This also bumps the attribute feature test value and introduces the notion of a C++2a extension warning.
llvm-svn: 366626
}
def WarnUnusedResult : InheritableAttr {
- let Spellings = [CXX11<"", "nodiscard", 201603>, C2x<"", "nodiscard">,
+ let Spellings = [CXX11<"", "nodiscard", 201907>, C2x<"", "nodiscard">,
CXX11<"clang", "warn_unused_result">,
GCC<"warn_unused_result">];
let Subjects = SubjectList<[ObjCMethod, Enum, Record, FunctionLike]>;
+ let Args = [StringArgument<"Message", 1>];
let Documentation = [WarnUnusedResultsDocs];
}
potentially-evaluated discarded-value expression that is not explicitly cast to
`void`.
+A string literal may optionally be provided to the attribute, which will be
+reproduced in any resulting diagnostics. Redeclarations using different forms
+of the attribute (with or without the string literal or with different string
+literal contents) are allowed. If there are redeclarations of the entity with
+differing string literals, it is unspecified which one will be used by Clang
+in any resulting diagnostics.
+
.. code-block: c++
struct [[nodiscard]] error_info { /*...*/ };
error_info enable_missile_safety_mode();
def warn_unused_result : Warning<
"ignoring return value of function declared with %0 attribute">,
InGroup<UnusedResult>;
+def warn_unused_result_msg : Warning<
+ "ignoring return value of function declared with %0 attribute: %1">,
+ InGroup<UnusedResult>;
def warn_unused_volatile : Warning<
"expression result unused; assign into a variable to force a volatile load">,
InGroup<DiagGroup<"unused-volatile-lvalue">>;
"use of the %0 attribute is a C++14 extension">, InGroup<CXX14>;
def ext_cxx17_attr : Extension<
"use of the %0 attribute is a C++17 extension">, InGroup<CXX17>;
+def ext_cxx2a_attr : Extension<
+ "use of the %0 attribute is a C++2a extension">, InGroup<CXX2a>;
def warn_unused_comparison : Warning<
"%select{equality|inequality|relational|three-way}0 comparison result unused">,
return;
}
- // If this is spelled as the standard C++17 attribute, but not in C++17, warn
- // about using it as an extension.
- if (!S.getLangOpts().CPlusPlus17 && AL.isCXX11Attribute() &&
- !AL.getScopeName())
- S.Diag(AL.getLoc(), diag::ext_cxx17_attr) << AL;
+ StringRef Str;
+ if ((AL.isCXX11Attribute() || AL.isC2xAttribute()) && !AL.getScopeName()) {
+ // If this is spelled as the standard C++17 attribute, but not in C++17,
+ // warn about using it as an extension. If there are attribute arguments,
+ // then claim it's a C++2a extension instead.
+ // FIXME: If WG14 does not seem likely to adopt the same feature, add an
+ // extension warning for C2x mode.
+ const LangOptions &LO = S.getLangOpts();
+ if (AL.getNumArgs() == 1) {
+ if (LO.CPlusPlus && !LO.CPlusPlus2a)
+ S.Diag(AL.getLoc(), diag::ext_cxx2a_attr) << AL;
+
+ // Since this this is spelled [[nodiscard]], get the optional string
+ // literal. If in C++ mode, but not in C++2a mode, diagnose as an
+ // extension.
+ // FIXME: C2x should support this feature as well, even as an extension.
+ if (!S.checkStringLiteralArgumentAttr(AL, 0, Str, nullptr))
+ return;
+ } else if (LO.CPlusPlus && !LO.CPlusPlus17)
+ S.Diag(AL.getLoc(), diag::ext_cxx17_attr) << AL;
+ }
D->addAttr(::new (S.Context)
- WarnUnusedResultAttr(AL.getRange(), S.Context,
+ WarnUnusedResultAttr(AL.getRange(), S.Context, Str,
AL.getAttributeSpellingListIndex()));
}
if (E->getType()->isVoidType())
return;
- if (const Attr *A = CE->getUnusedResultAttr(Context)) {
- Diag(Loc, diag::warn_unused_result) << A << R1 << R2;
+ if (const auto *A = cast_or_null<WarnUnusedResultAttr>(
+ CE->getUnusedResultAttr(Context))) {
+ StringRef Msg = A->getMessage();
+ if (!Msg.empty())
+ Diag(Loc, diag::warn_unused_result_msg) << A << Msg << R1 << R2;
+ else
+ Diag(Loc, diag::warn_unused_result) << A << R1 << R2;
return;
}
const ObjCMethodDecl *MD = ME->getMethodDecl();
if (MD) {
if (const auto *A = MD->getAttr<WarnUnusedResultAttr>()) {
- Diag(Loc, diag::warn_unused_result) << A << R1 << R2;
+ StringRef Msg = A->getMessage();
+ if (!Msg.empty())
+ Diag(Loc, diag::warn_unused_result_msg) << A << Msg << R1 << R2;
+ else
+ Diag(Loc, diag::warn_unused_result) << A << R1 << R2;
return;
}
}
-// RUN: %clang_cc1 -fsyntax-only -std=c++1z -verify %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++2a -verify %s
struct [[nodiscard]] S1 {}; // ok
