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PR23334: Perform semantic checking of lambda capture initialization in the right context.

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Previously we'd try to perform checks on the captures from the middle of
parsing the lambda's body, at the point where we detected that a variable
needed to be captured. This was wrong in a number of subtle ways. In
PR23334, we couldn't correctly handle the list of potential odr-uses
resulting from the capture, and our attempt to recover from that resulted
in a use-after-free.

We now defer building the initialization expression until we leave the lambda
body and return to the enclosing context, where the initialization does the
right thing. This patch only covers lambda-expressions, but we should apply
the same change to blocks and captured statements too.

llvm-svn: 235921
This commit is contained in:
Richard Smith
2015-04-27 21:27:54 +00:00
parent 5b39524313
commit c38498f046
12 changed files with 255 additions and 265 deletions
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187
clang/lib/Sema/SemaLambda.cpp
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@@ -837,7 +837,8 @@ FieldDecl *Sema::buildInitCaptureField(LambdaScopeInfo *LSI, VarDecl *Var) {
}
void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
Declarator &ParamInfo, Scope *CurScope) {
Declarator &ParamInfo,
Scope *CurScope) {
// Determine if we're within a context where we know that the lambda will
// be dependent, because there are template parameters in scope.
bool KnownDependent = false;
@@ -930,12 +931,8 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
PushDeclContext(CurScope, Method);
// Build the lambda scope.
buildLambdaScope(LSI, Method,
Intro.Range,
Intro.Default, Intro.DefaultLoc,
ExplicitParams,
ExplicitResultType,
!Method->isConst());
buildLambdaScope(LSI, Method, Intro.Range, Intro.Default, Intro.DefaultLoc,
ExplicitParams, ExplicitResultType, !Method->isConst());
// C++11 [expr.prim.lambda]p9:
// A lambda-expression whose smallest enclosing scope is a block scope is a
@@ -1137,7 +1134,7 @@ void Sema::ActOnStartOfLambdaDefinition(LambdaIntroducer &Intro,
void Sema::ActOnLambdaError(SourceLocation StartLoc, Scope *CurScope,
bool IsInstantiation) {
LambdaScopeInfo *LSI = getCurLambda();
LambdaScopeInfo *LSI = cast<LambdaScopeInfo>(FunctionScopes.back());
// Leave the expression-evaluation context.
DiscardCleanupsInEvaluationContext();
@@ -1379,10 +1376,109 @@ static void addBlockPointerConversion(Sema &S,
Conversion->setImplicit(true);
Class->addDecl(Conversion);
}
static ExprResult performLambdaVarCaptureInitialization(
Sema &S, LambdaScopeInfo::Capture &Capture,
FieldDecl *Field,
SmallVectorImpl<VarDecl *> &ArrayIndexVars,
SmallVectorImpl<unsigned> &ArrayIndexStarts) {
assert(Capture.isVariableCapture() && "not a variable capture");
auto *Var = Capture.getVariable();
SourceLocation Loc = Capture.getLocation();
// C++11 [expr.prim.lambda]p21:
// When the lambda-expression is evaluated, the entities that
// are captured by copy are used to direct-initialize each
// corresponding non-static data member of the resulting closure
// object. (For array members, the array elements are
// direct-initialized in increasing subscript order.) These
// initializations are performed in the (unspecified) order in
// which the non-static data members are declared.
// C++ [expr.prim.lambda]p12:
// An entity captured by a lambda-expression is odr-used (3.2) in
// the scope containing the lambda-expression.
ExprResult RefResult = S.BuildDeclarationNameExpr(
CXXScopeSpec(), DeclarationNameInfo(Var->getDeclName(), Loc), Var);
if (RefResult.isInvalid())
return ExprError();
Expr *Ref = RefResult.get();
QualType FieldType = Field->getType();
// When the variable has array type, create index variables for each
// dimension of the array. We use these index variables to subscript
// the source array, and other clients (e.g., CodeGen) will perform
// the necessary iteration with these index variables.
