// RUN: %clang_cc1 -fsyntax-only -std=c++11 -verify=expected,cxx11,cxx11-17 -pedantic %s
// RUN: %clang_cc1 -fsyntax-only -std=c++17 -verify=expected,cxx11-17,since-cxx17 -pedantic %s
// RUN: %clang_cc1 -fsyntax-only -std=c++20 -verify=expected,since-cxx17 -pedantic %s
struct [[nodiscard]] S {};
// cxx11-warning@-1 {{use of the 'nodiscard' attribute is a C++17 extension}}
S get_s();
S& get_s_ref();
enum [[nodiscard]] E {};
// cxx11-warning@-1 {{use of the 'nodiscard' attribute is a C++17 extension}}
E get_e();
[[nodiscard]] int get_i();
// cxx11-warning@-1 {{use of the 'nodiscard' attribute is a C++17 extension}}
[[nodiscard]] volatile int &get_vi();
// cxx11-warning@-1 {{use of the 'nodiscard' attribute is a C++17 extension}}
void f() {
get_s(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
get_i(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
get_vi(); // 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
get_s_ref();
(void)get_s();
(void)get_i();
(void)get_vi();
(void)get_e();
}
[[nodiscard]] volatile char &(*fp)(); // expected-warning {{'nodiscard' attribute only applies to functions, classes, or enumerations}}
// cxx11-warning@-1 {{use of the 'nodiscard' attribute is a C++17 extension}}
void g() {
fp(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
// OK, warning suppressed.
(void)fp();
}
namespace PR31526 {
typedef E (*fp1)();
typedef S (*fp2)();
typedef S S_alias;
typedef S_alias (*fp3)();
typedef fp2 fp2_alias;
void f() {
fp1 one;
fp2 two;
fp3 three;
fp2_alias four;
one(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
two(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
three(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
four(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
// These are all okay because of the explicit cast to void.
(void)one();
(void)two();
(void)three();
(void)four();
}
} // namespace PR31526
struct [[nodiscard("reason")]] ReasonStruct {};
// cxx11-17-warning@-1 {{use of the 'nodiscard' attribute is a C++20 extension}}
struct LaterReason;
struct [[nodiscard("later reason")]] LaterReason {};
// cxx11-17-warning@-1 {{use of the 'nodiscard' attribute is a C++20 extension}}
ReasonStruct get_reason();
LaterReason get_later_reason();
[[nodiscard("another reason")]] int another_reason();
// cxx11-17-warning@-1 {{use of the 'nodiscard' attribute is a C++20 extension}}
[[nodiscard("conflicting reason")]] int conflicting_reason();
// cxx11-17-warning@-1 {{use of the 'nodiscard' attribute is a C++20 extension}}
[[nodiscard("special reason")]] int conflicting_reason();
// cxx11-17-warning@-1 {{use of the 'nodiscard' attribute is a C++20 extension}}
void cxx20_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}}
}
namespace p1771 {
struct[[nodiscard("Don't throw me away!")]] ConvertTo{};
// cxx11-17-warning@-1 {{use of the 'nodiscard' attribute is a C++20 extension}}
struct S {
[[nodiscard]] S();
// cxx11-warning@-1 {{use of the 'nodiscard' attribute is a C++17 extension}}
[[nodiscard("Don't let that S-Char go!")]] S(char);
// cxx11-17-warning@-1 {{use of the 'nodiscard' attribute is a C++20 extension}}
S(int);
[[gnu::warn_unused_result]] S(double);
operator ConvertTo();
[[nodiscard]] operator int();
// cxx11-warning@-1 {{use of the 'nodiscard' attribute is a C++17 extension}}
[[nodiscard("Don't throw away as a double")]] operator double();
// cxx11-17-warning@-1 {{use of the 'nodiscard' attribute is a C++20 extension}}
};
struct[[nodiscard("Don't throw me away either!")]] Y{};
// cxx11-17-warning@-1 {{use of the 'nodiscard' attribute is a C++20 extension}}
void usage() {
S(); // expected-warning {{ignoring temporary created by a constructor declared with 'nodiscard' attribute}}
S('A'); // expected-warning {{ignoring temporary created by a constructor declared with 'nodiscard' attribute: Don't let that S-Char go!}}
S(1);
S(2.2);
Y(); // expected-warning {{ignoring temporary created by a constructor declared with 'nodiscard' attribute: Don't throw me away either!}}
S s;
ConvertTo{}; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute: Don't throw me away!}}
// AST is different in C++17 mode. Before, a move ctor for ConvertTo is there
// as well, hence the constructor warning.
// since-cxx17-warning@+2 {{ignoring return value of function declared with 'nodiscard' attribute: Don't throw me away!}}
// cxx11-warning@+1 {{ignoring temporary created by a constructor declared with 'nodiscard' attribute: Don't throw me away!}}
(ConvertTo) s;
(int)s; // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
(S)'c'; // expected-warning {{ignoring temporary created by a constructor declared with 'nodiscard' attribute: Don't let that S-Char go!}}
// since-cxx17-warning@+2 {{ignoring return value of function declared with 'nodiscard' attribute: Don't throw me away!}}
// cxx11-warning@+1 {{ignoring temporary created by a constructor declared with 'nodiscard' attribute: Don't throw me away!}}
static_cast<ConvertTo>(s);
static_cast<int>(s); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
static_cast<double>(s); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute: Don't throw away as a double}}
}
} // namespace p1771
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