r184024 - PR16263: Implement current direction of core issue 1376. Binding a reference to
Richard Smith
richard-llvm at metafoo.co.uk
Fri Jun 14 17:30:29 PDT 2013
Author: rsmith
Date: Fri Jun 14 19:30:29 2013
New Revision: 184024
URL: http://llvm.org/viewvc/llvm-project?rev=184024&view=rev
Log:
PR16263: Implement current direction of core issue 1376. Binding a reference to
the result of a cast-to-reference-type lifetime-extends the object to which the
reference inside the cast binds.
This requires us to look for subobject adjustments on both the inside and the
outside of the MaterializeTemporaryExpr when looking for a temporary to
lifetime-extend (which we also need for core issue 616, and possibly 1213).
Modified:
cfe/trunk/lib/AST/Expr.cpp
cfe/trunk/lib/Sema/SemaInit.cpp
cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp
cfe/trunk/test/CodeGenCXX/temporaries.cpp
Modified: cfe/trunk/lib/AST/Expr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=184024&r1=184023&r2=184024&view=diff
==============================================================================
--- cfe/trunk/lib/AST/Expr.cpp (original)
+++ cfe/trunk/lib/AST/Expr.cpp Fri Jun 14 19:30:29 2013
@@ -73,10 +73,10 @@ const Expr *Expr::skipRValueSubobjectAdj
continue;
}
} else if (const MemberExpr *ME = dyn_cast<MemberExpr>(E)) {
- if (!ME->isArrow() && ME->getBase()->isRValue()) {
+ if (!ME->isArrow()) {
assert(ME->getBase()->getType()->isRecordType());
if (FieldDecl *Field = dyn_cast<FieldDecl>(ME->getMemberDecl())) {
- if (!Field->isBitField()) {
+ if (!Field->isBitField() && !Field->getType()->isReferenceType()) {
E = ME->getBase();
Adjustments.push_back(SubobjectAdjustment(Field));
continue;
Modified: cfe/trunk/lib/Sema/SemaInit.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaInit.cpp?rev=184024&r1=184023&r2=184024&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaInit.cpp (original)
+++ cfe/trunk/lib/Sema/SemaInit.cpp Fri Jun 14 19:30:29 2013
@@ -5236,7 +5236,7 @@ getDeclForTemporaryLifetimeExtension(con
case InitializedEntity::EK_Exception:
case InitializedEntity::EK_VectorElement:
case InitializedEntity::EK_ComplexElement:
- llvm_unreachable("should not materialize a temporary to initialize this");
+ return 0;
}
llvm_unreachable("unknown entity kind");
}
@@ -5245,7 +5245,8 @@ static void performLifetimeExtension(Exp
/// Update a glvalue expression that is used as the initializer of a reference
/// to note that its lifetime is extended.
-static void performReferenceExtension(Expr *Init, const ValueDecl *ExtendingD) {
+/// \return \c true if any temporary had its lifetime extended.
+static bool performReferenceExtension(Expr *Init, const ValueDecl *ExtendingD) {
if (InitListExpr *ILE = dyn_cast<InitListExpr>(Init)) {
if (ILE->getNumInits() == 1 && ILE->isGLValue()) {
// This is just redundant braces around an initializer. Step over it.
@@ -5253,12 +5254,38 @@ static void performReferenceExtension(Ex
}
}
+ // Walk past any constructs which we can lifetime-extend across.
+ Expr *Old;
+ do {
+ Old = Init;
+
+ // Step over any subobject adjustments; we may have a materialized
+ // temporary inside them.
+ SmallVector<const Expr *, 2> CommaLHSs;
+ SmallVector<SubobjectAdjustment, 2> Adjustments;
+ Init = const_cast<Expr *>(
+ Init->skipRValueSubobjectAdjustments(CommaLHSs, Adjustments));
+
+ // Per current approach for DR1376, look through casts to reference type
+ // when performing lifetime extension.
+ if (CastExpr *CE = dyn_cast<CastExpr>(Init))
+ if (CE->getSubExpr()->isGLValue())
+ Init = CE->getSubExpr();
+
+ // FIXME: Per DR1213, subscripting on an array temporary produces an xvalue.
+ // It's unclear if binding a reference to that xvalue extends the array
+ // temporary.
+ } while (Init != Old);
+
if (MaterializeTemporaryExpr *ME = dyn_cast<MaterializeTemporaryExpr>(Init)) {
// Update the storage duration of the materialized temporary.
// FIXME: Rebuild the expression instead of mutating it.
