thakis updated this revision to Diff 48107.
thakis added a comment.
Checkpointing; not production quality. I tried implementing the general DR 253
rule, and this patch mostly does that. It currently walks all fields and all
bases for every const record decl; there should probably be a cache for "are
all fields obviously initialized"; probably on CXXRecordDecl. I had to change
some test cases, but nothing surprising.
However, while this patch does fix `const std::unordered_map<int, int> um;`
with libstdc++5.3, it does _not_ fix `std::vector<int> v;` or `const
std::unordered_map<int, int> um;` when -D_GLIBCXX_DEBUG=1 is passed in.
Investigating that case more now.
http://reviews.llvm.org/D16552
Files:
lib/Sema/SemaInit.cpp
test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p2.cpp
test/CXX/dcl.decl/dcl.init/p6.cpp
test/SemaCXX/attr-selectany.cpp
test/SemaCXX/constexpr-value-init.cpp
test/SemaCXX/cxx0x-cursory-default-delete.cpp
test/SemaCXX/illegal-member-initialization.cpp
Index: test/SemaCXX/illegal-member-initialization.cpp
===================================================================
--- test/SemaCXX/illegal-member-initialization.cpp
+++ test/SemaCXX/illegal-member-initialization.cpp
@@ -7,6 +7,7 @@
};
struct B {
+ int field;
};
struct X {
Index: test/SemaCXX/cxx0x-cursory-default-delete.cpp
===================================================================
--- test/SemaCXX/cxx0x-cursory-default-delete.cpp
+++ test/SemaCXX/cxx0x-cursory-default-delete.cpp
@@ -11,6 +11,7 @@
non_const_copy& operator = (non_const_copy&) &;
non_const_copy& operator = (non_const_copy&) &&;
non_const_copy() = default; // expected-note {{not viable}}
+ int uninit_field;
};
non_const_copy::non_const_copy(non_const_copy&) = default; // expected-note {{not viable}}
non_const_copy& non_const_copy::operator = (non_const_copy&) & = default; // expected-note {{not viable}}
@@ -30,6 +31,56 @@
ncc = cncc; // expected-error {{no viable overloaded}}
};
+struct no_fields { };
+struct all_init {
+ int a = 0;
+ int b = 0;
+};
+struct some_init {
+ int a = 0;
+ int b;
+ int c = 0;
+};
+struct some_init_def {
+ some_init_def() = default;
+ int a = 0;
+ int b;
+ int c = 0;
+};
+struct some_init_ctor {
+ some_init_ctor();
+ int a = 0;
+ int b;
+ int c = 0;
+};
+struct sub_some_init : public some_init_def { };
+struct sub_some_init_ctor : public some_init_def {
+ sub_some_init_ctor();
+};
+struct some_init_container {
+ some_init_def sid;
+};
+struct some_init_container_ctor {
+ some_init_container_ctor();
+ some_init_def sid;
+};
+struct no_fields_container {
+ no_fields nf;
+};
+
+void constobjs() {
+ const no_fields nf; // ok
+ const all_init ai; // ok
+ const some_init si; // expected-error {{default initialization of an object of const type 'const some_init' without a user-provided default constructor}}
+ const some_init_def sid; // expected-error {{default initialization of an object of const type 'const some_init_def' without a user-provided default constructor}}
+ const some_init_ctor sic; // ok
+ const sub_some_init ssi; // expected-error {{default initialization of an object of const type 'const sub_some_init' without a user-provided default constructor}}
+ const sub_some_init_ctor ssic; // ok
+ const some_init_container sicon; // expected-error {{default initialization of an object of const type 'const some_init_container' without a user-provided default constructor}}
+ const some_init_container_ctor siconc; // ok
+ const no_fields_container nfc; // ok
+}
+
struct non_const_derived : non_const_copy {
non_const_derived(const non_const_derived&) = default; // expected-error {{requires it to be non-const}}
non_const_derived& operator =(non_const_derived&) = default;
Index: test/SemaCXX/constexpr-value-init.cpp
===================================================================
--- test/SemaCXX/constexpr-value-init.cpp
+++ test/SemaCXX/constexpr-value-init.cpp
@@ -14,7 +14,7 @@
constexpr A a; // expected-error {{constant expression}} expected-note {{in call to 'A()'}}
}
-constexpr B b1; // expected-error {{without a user-provided default constructor}}
+constexpr B b1; // ok
constexpr B b2 = B(); // ok
static_assert(b2.a.a == 1, "");
static_assert(b2.a.b == 2, "");
Index: test/SemaCXX/attr-selectany.cpp
===================================================================
--- test/SemaCXX/attr-selectany.cpp
+++ test/SemaCXX/attr-selectany.cpp
@@ -39,7 +39,9 @@
// The D3D11 headers do something like this. MSVC doesn't error on this at
// all, even without the __declspec(selectany), in violation of the standard.
// We fall back to a warning for selectany to accept headers.
-struct SomeStruct {};
+struct SomeStruct {
+ int foo;
+};
extern const __declspec(selectany) SomeStruct some_struct; // expected-warning {{default initialization of an object of const type 'const SomeStruct' without a user-provided default constructor is a Microsoft extension}}
// It should be possible to redeclare variables that were defined
Index: test/CXX/dcl.decl/dcl.init/p6.cpp
===================================================================
--- test/CXX/dcl.decl/dcl.init/p6.cpp
+++ test/CXX/dcl.decl/dcl.init/p6.cpp
@@ -4,8 +4,8 @@
// If a program calls for the default initialization of an object of a
// const-qualified type T, T shall be a class type with a
-// user-provided default constructor.
-struct MakeNonPOD { MakeNonPOD(); };
+// user-provided default constructor, except if T has no uninitialized fields.
