https://github.com/spavloff created https://github.com/llvm/llvm-project/pull/131366
Const-qualification of an array caused by constexpr specifier can produce QualType, where the const qualifier is set both as fast qualifier and as a qualifier of the array element type. It can result in a compiler crash, because such QualType does not compare equal to the same type but without extra qualification. As a fix, the const qualifier is moved to the array element type when setting the implicit const. It fixes https://github.com/llvm/llvm-project/issues/97005 (Clang crashed in ASTContext::getCommonSugaredType). >From 22e4fa0d003679135000cdf0d0bb48fd1b3ee7fe Mon Sep 17 00:00:00 2001 From: Serge Pavlov <sepavl...@gmail.com> Date: Thu, 13 Mar 2025 12:35:59 +0700 Subject: [PATCH] Move const qualification of array to its elements Const-qualification of an array caused by constexpr specifier can produce QualType, where the const qualifier is set both as fast qualifier and as a qualifier of the array element type. It can result in a compiler crash, because such QualType does not compare equal to the same type but without extra qualification. As a fix, the const qualifier is moved to the array element type when setting the implicit const. It fixes https://github.com/llvm/llvm-project/issues/97005 (Clang crashed in ASTContext::getCommonSugaredType). --- clang/lib/Sema/SemaType.cpp | 7 ++++++- clang/test/AST/ByteCode/constexpr.c | 2 +- clang/test/Sema/constexpr.c | 2 +- clang/test/SemaCXX/constexpr-implicit-const-97005.cpp | 8 ++++++++ 4 files changed, 16 insertions(+), 3 deletions(-) create mode 100644 clang/test/SemaCXX/constexpr-implicit-const-97005.cpp diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp index 11943c0b53591..dee678aa69e83 100644 --- a/clang/lib/Sema/SemaType.cpp +++ b/clang/lib/Sema/SemaType.cpp @@ -5613,8 +5613,13 @@ static TypeSourceInfo *GetFullTypeForDeclarator(TypeProcessingState &state, // A constexpr specifier used in an object declaration declares the object // as const. if (D.getDeclSpec().getConstexprSpecifier() == ConstexprSpecKind::Constexpr && - T->isObjectType()) + T->isObjectType()) { T.addConst(); + // C++ 9.3.3.4p3: Any type of the form "cv-qualifier-seq array of N U" is + // adjusted to "array of N cv-qualifier-seq U". + if (const ArrayType *AType = Context.getAsArrayType(T)) + T = QualType(AType, 0); + } // C++2a [dcl.fct]p4: // A parameter with volatile-qualified type is deprecated diff --git a/clang/test/AST/ByteCode/constexpr.c b/clang/test/AST/ByteCode/constexpr.c index af96bf3a06f37..a4a8bde266e76 100644 --- a/clang/test/AST/ByteCode/constexpr.c +++ b/clang/test/AST/ByteCode/constexpr.c @@ -82,7 +82,7 @@ constexpr TheA V19[3] = {}; constexpr TheV V20[3] = {}; // both-error@-1 {{constexpr variable cannot have type 'const TheV[3]' (aka 'const volatile short[3]')}} constexpr TheR V21[3] = {}; -// both-error@-1 {{constexpr variable cannot have type 'const TheR[3]' (aka 'float *restrict const[3]')}} +// both-error@-1 {{constexpr variable cannot have type 'const TheR[3]' (aka 'float *const restrict[3]')}} struct HasA { TheA f; diff --git a/clang/test/Sema/constexpr.c b/clang/test/Sema/constexpr.c index 3dcb0b3a7d95f..005e980563cc7 100644 --- a/clang/test/Sema/constexpr.c +++ b/clang/test/Sema/constexpr.c @@ -81,7 +81,7 @@ constexpr TheA V19[3] = {}; constexpr TheV V20[3] = {}; // expected-error@-1 {{constexpr variable cannot have type 'const TheV[3]' (aka 'const volatile short[3]')}} constexpr TheR V21[3] = {}; -// expected-error@-1 {{constexpr variable cannot have type 'const TheR[3]' (aka 'float *restrict const[3]')}} +// expected-error@-1 {{constexpr variable cannot have type 'const TheR[3]' (aka 'float *const restrict[3]')}} struct HasA { TheA f; diff --git a/clang/test/SemaCXX/constexpr-implicit-const-97005.cpp b/clang/test/SemaCXX/constexpr-implicit-const-97005.cpp new file mode 100644 index 0000000000000..78e9b11f4d61c --- /dev/null +++ b/clang/test/SemaCXX/constexpr-implicit-const-97005.cpp @@ -0,0 +1,8 @@ +// RUN: %clang_cc1 -triple x86_64-linux-gnu -ast-dump %s | FileCheck %s + +bool aaa; +constexpr const unsigned char ccc[] = { 5 }; +constexpr const unsigned char ddd[1] = { 0 }; +auto bbb = (aaa ? ddd : ccc); + +// CHECK: DeclRefExpr {{.*}} 'const unsigned char[1]' {{.*}} 'ddd' 'const unsigned char[1]' _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