ME->setExtendingDecl(ExtendingD);
performLifetimeExtension(ME->GetTemporaryExpr(), ExtendingD);
+ return true;
}
+
+ return false;
}
/// Update a prvalue expression that is going to be materialized as a
@@ -5274,8 +5301,10 @@ static void performLifetimeExtension(Exp
Init = BTE->getSubExpr();
if (CXXStdInitializerListExpr *ILE =
- dyn_cast<CXXStdInitializerListExpr>(Init))
- return performReferenceExtension(ILE->getSubExpr(), ExtendingD);
+ dyn_cast<CXXStdInitializerListExpr>(Init)) {
+ performReferenceExtension(ILE->getSubExpr(), ExtendingD);
+ return;
+ }
if (InitListExpr *ILE = dyn_cast<InitListExpr>(Init)) {
if (ILE->getType()->isArrayType()) {
@@ -5582,6 +5611,16 @@ InitializationSequence::Perform(Sema &S,
if (S.CheckExceptionSpecCompatibility(CurInit.get(), DestType))
return ExprError();
+ // Even though we didn't materialize a temporary, the binding may still
+ // extend the lifetime of a temporary. This happens if we bind a reference
+ // to the result of a cast to reference type.
+ if (const ValueDecl *ExtendingDecl =
+ getDeclForTemporaryLifetimeExtension(Entity)) {
+ if (performReferenceExtension(CurInit.get(), ExtendingDecl))
+ warnOnLifetimeExtension(S, Entity, CurInit.get(), false,
+ ExtendingDecl);
+ }
+
break;
case SK_BindReferenceToTemporary: {
Modified: cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp?rev=184024&r1=184023&r2=184024&view=diff
==============================================================================
--- cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp (original)
+++ cfe/trunk/test/CXX/expr/expr.prim/expr.prim.lambda/p11-1y.cpp Fri Jun 14 19:30:29 2013
@@ -69,7 +69,7 @@ auto use_multi_return() {
return nm.n + nm.m;
}
-auto a = [a(4), b = 5, &c = static_cast<const int&&>(0)] {
+auto a = [a(4), b = 5, &c = static_cast<const int&&>(0)] { // expected-warning {{binding reference member 'c' to a temporary value}} expected-note {{here}}
static_assert(sizeof(a) == sizeof(int), "");
static_assert(sizeof(b) == sizeof(int), "");
using T = decltype(c);
Modified: cfe/trunk/test/CodeGenCXX/temporaries.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/temporaries.cpp?rev=184024&r1=184023&r2=184024&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/temporaries.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/temporaries.cpp Fri Jun 14 19:30:29 2013
@@ -1,4 +1,32 @@
// RUN: %clang_cc1 -emit-llvm %s -o - -triple=x86_64-apple-darwin9 -std=c++11 | FileCheck %s
+
+namespace PR16263 {
+ const unsigned int n = 1234;
+ extern const int &r = (const int&)n;
+ // CHECK: @_ZGRN7PR162631rE = private constant i32 1234,
+ // CHECK: @_ZN7PR162631rE = constant i32* @_ZGRN7PR162631rE,
+
+ extern const int &s = reinterpret_cast<const int&>(n);
+ // CHECK: @_ZN7PR16263L1nE = internal constant i32 1234, align 4
+ // CHECK: @_ZN7PR162631sE = constant i32* @_ZN7PR16263L1nE, align 8
+
+ struct A { int n; };
+ struct B { int n; };
+ struct C : A, B {};
+ extern const A &&a = (A&&)(A&&)(C&&)(C{});
+ // CHECK: @_ZGRN7PR162631aE = private global {{.*}} zeroinitializer,
+ // CHECK: @_ZN7PR162631aE = constant {{.*}} bitcast ({{.*}}* @_ZGRN7PR162631aE to
+
+ extern const int &&t = ((B&&)C{}).n;
+ // CHECK: @_ZGRN7PR162631tE = private global {{.*}} zeroinitializer,
+ // CHECK: @_ZN7PR162631tE = constant i32* {{.*}}* @_ZGRN7PR162631tE {{.*}} 4
+
+ struct D { double d; C c; };
+ extern const int &&u = (123, static_cast<B&&>(0, ((D&&)D{}).*&D::c).n);
+ // CHECK: @_ZGRN7PR162631uE = private global {{.*}} zeroinitializer
+ // CHECK: @_ZN7PR162631uE = constant i32* {{.*}} @_ZGRN7PR162631uE {{.*}} 12
+}
+
struct A {
A();
~A();
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