Enable support for the [[nodiscard]] attribute from WG14 N2050 when enabling double square bracket attributes in C code.

llvm-svn: 316026

1 files changed, 49 insertions, 0 deletions

diff --git a/clang/test/Sema/c2x-nodiscard.c b/clang/test/Sema/c2x-nodiscard.c
new file mode 100644
index 00000000000..f128d3bb572
--- /dev/null
+++ b/clang/test/Sema/c2x-nodiscard.c
@@ -0,0 +1,49 @@
+// RUN: %clang_cc1 -fsyntax-only -fdouble-square-bracket-attributes -verify %s
+
+struct [[nodiscard]] S1 { // ok
+  int i;
+};
+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}}
+  int i;
+};
+
+[[nodiscard]] int f1(void);
+enum [[nodiscard]] E1 { One };
+
+[[nodiscard]] int i; // expected-warning {{'nodiscard' attribute only applies to functions, methods, enums, and classes}}
+
+struct [[nodiscard]] S4 {
+  int i;
+};
+struct S4 get_s(void);
+
+enum [[nodiscard]] E2 { Two };
+enum E2 get_e(void);
+
+[[nodiscard]] int get_i();
+
+void f2(void) {
+  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_e(); // expected-warning {{ignoring return value of function declared with 'nodiscard' attribute}}
+
+  // Okay, warnings are not encouraged
+  (void)get_s();
+  (void)get_i();
+  (void)get_e();
+}
+
+struct [[nodiscard]] error_info{
+  int i;
+};
+
+struct error_info enable_missile_safety_mode(void);
+void launch_missiles(void);
+void test_missiles(void) {
+  enable_missile_safety_mode(); // expected-warning {{ignoring return value of function declared with 'nodiscard'}}
+  launch_missiles();
+}
+