是否存在相當於'static_assert”的靜態警告，它會產生警告而不是停止編譯？

有靜態警告嗎？

這個問題旨在確定是否存在一種機制來實現類似於 static_assert 的靜態警告，但它不會停止編譯，而是觸發編譯期間的警告訊息。

實現

利用Michael E 的評論提供的見解，建議以下實現：

<code class="c++">#if defined(__GNUC__)
#define DEPRECATE(foo, msg) foo __attribute__((deprecated(msg)))
#elif defined(_MSC_VER)
#define DEPRECATE(foo, msg) __declspec(deprecated(msg)) foo
#else
#error This compiler is not supported
#endif

#define PP_CAT(x,y) PP_CAT1(x,y)
#define PP_CAT1(x,y) x##y

namespace detail
{
    struct true_type {};
    struct false_type {};
    template <int test> struct converter : public true_type {};
    template  struct converter : public false_type {};
}

#define STATIC_WARNING(cond, msg) \
struct PP_CAT(static_warning,__LINE__) { \
  DEPRECATE(void _(::detail::false_type const& ),msg) {}; \
  void _(::detail::true_type const& ) {}; \
  PP_CAT(static_warning,__LINE__)() {_(::detail::converter());} \
}

// Note: using STATIC_WARNING_TEMPLATE changes the meaning of a program in a small way.
// It introduces a member/variable declaration.  This means at least one byte of space
// in each structure/class instantiation.  STATIC_WARNING should be preferred in any 
// non-template situation.
//  'token' must be a program-wide unique identifier.
#define STATIC_WARNING_TEMPLATE(token, cond, msg) \
    STATIC_WARNING(cond, msg) PP_CAT(PP_CAT(_localvar_, token),__LINE__)</int></code>

調用

宏可以在多個範圍內調用，包括命名空間、結構和函數。以下是範例：

<code class="c++">#line 1
STATIC_WARNING(1==2, "Failed with 1 and 2");
STATIC_WARNING(1 struct wrap
{
  typedef T type;
  STATIC_WARNING(4==5, "Bad with 4 and 5");
  STATIC_WARNING(4;</code>

編譯結果

啟用適當的編譯器警告後，提供的實作會在編譯時產生警告訊息，傳達指定的訊息：

GCC 4.6：

static_warning1::_: Failed with 1 and 2
Foo::static_warning6::_: 2 and 3: oops
func()::static_warning12::_: Not so good on 3 and 4
wrap<t>::static_warning19::_: Bad with 4 and 5</t>

Visual C 2010：

'static_warning1::_': Failed with 1 and 2
'Foo::static_warning6::_': 2 and 3: oops
'func::static_warning12::_': Not so good on 3 and 4
'wrap<t>::static_warning19::_': Bad with 4 and 5</t>

Clang 3.1：

'_' is deprecated: Failed with 1 and 2
'_' is deprecated: 2 and 3: oops
'_' is deprecated: Not so good on 3 and 4
'_' is deprecated: Bad with 4 and 5

Clang 3.1：

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