r363429 - PR23833, DR2140: an lvalue-to-rvalue conversion on a glvalue of type
Richard Smith via cfe-commits
cfe-commits at lists.llvm.org
Fri Jun 14 10:46:38 PDT 2019
Author: rsmith
Date: Fri Jun 14 10:46:38 2019
New Revision: 363429
URL: http://llvm.org/viewvc/llvm-project?rev=363429&view=rev
Log:
PR23833, DR2140: an lvalue-to-rvalue conversion on a glvalue of type
nullptr_t does not access memory.
We now reuse CK_NullToPointer to represent a conversion from a glvalue
of type nullptr_t to a prvalue of nullptr_t where necessary.
This reinstates r363337, reverted in r363352.
Modified:
cfe/trunk/lib/AST/Expr.cpp
cfe/trunk/lib/CodeGen/CGExprAgg.cpp
cfe/trunk/lib/CodeGen/CGExprScalar.cpp
cfe/trunk/lib/Sema/SemaExpr.cpp
cfe/trunk/lib/Sema/SemaInit.cpp
cfe/trunk/lib/StaticAnalyzer/Core/ExprEngineC.cpp
cfe/trunk/test/Analysis/nullptr.cpp
cfe/trunk/test/CXX/drs/dr21xx.cpp
cfe/trunk/test/CodeGenCXX/nullptr.cpp
cfe/trunk/www/cxx_dr_status.html
Modified: cfe/trunk/lib/AST/Expr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=363429&r1=363428&r2=363429&view=diff
==============================================================================
--- cfe/trunk/lib/AST/Expr.cpp (original)
+++ cfe/trunk/lib/AST/Expr.cpp Fri Jun 14 10:46:38 2019
@@ -1885,6 +1885,11 @@ ImplicitCastExpr *ImplicitCastExpr::Crea
ExprValueKind VK) {
unsigned PathSize = (BasePath ? BasePath->size() : 0);
void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier *>(PathSize));
+ // Per C++ [conv.lval]p3, lvalue-to-rvalue conversions on class and
+ // std::nullptr_t have special semantics not captured by CK_LValueToRValue.
+ assert((Kind != CK_LValueToRValue ||
+ !(T->isNullPtrType() || T->getAsCXXRecordDecl())) &&
+ "invalid type for lvalue-to-rvalue conversion");
ImplicitCastExpr *E =
new (Buffer) ImplicitCastExpr(T, Kind, Operand, PathSize, VK);
if (PathSize)
Modified: cfe/trunk/lib/CodeGen/CGExprAgg.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprAgg.cpp?rev=363429&r1=363428&r2=363429&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGExprAgg.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGExprAgg.cpp Fri Jun 14 10:46:38 2019
@@ -1352,7 +1352,8 @@ static bool isSimpleZero(const Expr *E,
// (int*)0 - Null pointer expressions.
if (const CastExpr *ICE = dyn_cast<CastExpr>(E))
return ICE->getCastKind() == CK_NullToPointer &&
- CGF.getTypes().isPointerZeroInitializable(E->getType());
+ CGF.getTypes().isPointerZeroInitializable(E->getType()) &&
+ !E->HasSideEffects(CGF.getContext());
// '\0'
if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E))
return CL->getValue() == 0;
Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprScalar.cpp?rev=363429&r1=363428&r2=363429&view=diff
==============================================================================
--- cfe/trunk/lib/CodeGen/CGExprScalar.cpp (original)
+++ cfe/trunk/lib/CodeGen/CGExprScalar.cpp Fri Jun 14 10:46:38 2019
@@ -2148,14 +2148,14 @@ Value *ScalarExprEmitter::VisitCastExpr(
case CK_NullToPointer:
if (MustVisitNullValue(E))
- (void) Visit(E);
+ CGF.EmitIgnoredExpr(E);
return CGF.CGM.getNullPointer(cast<llvm::PointerType>(ConvertType(DestTy)),
DestTy);
case CK_NullToMemberPointer: {
if (MustVisitNullValue(E))
- (void) Visit(E);
+ CGF.EmitIgnoredExpr(E);
const MemberPointerType *MPT = CE->getType()->getAs<MemberPointerType>();
return CGF.CGM.getCXXABI().EmitNullMemberPointer(MPT);
Modified: cfe/trunk/lib/Sema/SemaExpr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=363429&r1=363428&r2=363429&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaExpr.cpp (original)
+++ cfe/trunk/lib/Sema/SemaExpr.cpp Fri Jun 14 10:46:38 2019
@@ -635,8 +635,10 @@ ExprResult Sema::DefaultLvalueConversion
if (E->getType().getObjCLifetime() == Qualifiers::OCL_Weak)
Cleanup.setExprNeedsCleanups(true);
- Res = ImplicitCastExpr::Create(Context, T, CK_LValueToRValue, E, nullptr,
- VK_RValue);
+ // C++ [conv.lval]p3:
+ // If T is cv std::nullptr_t, the result is a null pointer constant.
