test/Sema/c2x-maybe_unused.c

// RUN: %clang_cc1 -fsyntax-only -Wunused -std=c2x -verify %s

// This is the latest version of maybe_unused that we support.
_Static_assert(__has_c_attribute(maybe_unused) == 202106L);

struct [[maybe_unused]] S1 { // ok
  int a [[maybe_unused]];
};

enum [[maybe_unused]] E1 {
  EnumVal [[maybe_unused]]
};

[[maybe_unused]] void unused_func([[maybe_unused]] int parm) {
  typedef int maybe_unused_int [[maybe_unused]];
  [[maybe_unused]] int I;
}

void f1(void) {
  int x; // expected-warning {{unused variable}}
  typedef int I; // expected-warning {{unused typedef 'I'}}

  // Should not warn about these due to not being used.
  [[maybe_unused]] int y;
  typedef int maybe_unused_int [[maybe_unused]];

  // Should not warn about these uses.
  struct S1 s;
  maybe_unused_int test;
  y = 12;
}

void f2(void);
[[maybe_unused]] void f2(void);

void f2(void) {
}

void label(void) {
  [[maybe_unused]] label:
  ;

  other_label: // expected-warning {{unused label 'other_label'}}
  ;
}