//
// FIXME: This is dumb. Add a proper AST representation for array
// copy-construction and use it here.
SmallVector<VarDecl *, 4> IndexVariables;
QualType BaseType = FieldType;
QualType SizeType = S.Context.getSizeType();
ArrayIndexStarts.push_back(ArrayIndexVars.size());
while (const ConstantArrayType *Array
= S.Context.getAsConstantArrayType(BaseType)) {
// Create the iteration variable for this array index.
IdentifierInfo *IterationVarName = nullptr;
{
SmallString<8> Str;
llvm::raw_svector_ostream OS(Str);
OS << "__i" << IndexVariables.size();
IterationVarName = &S.Context.Idents.get(OS.str());
}
VarDecl *IterationVar = VarDecl::Create(
S.Context, S.CurContext, Loc, Loc, IterationVarName, SizeType,
S.Context.getTrivialTypeSourceInfo(SizeType, Loc), SC_None);
IterationVar->setImplicit();
IndexVariables.push_back(IterationVar);
ArrayIndexVars.push_back(IterationVar);
// Create a reference to the iteration variable.
ExprResult IterationVarRef =
S.BuildDeclRefExpr(IterationVar, SizeType, VK_LValue, Loc);
assert(!IterationVarRef.isInvalid() &&
"Reference to invented variable cannot fail!");
IterationVarRef = S.DefaultLvalueConversion(IterationVarRef.get());
assert(!IterationVarRef.isInvalid() &&
"Conversion of invented variable cannot fail!");
// Subscript the array with this iteration variable.
ExprResult Subscript =
S.CreateBuiltinArraySubscriptExpr(Ref, Loc, IterationVarRef.get(), Loc);
if (Subscript.isInvalid())
return ExprError();
Ref = Subscript.get();
BaseType = Array->getElementType();
}
// Construct the entity that we will be initializing. For an array, this
// will be first element in the array, which may require several levels
// of array-subscript entities.
SmallVector<InitializedEntity, 4> Entities;
Entities.reserve(1 + IndexVariables.size());
Entities.push_back(InitializedEntity::InitializeLambdaCapture(
Var->getIdentifier(), FieldType, Loc));
for (unsigned I = 0, N = IndexVariables.size(); I != N; ++I)
Entities.push_back(
InitializedEntity::InitializeElement(S.Context, 0, Entities.back()));
InitializationKind InitKind = InitializationKind::CreateDirect(Loc, Loc, Loc);
InitializationSequence Init(S, Entities.back(), InitKind, Ref);
return Init.Perform(S, Entities.back(), InitKind, Ref);
}
ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
Scope *CurScope,
bool IsInstantiation) {
Scope *CurScope) {
LambdaScopeInfo LSI = *cast<LambdaScopeInfo>(FunctionScopes.back());
ActOnFinishFunctionBody(LSI.CallOperator, Body);
return BuildLambdaExpr(StartLoc, Body->getLocEnd(), &LSI);
}
ExprResult Sema::BuildLambdaExpr(SourceLocation StartLoc, SourceLocation EndLoc,
LambdaScopeInfo *LSI) {
// Collect information from the lambda scope.
SmallVector<LambdaCapture, 4> Captures;
SmallVector<Expr *, 4> CaptureInits;
@@ -1398,7 +1494,6 @@ ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
SmallVector<VarDecl *, 4> ArrayIndexVars;
SmallVector<unsigned, 4> ArrayIndexStarts;
{
LambdaScopeInfo *LSI = getCurLambda();
CallOperator = LSI->CallOperator;
Class = LSI->Lambda;
IntroducerRange = LSI->IntroducerRange;
@@ -1409,8 +1504,20 @@ ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
ArrayIndexVars.swap(LSI->ArrayIndexVars);
ArrayIndexStarts.swap(LSI->ArrayIndexStarts);
CallOperator->setLexicalDeclContext(Class);
Decl *TemplateOrNonTemplateCallOperatorDecl =
CallOperator->getDescribedFunctionTemplate()
? CallOperator->getDescribedFunctionTemplate()
: cast<Decl>(CallOperator);
TemplateOrNonTemplateCallOperatorDecl->setLexicalDeclContext(Class);
Class->addDecl(TemplateOrNonTemplateCallOperatorDecl);
PopExpressionEvaluationContext();
// Translate captures.