+ CastKind CK = T->isNullPtrType() ? CK_NullToPointer : CK_LValueToRValue;
+ Res = ImplicitCastExpr::Create(Context, T, CK, E, nullptr, VK_RValue);
// C11 6.3.2.1p2:
// ... if the lvalue has atomic type, the value has the non-atomic version
Modified: cfe/trunk/lib/Sema/SemaInit.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaInit.cpp?rev=363429&r1=363428&r2=363429&view=diff
==============================================================================
--- cfe/trunk/lib/Sema/SemaInit.cpp (original)
+++ cfe/trunk/lib/Sema/SemaInit.cpp Fri Jun 14 10:46:38 2019
@@ -7779,9 +7779,13 @@ ExprResult InitializationSequence::Perfo
case SK_LValueToRValue: {
assert(CurInit.get()->isGLValue() && "cannot load from a prvalue");
- CurInit = ImplicitCastExpr::Create(S.Context, Step->Type,
- CK_LValueToRValue, CurInit.get(),
- /*BasePath=*/nullptr, VK_RValue);
+ // C++ [conv.lval]p3:
+ // If T is cv std::nullptr_t, the result is a null pointer constant.
+ CastKind CK =
+ Step->Type->isNullPtrType() ? CK_NullToPointer : CK_LValueToRValue;
+ CurInit =
+ ImplicitCastExpr::Create(S.Context, Step->Type, CK, CurInit.get(),
+ /*BasePath=*/nullptr, VK_RValue);
break;
}
Modified: cfe/trunk/lib/StaticAnalyzer/Core/ExprEngineC.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Core/ExprEngineC.cpp?rev=363429&r1=363428&r2=363429&view=diff
==============================================================================
--- cfe/trunk/lib/StaticAnalyzer/Core/ExprEngineC.cpp (original)
+++ cfe/trunk/lib/StaticAnalyzer/Core/ExprEngineC.cpp Fri Jun 14 10:46:38 2019
@@ -378,7 +378,6 @@ void ExprEngine::VisitCast(const CastExp
case CK_BitCast:
case CK_AddressSpaceConversion:
case CK_BooleanToSignedIntegral:
- case CK_NullToPointer:
case CK_IntegralToPointer:
case CK_PointerToIntegral: {
SVal V = state->getSVal(Ex, LCtx);
@@ -503,6 +502,12 @@ void ExprEngine::VisitCast(const CastExp
Bldr.generateNode(CastE, Pred, state);
continue;
}
+ case CK_NullToPointer: {
+ SVal V = svalBuilder.makeNull();
+ state = state->BindExpr(CastE, LCtx, V);
+ Bldr.generateNode(CastE, Pred, state);
+ continue;
+ }
case CK_NullToMemberPointer: {
SVal V = svalBuilder.getMemberPointer(nullptr);
state = state->BindExpr(CastE, LCtx, V);
Modified: cfe/trunk/test/Analysis/nullptr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/nullptr.cpp?rev=363429&r1=363428&r2=363429&view=diff
==============================================================================
--- cfe/trunk/test/Analysis/nullptr.cpp (original)
+++ cfe/trunk/test/Analysis/nullptr.cpp Fri Jun 14 10:46:38 2019
@@ -128,18 +128,10 @@ void shouldNotCrash() {
decltype(nullptr) p; // expected-note{{'p' declared without an initial value}}
if (getSymbol()) // expected-note {{Assuming the condition is false}}
// expected-note at -1{{Taking false branch}}
- // expected-note at -2{{Assuming the condition is false}}
- // expected-note at -3{{Taking false branch}}
- // expected-note at -4{{Assuming the condition is true}}
- // expected-note at -5{{Taking true branch}}
- invokeF(p); // expected-warning{{1st function call argument is an uninitialized value}}
- // expected-note at -1{{1st function call argument is an uninitialized value}}
- if (getSymbol()) // expected-note {{Assuming the condition is false}}
- // expected-note at -1{{Taking false branch}}
// expected-note at -2{{Assuming the condition is true}}