+struct MakeNonPOD { MakeNonPOD(); int field; };
struct NoUserDefault : public MakeNonPOD { };
struct HasUserDefault { HasUserDefault(); };
@@ -16,7 +16,7 @@
}
// rdar://8501008
-struct s0 {};
+struct s0 { int field; };
struct s1 { static const s0 foo; };
const struct s0 s1::foo; // expected-error{{default initialization of an object of const type 'const struct s0' without a user-provided default constructor}}
Index: test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p2.cpp
===================================================================
--- test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p2.cpp
+++ test/CXX/dcl.decl/dcl.fct.def/dcl.fct.def.default/p2.cpp
@@ -116,6 +116,7 @@
namespace PR13492 {
struct B {
B() = default;
+ int field;
};
void f() {
Index: lib/Sema/SemaInit.cpp
===================================================================
--- lib/Sema/SemaInit.cpp
+++ lib/Sema/SemaInit.cpp
@@ -363,6 +363,15 @@
InitListExpr *getFullyStructuredList() const { return FullyStructuredList; }
};
+bool IsContainedInNamespaceStd(Sema& S, CXXRecordDecl *R) {
+ for (NamespaceDecl *ND = dyn_cast<NamespaceDecl>(R->getDeclContext()); ND;
+ ND = dyn_cast<NamespaceDecl>(ND->getParent())) {
+ if (S.getStdNamespace()->InEnclosingNamespaceSetOf(ND))
+ return true;
+ }
+ return false;
+}
+
} // end anonymous namespace
ExprResult InitListChecker::PerformEmptyInit(Sema &SemaRef,
@@ -422,14 +431,8 @@
if (CtorDecl->getMinRequiredArguments() == 0 &&
CtorDecl->isExplicit() && R->getDeclName() &&
SemaRef.SourceMgr.isInSystemHeader(CtorDecl->getLocation())) {
- bool IsInStd = false;
- for (NamespaceDecl *ND = dyn_cast<NamespaceDecl>(R->getDeclContext());
- ND && !IsInStd; ND = dyn_cast<NamespaceDecl>(ND->getParent())) {
- if (SemaRef.getStdNamespace()->InEnclosingNamespaceSetOf(ND))
- IsInStd = true;
- }
-
- if (IsInStd && llvm::StringSwitch<bool>(R->getName())
+ if (IsContainedInNamespaceStd(SemaRef, R) &&
+ llvm::StringSwitch<bool>(R->getName())
.Cases("basic_string", "deque", "forward_list", true)
.Cases("list", "map", "multimap", "multiset", true)
.Cases("priority_queue", "queue", "set", "stack", true)
@@ -3418,6 +3421,38 @@
return CandidateSet.BestViableFunction(S, DeclLoc, Best);
}
+static bool HasUninitializedFields(const CXXRecordDecl* R) {
+ for (const auto *F : R->fields()) {
+ if (F->hasInClassInitializer() || F->isUnnamedBitfield())
+ continue;
+ if (CXXRecordDecl *FieldType = F->getType()->getAsCXXRecordDecl()) {
+ if (FieldType->hasUserProvidedDefaultConstructor())
+ continue;
+ if (HasUninitializedFields(FieldType)) {
+FieldType->dump();
+ return true;
+ } else {
+ // Has class type but class has no user-provided default ctor. Only
+ // a problem if that class has uninitialized fields.
+ if (!HasUninitializedFields(FieldType))
+ continue;
+ }
+ }
+ // field has no intializer
+ F->dump();
+ return true;
+ }
+ for (const auto& BI : R->bases()) {
+ const RecordType *RT = BI.getType()->getAs<RecordType>();
+ CXXRecordDecl *Base = cast<CXXRecordDecl>(RT->getDecl());
+ if (HasUninitializedFields(Base)) {
+Base->dump();
+ return true;
+ }
+ }
+ return false;
+}
+
/// \brief Attempt initialization by constructor (C++ [dcl.init]), which
/// enumerates the constructors of the initialized entity and performs overload
/// resolution to select the best.
@@ -3515,18 +3550,24 @@
// If a program calls for the default initialization of an object
// of a const-qualified type T, T shall be a class type with a
// user-provided default constructor.
+ CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
if (Kind.getKind() == InitializationKind::IK_Default &&
- Entity.getType().isConstQualified() &&
- !cast<CXXConstructorDecl>(Best->Function)->isUserProvided()) {
- if (!maybeRecoverWithZeroInitialization(S, Sequence, Entity))
- Sequence.SetFailed(InitializationSequence::FK_DefaultInitOfConst);
- return;
+ Entity.getType().isConstQualified() && !CtorDecl->isUserProvided()) {
+ // Some libstdc++ types use `MyType() = default;` which technically isn't
+ // a user-provided default constructor. For types that don't have
+ // uninitialized fields, suppress the error. See also core issue 253.
+ CXXRecordDecl *R = CtorDecl->getParent();
+ bool AllowConstDefaultInit = !HasUninitializedFields(R);
+ if (!AllowConstDefaultInit) {
+ if (!maybeRecoverWithZeroInitialization(S, Sequence, Entity))
+ Sequence.SetFailed(InitializationSequence::FK_DefaultInitOfConst);
+ return;
+ }
}
// C++11 [over.match.list]p1:
// In copy-list-initialization, if an explicit constructor is chosen, the
// initializer is ill-formed.
- CXXConstructorDecl *CtorDecl = cast<CXXConstructorDecl>(Best->Function);
if (IsListInit && !Kind.AllowExplicit() && CtorDecl->isExplicit()) {
Sequence.SetFailed(InitializationSequence::FK_ExplicitConstructor);
return;
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