clang/lib/Frontend/InitPreprocessor.cpp
@@ -611,7 +611,8 @@ static void InitializeCPlusPlusFeatureTestMacros(const LangOptions &LangOpts,
Builder.defineMacro("__cpp_unicode_literals", "200710L");
Builder.defineMacro("__cpp_user_defined_literals", "200809L");
Builder.defineMacro("__cpp_lambdas", "200907L");
- Builder.defineMacro("__cpp_constexpr", LangOpts.CPlusPlus23 ? "202211L"
+ Builder.defineMacro("__cpp_constexpr", LangOpts.CPlusPlus26 ? "202306L"
+ : LangOpts.CPlusPlus23 ? "202211L"
: LangOpts.CPlusPlus20 ? "201907L"
: LangOpts.CPlusPlus17 ? "201603L"
: LangOpts.CPlusPlus14 ? "201304L"
diff --git a/clang/test/CXX/expr/expr.const/p5-26.cpp b/clang/test/CXX/expr/expr.const/p5-26.cpp
new file mode 100644
index 0000000000000..03d28d39fd3bb
--- /dev/null
+++ b/clang/test/CXX/expr/expr.const/p5-26.cpp
@@ -0,0 +1,39 @@
+// RUN: %clang_cc1 -fsyntax-only -std=c++2c -verify=expected,cxx26 %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++2b -verify=expected=cxx23 %s
+
+
+struct S {};
+struct T : S {} t;
+
+consteval void test() { // cxx23-error{{consteval function never produces a constant expression}}
+ void* a = &t;
+ const void* b = &t;
+ volatile void* c = &t;
+ (void)static_cast<T*>(a); //cxx23-note {{cast from 'void *' is not allowed in a constant expression in C++ standards before C++2c}}
+ (void)static_cast<const T*>(a);
+ (void)static_cast<volatile T*>(a);
+
+ (void)(T*)(a);
+ (void)(const T*)(a);
+ (void)(volatile T*)(a);
+
+ (void)static_cast<T*>(b); // expected-error {{static_cast from 'const void *' to 'T *' casts away qualifiers}}
+ (void)static_cast<volatile T*>(b); // expected-error {{static_cast from 'const void *' to 'volatile T *' casts away qualifiers}}
+ (void)static_cast<const T*>(b);
+ (void)static_cast<volatile const T*>(b);
+
+ (void)static_cast<T*>(c); // expected-error{{static_cast from 'volatile void *' to 'T *' casts away qualifiers}}
+ (void)static_cast<volatile T*>(c);
+ (void)static_cast<const T*>(b);
+ (void)static_cast<volatile const T*>(b);
+}
+
+void err() {
+ constexpr void* a = &t;
+ constexpr auto err1 = static_cast<int*>(a); // expected-error{{constexpr variable 'err1' must be initialized by a constant expression}} \
+ // cxx23-note {{cast from 'void *' is not allowed in a constant expression in C++ standards before C++2c}} \
+ // cxx26-note {{cast from 'void *' is not allowed in a constant expression because the pointed object type 'T' is not similar to the target type 'int'}}
+ constexpr auto err2 = static_cast<S*>(a); // expected-error{{constexpr variable 'err2' must be initialized by a constant expression}} \
+ // cxx23-note {{cast from 'void *' is not allowed in a constant expression in C++ standards before C++2c}} \
+ // cxx26-note {{cast from 'void *' is not allowed in a constant expression because the pointed object type 'T' is not similar to the target type 'S'}}
+}
diff --git a/clang/test/Lexer/cxx-features.cpp b/clang/test/Lexer/cxx-features.cpp
index 1b6c793e1defb..5c5408c29f879 100644
--- a/clang/test/Lexer/cxx-features.cpp
+++ b/clang/test/Lexer/cxx-features.cpp
@@ -300,7 +300,7 @@
#error "wrong value for __cpp_lambdas"
#endif
-#if check(constexpr, 0, 200704, 201304, 201603, 201907, 202211, 202211)
+#if check(constexpr, 0, 200704, 201304, 201603, 201907, 202211, 202306)
#error "wrong value for __cpp_constexpr"
#endif
diff --git a/clang/www/cxx_status.html b/clang/www/cxx_status.html
index 4eea21cb9da47..94c96ba0614e2 100755
--- a/clang/www/cxx_status.html
+++ b/clang/www/cxx_status.html
@@ -125,7 +125,7 @@ <h2 id="cxx26">C++2c implementation status</h2>
<tr>
<td>constexpr cast from <tt>void*</tt></td>
<td><a href="https://wg21.link/P2738R1">P2738R1</a></td>
- <td class="none" align="center">No</td>
+ <td class="unreleased" align="center">Clang 17</td>
</tr>
<tr>
<td>On the ignorability of standard attributes</td>
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