// expected-note at -3{{Taking true branch}}
- invokeF(nullptr); // expected-note {{Calling 'invokeF'}}
- // expected-note at -1{{Passing null pointer value via 1st parameter 'x'}}
+ invokeF(p); // expected-note {{Calling 'invokeF'}}
+ // expected-note at -1{{Passing null pointer value via 1st parameter 'x'}}
if (getSymbol()) { // expected-note {{Assuming the condition is true}}
// expected-note at -1{{Taking true branch}}
X *xx = Type().x; // expected-note {{Null pointer value stored to field 'x'}}
Modified: cfe/trunk/test/CXX/drs/dr21xx.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/drs/dr21xx.cpp?rev=363429&r1=363428&r2=363429&view=diff
==============================================================================
--- cfe/trunk/test/CXX/drs/dr21xx.cpp (original)
+++ cfe/trunk/test/CXX/drs/dr21xx.cpp Fri Jun 14 10:46:38 2019
@@ -32,6 +32,16 @@ namespace dr2120 { // dr2120: 7
static_assert(!__is_standard_layout(E), "");
}
+namespace dr2140 { // dr2140: 9
+#if __cplusplus >= 201103L
+ union U { int a; decltype(nullptr) b; };
+ constexpr int *test(U u) {
+ return u.b;
+ }
+ static_assert(!test({123}), "u.b should be valid even when b is inactive");
+#endif
+}
+
namespace dr2170 { // dr2170: 9
#if __cplusplus >= 201103L
void f() {
Modified: cfe/trunk/test/CodeGenCXX/nullptr.cpp
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/nullptr.cpp?rev=363429&r1=363428&r2=363429&view=diff
==============================================================================
--- cfe/trunk/test/CodeGenCXX/nullptr.cpp (original)
+++ cfe/trunk/test/CodeGenCXX/nullptr.cpp Fri Jun 14 10:46:38 2019
@@ -22,3 +22,50 @@ void g() {
const std::type_info& f2() {
return typeid(nullptr_t);
}
+
+union U {
+ int n;
+ nullptr_t b;
+};
+// CHECK-LABEL: define {{.*}}pr23833_a
+// CHECK: store
+// CHECK: load
+// CHECK-NOT: load
+// CHECK: ret i1 false
+bool pr23833_a(U &u) { return u.b; }
+
+// CHECK-LABEL: define {{.*}}pr23833_b
+// CHECK: store
+// CHECK: load
+// CHECK-NOT: load
+// CHECK: ret i8* null
+nullptr_t pr23833_b(nullptr_t &n) { return n; }
+
+struct X1 { operator int*(); };
+struct X2 { operator const nullptr_t&(); };
+
+// CHECK-LABEL: define {{.*}}pr23833_c
+// CHECK: call {{.*}}X1
+// CHECK: call {{.*}}X2
+// CHECK-NOT: load
+// CHECK: ret i32
+int pr23833_c() {
+ return X1() != X2();
+}
+
+// CHECK-LABEL: define {{.*}}pr23833_d
+// CHECK: call {{.*}}X2
+// CHECK-NOT: load
+// CHECK: store
+// CHECK: load
+// CHECK: ret i32*
+int *pr23833_d() {
+ int *p = X2();
+ return p;
+}
+
+namespace PR39528 {
+ constexpr nullptr_t null = nullptr;
+ void f(nullptr_t);
+ void g() { f(null); }
+}
Modified: cfe/trunk/www/cxx_dr_status.html
URL: http://llvm.org/viewvc/llvm-project/cfe/trunk/www/cxx_dr_status.html?rev=363429&r1=363428&r2=363429&view=diff
==============================================================================
--- cfe/trunk/www/cxx_dr_status.html (original)
+++ cfe/trunk/www/cxx_dr_status.html Fri Jun 14 10:46:38 2019
@@ -12655,7 +12655,7 @@ and <I>POD class</I></td>
<td><a href="http://wg21.link/cwg2140">2140</a></td>
<td>CD4</td>
<td>Lvalue-to-rvalue conversion of <TT>std::nullptr_t</TT></td>
- <td class="none" align="center">Unknown</td>
+ <td class="svn" align="center">SVN</td>
</tr>
<tr id="2141">
<td><a href="http://wg21.link/cwg2141">2141</a></td>
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