erik.pilkington created this revision.
Previously, clang rejected the following (copied from PR19741):
struct A {
int a = 0;
constexpr A() { a = 1; }
};
constexpr bool f() {
constexpr A a;
static_assert(a.a == 1, "");
return a.a == 1;
}
static_assert(f(), "");
Clang didn't like the assignment to `a` in `A()` because it doesn't know that A
is being constructed and therefore considers the subobject A.a to be const. The
fix in this patch (which @rsmith suggested in the PR) is just to keep track of
the set of objects that are currently being constructed, and strip away the
const whenever we encounter a subobject of an object under construction.
https://bugs.llvm.org/show_bug.cgi?id=19741
Thanks for taking a look!
Erik
https://reviews.llvm.org/D38483
Files:
lib/AST/ExprConstant.cpp
test/SemaCXX/constant-expression-cxx1y.cpp
Index: test/SemaCXX/constant-expression-cxx1y.cpp
===================================================================
--- test/SemaCXX/constant-expression-cxx1y.cpp
+++ test/SemaCXX/constant-expression-cxx1y.cpp
@@ -988,3 +988,36 @@
void();
}
constexpr int void_test = (Void(0), 1);
+
+namespace PR19741 {
+constexpr void addone(int &m) { m++; }
+
+struct S {
+ int m = 0;
+ constexpr S() { addone(m); }
+};
+constexpr bool evalS() {
+ constexpr S s;
+ return s.m == 1;
+}
+static_assert(evalS(), "");
+
+struct Nested {
+ struct First { int x = 42; };
+ union {
+ First first;
+ int second;
+ };
+ int x;
+ constexpr Nested(int x) : first(), x(x) { x = 4; }
+ constexpr Nested() : Nested(42) {
+ addone(first.x);
+ x = 3;
+ }
+};
+constexpr bool evalNested() {
+ constexpr Nested N;
+ return N.first.x == 43;
+}
+static_assert(evalNested(), "");
+} // namespace PR19741
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -573,6 +573,30 @@
/// declaration whose initializer is being evaluated, if any.
APValue *EvaluatingDeclValue;
+ typedef std::pair<APValue::LValueBase, unsigned> EvaluatingObject;
+
+ /// EvaluatingConstructors - Set of objects that are currently being
+ /// constructed.
+ llvm::DenseSet<EvaluatingObject> EvaluatingConstructors;
+
+ struct EvaluatingConstructorRAII {
+ EvalInfo &EI;
+ EvaluatingObject Object;
+ bool DidInsert;
+ EvaluatingConstructorRAII(EvalInfo &EI, EvaluatingObject Object)
+ : EI(EI), Object(Object) {
+ DidInsert = EI.EvaluatingConstructors.insert(Object).second;
+ }
+ ~EvaluatingConstructorRAII() {
+ if (DidInsert) EI.EvaluatingConstructors.erase(Object);
+ }
+ };
+
+ bool isEvaluatingConstructor(APValue::LValueBase Decl, unsigned CallIndex)
{
+ return Decl == EvaluatingDecl ||
+ EvaluatingConstructors.count(EvaluatingObject(Decl, CallIndex));
+ }
+
/// The current array initialization index, if we're performing array
/// initialization.
uint64_t ArrayInitIndex = -1;
@@ -3101,7 +3125,7 @@
// FIXME: We don't set up EvaluatingDecl for local variables or temporaries,
// and this doesn't do quite the right thing for const subobjects of the
// object under construction.
- if (LVal.getLValueBase() == Info.EvaluatingDecl) {
+ if (Info.isEvaluatingConstructor(LVal.getLValueBase(), LVal.CallIndex)) {
BaseType = Info.Ctx.getCanonicalType(BaseType);
BaseType.removeLocalConst();
}
@@ -4254,6 +4278,8 @@
return false;
}
+ EvalInfo::EvaluatingConstructorRAII EvalObj(
+ Info, {This.getLValueBase(), This.CallIndex});
CallStackFrame Frame(Info, CallLoc, Definition, &This, ArgValues);
// FIXME: Creating an APValue just to hold a nonexistent return value is
Index: test/SemaCXX/constant-expression-cxx1y.cpp
===================================================================
--- test/SemaCXX/constant-expression-cxx1y.cpp
+++ test/SemaCXX/constant-expression-cxx1y.cpp
@@ -988,3 +988,36 @@
void();
}
constexpr int void_test = (Void(0), 1);
+
+namespace PR19741 {
+constexpr void addone(int &m) { m++; }
+
+struct S {
+ int m = 0;
+ constexpr S() { addone(m); }
+};
+constexpr bool evalS() {
+ constexpr S s;
+ return s.m == 1;
+}
+static_assert(evalS(), "");
+
+struct Nested {
+ struct First { int x = 42; };
+ union {
+ First first;
+ int second;
+ };
+ int x;
+ constexpr Nested(int x) : first(), x(x) { x = 4; }
+ constexpr Nested() : Nested(42) {
+ addone(first.x);
+ x = 3;
+ }
+};
+constexpr bool evalNested() {
+ constexpr Nested N;
+ return N.first.x == 43;
+}
+static_assert(evalNested(), "");
+} // namespace PR19741
Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -573,6 +573,30 @@
/// declaration whose initializer is being evaluated, if any.
APValue *EvaluatingDeclValue;
+ typedef std::pair<APValue::LValueBase, unsigned> EvaluatingObject;
+
+ /// EvaluatingConstructors - Set of objects that are currently being
+ /// constructed.
+ llvm::DenseSet<EvaluatingObject> EvaluatingConstructors;
+
+ struct EvaluatingConstructorRAII {
+ EvalInfo &EI;
+ EvaluatingObject Object;
+ bool DidInsert;
+ EvaluatingConstructorRAII(EvalInfo &EI, EvaluatingObject Object)
+ : EI(EI), Object(Object) {
+ DidInsert = EI.EvaluatingConstructors.insert(Object).second;
+ }
+ ~EvaluatingConstructorRAII() {
+ if (DidInsert) EI.EvaluatingConstructors.erase(Object);
+ }
+ };
+
+ bool isEvaluatingConstructor(APValue::LValueBase Decl, unsigned CallIndex) {
+ return Decl == EvaluatingDecl ||
+ EvaluatingConstructors.count(EvaluatingObject(Decl, CallIndex));
+ }
+
/// The current array initialization index, if we're performing array
/// initialization.
uint64_t ArrayInitIndex = -1;
@@ -3101,7 +3125,7 @@
// FIXME: We don't set up EvaluatingDecl for local variables or temporaries,
// and this doesn't do quite the right thing for const subobjects of the
// object under construction.
- if (LVal.getLValueBase() == Info.EvaluatingDecl) {
+ if (Info.isEvaluatingConstructor(LVal.getLValueBase(), LVal.CallIndex)) {
BaseType = Info.Ctx.getCanonicalType(BaseType);
BaseType.removeLocalConst();
}
@@ -4254,6 +4278,8 @@
return false;
}
+ EvalInfo::EvaluatingConstructorRAII EvalObj(
+ Info, {This.getLValueBase(), This.CallIndex});
CallStackFrame Frame(Info, CallLoc, Definition, &This, ArgValues);
// FIXME: Creating an APValue just to hold a nonexistent return value is
_______________________________________________
cfe-commits mailing list
cfe-commits@lists.llvm.org
http://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
