clang/test/SemaCXX/attr-weak.cpp

   1 // RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -fsyntax-only -verify -std=c++11 %s
   2 // RUN: %clang_cc1 -triple x86_64-pc-linux-gnu -fsyntax-only -verify -std=c++11 %s -fexperimental-new-constant-interpreter
   3
   4 static int test0 __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
   5 static void test1() __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
   6
   7 namespace test2 __attribute__((weak)) { // expected-warning {{'weak' attribute only applies to variables, functions, and classes}}
   8 }
   9
  10 namespace {
  11   int test3 __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
  12   void test4() __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
  13 }
  14
  15 struct Test5 {
  16   static void test5() __attribute__((weak)); // no error
  17 };
  18
  19 namespace {
  20   struct Test6 {
  21     static void test6() __attribute__((weak)); // expected-error {{weak declaration cannot have internal linkage}}
  22   };
  23 }
  24
  25 // GCC rejects the instantiation with the internal type, but some existing
  26 // code expects it. It is also not that different from giving hidden visibility
  27 // to parts of a template that have explicit default visibility, so we accept
  28 // this.
  29 template <class T> struct Test7 {
  30   void test7() __attribute__((weak)) {}
  31   static int var __attribute__((weak));
  32 };
  33 template <class T>
  34 int Test7<T>::var;
  35 namespace { class Internal {}; }
  36 template struct Test7<Internal>;
  37 template struct Test7<int>;
  38
  39 class __attribute__((weak)) Test8 {}; // OK
  40
  41 __attribute__((weak)) auto Test9 = Internal(); // expected-error {{weak declaration cannot have internal linkage}}
  42
  43 [[gnu::weak]] void weak_function();
  44 struct WithWeakMember {
  45   [[gnu::weak]] void weak_method();
  46   [[gnu::weak]] virtual void virtual_weak_method();
  47 };
  48 constexpr bool weak_function_is_non_null = &weak_function != nullptr; // expected-error {{must be initialized by a constant expression}}
  49 // expected-note@-1 {{comparison against address of weak declaration '&weak_function' can only be performed at runtime}}
  50 constexpr bool weak_method_is_non_null = &WithWeakMember::weak_method != nullptr; // expected-error {{must be initialized by a constant expression}}
  51 // expected-note@-1 {{comparison against pointer to weak member 'WithWeakMember::weak_method' can only be performed at runtime}}
  52 // GCC accepts this and says the result is always non-null. That's consistent
  53 // with the ABI rules for member pointers, but seems unprincipled, so we do not
  54 // follow it for now.
  55 // TODO: Consider warning on such comparisons, as they do not test whether the
  56 // virtual member function is present.
  57 constexpr bool virtual_weak_method_is_non_null = &WithWeakMember::virtual_weak_method != nullptr; // expected-error {{must be initialized by a constant expression}}
  58 // expected-note@-1 {{comparison against pointer to weak member 'WithWeakMember::virtual_weak_method' can only be performed at runtime}}
  59
  60 // Check that no warnings are emitted.
  61 extern "C" int g0;
  62 extern int g0 __attribute__((weak_import));
  63
  64 extern "C" int g1 = 0; // expected-note {{previous definition is here}}
  65 extern int g1 __attribute__((weak_import)); // expected-warning {{attribute declaration must precede definition}}