The previous implementation would copy the attribute from the class to
functions that have the class as their return type when the functions
are first declared. This proved to have two flaws:
1) if the class is forward-declared without the attribute and a
function or method with the class as a its return type is declared,
and afterward the class is defined with warn_unused_result, the
function or method would never inherit the attribute, and
2) the check simply failed for functions and methods that are part of
a template instantiation, regardless of whether the class with
warn_unused_result is part of a specific instantiation or part of
the template itself (presumably because those function/method
declaration does not hit the same code path as a non-template one
and so never inherits the attribute).
The new approach is to instead modify the two places where a function or
method call is checked for the warn_unused_result attribute on the decl
by extending the checks to also look for the attribute on the decl's
return type.
</commit-message>
I've unified the two locations that performed the check into a helper
method of FunctionDecl that returns true if the decl or its return type
have the warn_unused_result attribute, except if only the return type has
the attribute and the decl is a member of the return type (which avoids
spurious messages on e.g. assignment operators).
Cheers,
Kaelyn
diff --git a/include/clang/AST/Decl.h b/include/clang/AST/Decl.h
index 3e3d79f..f8e1726 100644
--- a/include/clang/AST/Decl.h
+++ b/include/clang/AST/Decl.h
@@ -1965,6 +1965,13 @@ public:
return getType()->getAs<FunctionType>()->getCallResultType(getASTContext());
}
+ /// \brief Returns true if this function or its return type has the
+ /// warn_unused_result attribute. If the return type has the attribute and
+ /// this function is a method of the return type's class, then false will be
+ /// returned to avoid spurious warnings on member methods such as assignment
+ /// operators.
+ bool hasUnusedResultAttr() const;
+
/// \brief Returns the storage class as written in the source. For the
/// computed linkage of symbol, see getLinkage.
StorageClass getStorageClass() const { return StorageClass(SClass); }
diff --git a/lib/AST/Decl.cpp b/lib/AST/Decl.cpp
index ba6fd2e..59d83ff 100644
--- a/lib/AST/Decl.cpp
+++ b/lib/AST/Decl.cpp
@@ -2823,6 +2823,18 @@ SourceRange FunctionDecl::getReturnTypeSourceRange() const {
return RTRange;
}
+bool FunctionDecl::hasUnusedResultAttr() const {
+ QualType RetType = getReturnType();
+ const CXXRecordDecl *Ret = RetType->isRecordType()
+ ? RetType->getAsCXXRecordDecl()
+ : RetType->getPointeeCXXRecordDecl();
+ const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(this);
+ if (Ret && Ret->hasAttr<WarnUnusedResultAttr>() &&
+ !(MD && MD->getCorrespondingMethodInClass(Ret, true)))
+ return true;
+ return hasAttr<WarnUnusedResultAttr>();
+}
+
/// \brief For an inline function definition in C, or for a gnu_inline function
/// in C++, determine whether the definition will be externally visible.
///
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index d13a11c..372d7e9 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -2161,12 +2161,16 @@ bool Expr::isUnusedResultAWarning(const Expr *&WarnE, SourceLocation &Loc,
// If this is a direct call, get the callee.
const CallExpr *CE = cast<CallExpr>(this);
if (const Decl *FD = CE->getCalleeDecl()) {
+ const FunctionDecl *Func = dyn_cast<FunctionDecl>(FD);
+ bool HasWarnUnusedResultAttr = Func ? Func->hasUnusedResultAttr()
+ : FD->hasAttr<WarnUnusedResultAttr>();
+
// If the callee has attribute pure, const, or warn_unused_result, warn
// about it. void foo() { strlen("bar"); } should warn.
//
// Note: If new cases are added here, DiagnoseUnusedExprResult should be
// updated to match for QoI.