struct [[nodiscard nodiscard]] S2 {}; // expected-error {{attribute 'nodiscard' cannot appear multiple times in an attribute specifier}}
-struct [[nodiscard("Wrong")]] S3 {}; // expected-error {{'nodiscard' cannot have an argument list}}
+struct [[nodiscard("Wrong")]] S3 {};
[[nodiscard]] int f();
enum [[nodiscard]] E {};
+// RUN: %clang_cc1 -fsyntax-only -std=c++2a -verify -Wc++2a-extensions %s
// RUN: %clang_cc1 -fsyntax-only -std=c++17 -verify -Wc++17-extensions %s
-// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify -DEXT -Wc++17-extensions %s
+// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify -DEXT -Wc++17-extensions -Wc++2a-extensions %s
struct [[nodiscard]] S {};
S get_s();
}
} // namespace PR31526
+struct [[nodiscard("reason")]] ReasonStruct {};
+struct LaterReason;
+struct [[nodiscard("later reason")]] LaterReason {};
+
+ReasonStruct get_reason();
+LaterReason get_later_reason();
+[[nodiscard("another reason")]] int another_reason();
+
+[[nodiscard("conflicting reason")]] int conflicting_reason();
+[[nodiscard("special reason")]] int conflicting_reason();
+
+void cxx2a_use() {
+ get_reason(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute: reason}}
+ get_later_reason(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute: later reason}}
+ another_reason(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute: another reason}}
+ conflicting_reason(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute: special reason}}
+}
+
#ifdef EXT
-// expected-warning@4 {{use of the 'nodiscard' attribute is a C++17 extension}}
-// expected-warning@8 {{use of the 'nodiscard' attribute is a C++17 extension}}
-// expected-warning@11 {{use of the 'nodiscard' attribute is a C++17 extension}}
+// expected-warning@5 {{use of the 'nodiscard' attribute is a C++17 extension}}
+// expected-warning@9 {{use of the 'nodiscard' attribute is a C++17 extension}}
// expected-warning@12 {{use of the 'nodiscard' attribute is a C++17 extension}}
-// expected-warning@28 {{use of the 'nodiscard' attribute is a C++17 extension}}
+// expected-warning@13 {{use of the 'nodiscard' attribute is a C++17 extension}}
+// expected-warning@29 {{use of the 'nodiscard' attribute is a C++17 extension}}
+// expected-warning@65 {{use of the 'nodiscard' attribute is a C++2a extension}}
+// expected-warning@67 {{use of the 'nodiscard' attribute is a C++2a extension}}
+// expected-warning@71 {{use of the 'nodiscard' attribute is a C++2a extension}}
+// expected-warning@73 {{use of the 'nodiscard' attribute is a C++2a extension}}
+// expected-warning@74 {{use of the 'nodiscard' attribute is a C++2a extension}}
#endif
// CHECK: maybe_unused: 201603L
// ITANIUM: no_unique_address: 201803L
// WINDOWS: no_unique_address: 0
-// CHECK: nodiscard: 201603L
+// CHECK: nodiscard: 201907L
// CHECK: noreturn: 200809L
// FIXME(201803L) CHECK: unlikely: 0
struct [[nodiscard nodiscard]] S2 { // expected-error {{attribute 'nodiscard' cannot appear multiple times in an attribute specifier}}
int i;
};
-struct [[nodiscard("Wrong")]] S3 { // expected-error {{'nodiscard' cannot have an argument list}}
+struct [[nodiscard("Wrong")]] S3 { // FIXME: may need an extension warning.
int i;
};
+struct S3 get_s3(void);
+
[[nodiscard]] int f1(void);
enum [[nodiscard]] E1 { One };
void f2(void) {
get_s(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+ get_s3(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute: Wrong}}
get_i(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
get_e(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
// Okay, warnings are not encouraged
(void)get_s();
+ (void)get_s3();
(void)get_i();
(void)get_e();
}
// CHECK: void bar() __attribute__((__const));
void bar() __attribute__((__const));
-// CHECK: int f1() __attribute__((warn_unused_result));
+// FIXME: It's unfortunate that the string literal prints with the below three
+// cases given that the string is only exposed via the [[nodiscard]] spelling.
+// CHECK: int f1() __attribute__((warn_unused_result("")));
int f1() __attribute__((warn_unused_result));
-// CHECK: {{\[}}[clang::warn_unused_result]];
+// CHECK: {{\[}}[clang::warn_unused_result("")]];
int f2 [[clang::warn_unused_result]] ();
-// CHECK: {{\[}}[gnu::warn_unused_result]];
+// CHECK: {{\[}}[gnu::warn_unused_result("")]];
int f3 [[gnu::warn_unused_result]] ();
// FIXME: ast-print need to print C++11