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[LifetimeAnalysis] Fix PR44150

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References need somewhat special treatment. While copying a gsl::Pointer
will propagate the points-to set, creating an object from a reference
often behaves more like a dereference operation.

Differential Revision: https://reviews.llvm.org/D70755
This commit is contained in:
Gabor Horvath 2019-11-27 09:08:51 -08:00
parent 3d9b1128d6
commit bcd0798c47
2 changed files with 31 additions and 7 deletions
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33
clang/lib/Sema/SemaInit.cpp
View File

@ -6653,6 +6653,7 @@ struct IndirectLocalPathEntry {
VarInit,
LValToRVal,
LifetimeBoundCall,
GslReferenceInit,
GslPointerInit
} Kind;
Expr *E;
@ -6783,12 +6784,24 @@ static bool shouldTrackFirstArgument(const FunctionDecl *FD) {
static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call,
LocalVisitor Visit) {
auto VisitPointerArg = [&](const Decl *D, Expr *Arg) {
auto VisitPointerArg = [&](const Decl *D, Expr *Arg, bool Value) {
// We are not interested in the temporary base objects of gsl Pointers:
// Temp().ptr; // Here ptr might not dangle.
if (isa<MemberExpr>(Arg->IgnoreImpCasts()))
return;
Path.push_back({IndirectLocalPathEntry::GslPointerInit, Arg, D});
// Once we initialized a value with a reference, it can no longer dangle.
if (!Value) {
for (auto It = Path.rbegin(), End = Path.rend(); It != End; ++It) {
if (It->Kind == IndirectLocalPathEntry::GslReferenceInit)
continue;
if (It->Kind == IndirectLocalPathEntry::GslPointerInit)
return;
break;
}
}
Path.push_back({Value ? IndirectLocalPathEntry::GslPointerInit
: IndirectLocalPathEntry::GslReferenceInit,
Arg, D});
if (Arg->isGLValue())
visitLocalsRetainedByReferenceBinding(Path, Arg, RK_ReferenceBinding,
Visit,
@ -6802,18 +6815,21 @@ static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call,
if (auto *MCE = dyn_cast<CXXMemberCallExpr>(Call)) {
const auto *MD = cast_or_null<CXXMethodDecl>(MCE->getDirectCallee());
if (MD && shouldTrackImplicitObjectArg(MD))
VisitPointerArg(MD, MCE->getImplicitObjectArgument());
VisitPointerArg(MD, MCE->getImplicitObjectArgument(),
!MD->getReturnType()->isReferenceType());
return;
} else if (auto *OCE = dyn_cast<CXXOperatorCallExpr>(Call)) {
FunctionDecl *Callee = OCE->getDirectCallee();
if (Callee && Callee->isCXXInstanceMember() &&
shouldTrackImplicitObjectArg(cast<CXXMethodDecl>(Callee)))
VisitPointerArg(Callee, OCE->getArg(0));
VisitPointerArg(Callee, OCE->getArg(0),
!Callee->getReturnType()->isReferenceType());
return;
} else if (auto *CE = dyn_cast<CallExpr>(Call)) {
FunctionDecl *Callee = CE->getDirectCallee();
if (Callee && shouldTrackFirstArgument(Callee))
VisitPointerArg(Callee, CE->getArg(0));
VisitPointerArg(Callee, CE->getArg(0),
!Callee->getReturnType()->isReferenceType());
return;
}
@ -6821,7 +6837,7 @@ static void handleGslAnnotatedTypes(IndirectLocalPath &Path, Expr *Call,
const auto *Ctor = CCE->getConstructor();
const CXXRecordDecl *RD = Ctor->getParent();
if (CCE->getNumArgs() > 0 && RD->hasAttr<PointerAttr>())
VisitPointerArg(Ctor->getParamDecl(0), CCE->getArgs()[0]);
VisitPointerArg(Ctor->getParamDecl(0), CCE->getArgs()[0], true);
}
}
@ -7287,6 +7303,7 @@ static SourceRange nextPathEntryRange(const IndirectLocalPath &Path, unsigned I,
case IndirectLocalPathEntry::AddressOf:
case IndirectLocalPathEntry::LValToRVal:
case IndirectLocalPathEntry::LifetimeBoundCall:
case IndirectLocalPathEntry::GslReferenceInit:
case IndirectLocalPathEntry::GslPointerInit:
// These exist primarily to mark the path as not permitting or
// supporting lifetime extension.
@ -7309,7 +7326,8 @@ static bool pathOnlyInitializesGslPointer(IndirectLocalPath &Path) {
continue;
if (It->Kind == IndirectLocalPathEntry::AddressOf)
continue;
return It->Kind == IndirectLocalPathEntry::GslPointerInit;
return It->Kind == IndirectLocalPathEntry::GslPointerInit ||
It->Kind == IndirectLocalPathEntry::GslReferenceInit;
}
return false;
}
@ -7532,6 +7550,7 @@ void Sema::checkInitializerLifetime(const InitializedEntity &Entity,
case IndirectLocalPathEntry::LifetimeBoundCall:
case IndirectLocalPathEntry::GslPointerInit:
case IndirectLocalPathEntry::GslReferenceInit:
// FIXME: Consider adding a note for these.
break;

5
clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
View File

@ -450,3 +450,8 @@ MyIntPointer handleDerivedToBaseCast1(MySpecialIntPointer ptr) {
MyIntPointer handleDerivedToBaseCast2(MyOwnerIntPointer ptr) {
return ptr; // expected-warning {{address of stack memory associated with parameter 'ptr' returned}}
}
std::vector<int>::iterator noFalsePositiveWithVectorOfPointers() {
std::vector<std::vector<int>::iterator> iters;
return iters.at(0);
}