aaron.ballman created this revision.
aaron.ballman added reviewers: erichkeane, rjmccall, efriedma,
clang-language-wg.
Herald added a project: All.
aaron.ballman requested review of this revision.
Herald added a project: clang.
Clang currently crashes when lowering a consteval list initialization of a
temporary. This is partially working around an issue in the template
instantiation code (`TreeTransform::TransformCXXTemporaryObjectExpr()`) that
does not yet know how to handle list initialization of temporaries in all
cases. However, it's also helping reduce fragility by ensuring we always have a
valid `QualType` when trying to emit a constant expression during IR generation.
Fixes #55871
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D131194
Files:
clang/docs/ReleaseNotes.rst
clang/lib/CodeGen/CGExprConstant.cpp
clang/test/CodeGenCXX/cxx20-consteval-crash.cpp
Index: clang/test/CodeGenCXX/cxx20-consteval-crash.cpp
===================================================================
--- clang/test/CodeGenCXX/cxx20-consteval-crash.cpp
+++ clang/test/CodeGenCXX/cxx20-consteval-crash.cpp
@@ -56,3 +56,18 @@
// CHECK: define{{.*}} signext i8 @_ZN10Issue545782f2IcEEcT_(
// CHECK: ret i8 4
}
+
+namespace Issue55871 {
+struct Item {
+ consteval Item(char c) :_char{c}{}
+ char _char;
+};
+
+int function(const Item& item1, const Item& item2) {
+ return 0;
+}
+
+int foo() {
+ return function(Item{'a'}, Item{'a'});
+}
+} // namespace Issue58871
Index: clang/lib/CodeGen/CGExprConstant.cpp
===================================================================
--- clang/lib/CodeGen/CGExprConstant.cpp
+++ clang/lib/CodeGen/CGExprConstant.cpp
@@ -1396,11 +1396,24 @@
if (!CE->hasAPValueResult())
return nullptr;
const Expr *Inner = CE->getSubExpr()->IgnoreImplicit();
- QualType RetType;
+
+ // In a call below, emitAbstract() calls tryEmitPrivate() and *some parts* of
+ // that call will use the RetType we pass in here. The parts which do make
+ // use of it expect that the QualType is valid, which is why we give it a
+ // default value here and reset the type only as needed.
+ QualType RetType = Inner->getType();
if (auto *Call = dyn_cast<CallExpr>(Inner))
RetType = Call->getCallReturnType(CGM.getContext());
else if (auto *Ctor = dyn_cast<CXXConstructExpr>(Inner))
RetType = Ctor->getType();
+ else if (auto *Cast = dyn_cast<CXXFunctionalCastExpr>(Inner)) {
+ // FIXME: This is working around a deficiency in template instantiation;
+ // see TreeTransform::TransformCXXTemporaryObjectExpr and GitHub Issue
+ // #55871 for more details.
+ RetType = Cast->getType();
+ }
+
+ assert(!RetType.isNull() && "Not certain of the constant expression's type");
llvm::Constant *Res =
emitAbstract(CE->getBeginLoc(), CE->getAPValueResult(), RetType);
return Res;
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -60,6 +60,9 @@
- No longer assert/miscompile when trying to make a vectorized ``_BitInt`` type
using the ``ext_vector_type`` attribute (the ``vector_size`` attribute was
already properly diagnosing this case).
+- Fixed a crash-on-valid with consteval evaluation of a list-initialized
+ constructor for a temporary object. This fixes
+ `Issue 55871 <https://github.com/llvm/llvm-project/issues/55871>`_.
Improvements to Clang's diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
Index: clang/test/CodeGenCXX/cxx20-consteval-crash.cpp
===================================================================
--- clang/test/CodeGenCXX/cxx20-consteval-crash.cpp
+++ clang/test/CodeGenCXX/cxx20-consteval-crash.cpp
@@ -56,3 +56,18 @@
// CHECK: define{{.*}} signext i8 @_ZN10Issue545782f2IcEEcT_(
// CHECK: ret i8 4
}
+
+namespace Issue55871 {
+struct Item {
+ consteval Item(char c) :_char{c}{}
+ char _char;
+};
+
+int function(const Item& item1, const Item& item2) {
+ return 0;
+}
+
+int foo() {
+ return function(Item{'a'}, Item{'a'});
+}
+} // namespace Issue58871
Index: clang/lib/CodeGen/CGExprConstant.cpp
===================================================================
--- clang/lib/CodeGen/CGExprConstant.cpp
+++ clang/lib/CodeGen/CGExprConstant.cpp
@@ -1396,11 +1396,24 @@
if (!CE->hasAPValueResult())
return nullptr;
const Expr *Inner = CE->getSubExpr()->IgnoreImplicit();
- QualType RetType;
+
+ // In a call below, emitAbstract() calls tryEmitPrivate() and *some parts* of
+ // that call will use the RetType we pass in here. The parts which do make
+ // use of it expect that the QualType is valid, which is why we give it a
+ // default value here and reset the type only as needed.
+ QualType RetType = Inner->getType();
if (auto *Call = dyn_cast<CallExpr>(Inner))
RetType = Call->getCallReturnType(CGM.getContext());
else if (auto *Ctor = dyn_cast<CXXConstructExpr>(Inner))
RetType = Ctor->getType();
+ else if (auto *Cast = dyn_cast<CXXFunctionalCastExpr>(Inner)) {
+ // FIXME: This is working around a deficiency in template instantiation;
+ // see TreeTransform::TransformCXXTemporaryObjectExpr and GitHub Issue
+ // #55871 for more details.
+ RetType = Cast->getType();
+ }
+
+ assert(!RetType.isNull() && "Not certain of the constant expression's type");
llvm::Constant *Res =
emitAbstract(CE->getBeginLoc(), CE->getAPValueResult(), RetType);
return Res;
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -60,6 +60,9 @@
- No longer assert/miscompile when trying to make a vectorized ``_BitInt`` type
using the ``ext_vector_type`` attribute (the ``vector_size`` attribute was
already properly diagnosing this case).
+- Fixed a crash-on-valid with consteval evaluation of a list-initialized
+ constructor for a temporary object. This fixes
+ `Issue 55871 <https://github.com/llvm/llvm-project/issues/55871>`_.
Improvements to Clang's diagnostics
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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