- if (FD->hasAttr<WarnUnusedResultAttr>() ||
+ if (HasWarnUnusedResultAttr ||
FD->hasAttr<PureAttr>() || FD->hasAttr<ConstAttr>()) {
WarnE = this;
Loc = CE->getCallee()->getLocStart();
diff --git a/lib/Sema/SemaDecl.cpp b/lib/Sema/SemaDecl.cpp
index ce183d0..1bad38f 100644
--- a/lib/Sema/SemaDecl.cpp
+++ b/lib/Sema/SemaDecl.cpp
@@ -7489,23 +7489,10 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
// Handle attributes.
ProcessDeclAttributes(S, NewFD, D);
- QualType RetType = NewFD->getReturnType();
- const CXXRecordDecl *Ret = RetType->isRecordType() ?
- RetType->getAsCXXRecordDecl() : RetType->getPointeeCXXRecordDecl();
- if (!NewFD->isInvalidDecl() && !NewFD->hasAttr<WarnUnusedResultAttr>() &&
- Ret && Ret->hasAttr<WarnUnusedResultAttr>()) {
- const CXXMethodDecl *MD = dyn_cast<CXXMethodDecl>(NewFD);
- // Attach WarnUnusedResult to functions returning types with that attribute.
- // Don't apply the attribute to that type's own non-static member functions
- // (to avoid warning on things like assignment operators)
- if (!MD || MD->getParent() != Ret)
- NewFD->addAttr(WarnUnusedResultAttr::CreateImplicit(Context));
- }
-
if (getLangOpts().OpenCL) {
// OpenCL v1.1 s6.5: Using an address space qualifier in a function return
// type declaration will generate a compilation error.
- unsigned AddressSpace = RetType.getAddressSpace();
+ unsigned AddressSpace = NewFD->getReturnType().getAddressSpace();
if (AddressSpace == LangAS::opencl_local ||
AddressSpace == LangAS::opencl_global ||
AddressSpace == LangAS::opencl_constant) {
diff --git a/lib/Sema/SemaStmt.cpp b/lib/Sema/SemaStmt.cpp
index 0ac9c89..b491f9f 100644
--- a/lib/Sema/SemaStmt.cpp
+++ b/lib/Sema/SemaStmt.cpp
@@ -236,7 +236,9 @@ void Sema::DiagnoseUnusedExprResult(const Stmt *S) {
// is written in a macro body, only warn if it has the warn_unused_result
// attribute.
if (const Decl *FD = CE->getCalleeDecl()) {
- if (FD->hasAttr<WarnUnusedResultAttr>()) {
+ const FunctionDecl *Func = dyn_cast<FunctionDecl>(FD);
+ if (Func ? Func->hasUnusedResultAttr()
+ : FD->hasAttr<WarnUnusedResultAttr>()) {
Diag(Loc, diag::warn_unused_result) << R1 << R2;
return;
}
diff --git a/test/SemaCXX/warn-unused-result.cpp b/test/SemaCXX/warn-unused-result.cpp
index 7bdb424..88727c5 100644
--- a/test/SemaCXX/warn-unused-result.cpp
+++ b/test/SemaCXX/warn-unused-result.cpp
@@ -44,6 +44,12 @@ void bah() {
}
namespace warn_unused_CXX11 {
+class Status;
+class Foo {
+ public:
+ Status doStuff();
+};
+
struct [[clang::warn_unused_result]] Status {
bool ok() const;
Status& operator=(const Status& x);
@@ -77,6 +83,19 @@ void lazy() {
DoAnotherThing(); // expected-warning {{ignoring return value}}
DoYetAnotherThing();
}
+
+template <typename T>
+class [[clang::warn_unused_result]] StatusOr {
+};
+StatusOr<int> doit();
+void test() {
+ Foo f;
+ f.doStuff(); // expected-warning {{ignoring return value}}
+ doit(); // expected-warning {{ignoring return value}}
+
+ auto func = []() { return Status(); };
+ func(); // expected-warning {{ignoring return value}}
+}
}
namespace PR17587 {
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