clang/test/SemaCXX/attr-weak.cpp

   1 // RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -fsyntax-only -verify -std=c++11 %s
   2
   3 static int test0 __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
   4 static void test1() __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
   5
   6 namespace test2 __attribute__((weak)) { // expected-warning {{'weak' attribute only applies to variables, functions, and classes}}
   7 }
   8
   9 namespace {
  10   int test3 __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
  11   void test4() __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
  12 }
  13
  14 struct Test5 {
  15   static void test5() __attribute__((weak)); // no error
  16 };
  17
  18 namespace {
  19   struct Test6 {
  20     static void test6() __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
  21   };
  22 }
  23
  24 // GCC rejects the instantiation with the internal type, but some existing
  25 // code expects it. It is also not that different from giving hidden visibility
  26 // to parts of a template that have explicit default visibility, so we accept
  27 // this.
  28 template <class T> struct Test7 {
  29   void test7() __attribute__((weak)) {}
  30   static int var __attribute__((weak));
  31 };
  32 template <class T>
  33 int Test7<T>::var;
  34 namespace { class Internal {}; }
  35 template struct Test7<Internal>;
  36 template struct Test7<int>;
  37
  38 class __attribute__((weak)) Test8 {}; // OK
  39
  40 __attribute__((weak)) auto Test9 = Internal(); // expected-error {{weak declaration cannot have internal linkage}}
  41
  42 [[gnu::weak]] void weak_function();
  43 struct WithWeakMember {
  44   [[gnu::weak]] void weak_method();
  45   [[gnu::weak]] virtual void virtual_weak_method();
  46 };
  47 constexpr bool weak_function_is_non_null = &weak_function != nullptr; // expected-error {{must be initialized by a constant expression}}
  48 // expected-note@-1 {{comparison against address of weak declaration '&weak_function' can only be performed at runtime}}
  49 constexpr bool weak_method_is_non_null = &WithWeakMember::weak_method != nullptr; // expected-error {{must be initialized by a constant expression}}
  50 // expected-note@-1 {{comparison against pointer to weak member 'WithWeakMember::weak_method' can only be performed at runtime}}
  51 // GCC accepts this and says the result is always non-null. That's consistent
  52 // with the ABI rules for member pointers, but seems unprincipled, so we do not
  53 // follow it for now.
  54 // TODO: Consider warning on such comparisons, as they do not test whether the
  55 // virtual member function is present.
  56 constexpr bool virtual_weak_method_is_non_null = &WithWeakMember::virtual_weak_method != nullptr; // expected-error {{must be initialized by a constant expression}}
  57 // expected-note@-1 {{comparison against pointer to weak member 'WithWeakMember::virtual_weak_method' can only be performed at runtime}}