for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I) {
auto CurField = Class->field_begin();
for (unsigned I = 0, N = LSI->Captures.size(); I != N; ++I, ++CurField) {
LambdaScopeInfo::Capture From = LSI->Captures[I];
assert(!From.isBlockCapture() && "Cannot capture __block variables");
bool IsImplicit = I >= LSI->NumExplicitCaptures;
@@ -1432,10 +1539,18 @@ ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
}
VarDecl *Var = From.getVariable();
LambdaCaptureKind Kind = From.isCopyCapture()? LCK_ByCopy : LCK_ByRef;
LambdaCaptureKind Kind = From.isCopyCapture() ? LCK_ByCopy : LCK_ByRef;
Captures.push_back(LambdaCapture(From.getLocation(), IsImplicit, Kind,
Var, From.getEllipsisLoc()));
CaptureInits.push_back(From.getInitExpr());
Expr *Init = From.getInitExpr();
if (!Init) {
auto InitResult = performLambdaVarCaptureInitialization(
*this, From, *CurField, ArrayIndexVars, ArrayIndexStarts);
if (InitResult.isInvalid())
return ExprError();
Init = InitResult.get();
}
CaptureInits.push_back(Init);
}
switch (LSI->ImpCaptureStyle) {
@@ -1458,48 +1573,6 @@ ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
}
CaptureDefaultLoc = LSI->CaptureDefaultLoc;
// C++11 [expr.prim.lambda]p4:
// If a lambda-expression does not include a
// trailing-return-type, it is as if the trailing-return-type
// denotes the following type:
//
// Skip for C++1y return type deduction semantics which uses
// different machinery.
// FIXME: Refactor and Merge the return type deduction machinery.
// FIXME: Assumes current resolution to core issue 975.
if (LSI->HasImplicitReturnType && !getLangOpts().CPlusPlus14) {
deduceClosureReturnType(*LSI);
// - if there are no return statements in the
// compound-statement, or all return statements return
// either an expression of type void or no expression or
// braced-init-list, the type void;
if (LSI->ReturnType.isNull()) {
LSI->ReturnType = Context.VoidTy;
}
// Create a function type with the inferred return type.
const FunctionProtoType *Proto
= CallOperator->getType()->getAs<FunctionProtoType>();
QualType FunctionTy = Context.getFunctionType(
LSI->ReturnType, Proto->getParamTypes(), Proto->getExtProtoInfo());
CallOperator->setType(FunctionTy);
}
// C++ [expr.prim.lambda]p7:
// The lambda-expression's compound-statement yields the
// function-body (8.4) of the function call operator [...].
ActOnFinishFunctionBody(CallOperator, Body, IsInstantiation);
CallOperator->setLexicalDeclContext(Class);
Decl *TemplateOrNonTemplateCallOperatorDecl =
CallOperator->getDescribedFunctionTemplate()
? CallOperator->getDescribedFunctionTemplate()
: cast<Decl>(CallOperator);
TemplateOrNonTemplateCallOperatorDecl->setLexicalDeclContext(Class);
Class->addDecl(TemplateOrNonTemplateCallOperatorDecl);
PopExpressionEvaluationContext();
// C++11 [expr.prim.lambda]p6:
// The closure type for a lambda-expression with no lambda-capture
// has a public non-virtual non-explicit const conversion function
@@ -1534,7 +1607,7 @@ ExprResult Sema::ActOnLambdaExpr(SourceLocation StartLoc, Stmt *Body,
Captures,
ExplicitParams, ExplicitResultType,
CaptureInits, ArrayIndexVars,
ArrayIndexStarts, Body->getLocEnd(),
ArrayIndexStarts, EndLoc,
ContainsUnexpandedParameterPack);
if (!CurContext->isDependentContext()) {