Question

由于我工作的公司禁止使用boost，因此我需要在纯C ++中实现其功能。我已经研究了增强源，但它们似乎太复杂了，至少对我而言。我知道C ++ 0x standart中有一些名为static_assert()的东西，但我不想使用任何C ++ 0x功能。

Answer 1

另一个技巧（可以在C中使用）是在断言失败的情况下尝试构建负数大小的数组：

#define ASSERT(cond) int foo[(cond) ? 1 : -1]

作为奖励，您可以使用typedef而不是对象，以便它可以在更多上下文中使用，并且在成功时不会发生：

#define ASSERT(cond) typedef int foo[(cond) ? 1 : -1]

最后，建立一个名称冲突的可能性较小的名称（并且至少可以在不同的行中重用）：

#define CAT_(a, b) a ## b
#define CAT(a, b) CAT_(a, b)
#define ASSERT(cond) typedef int CAT(AsSeRt, __LINE__)[(cond) ? 1 : -1]

Answer 2

template<bool> struct StaticAssert;
template<> struct StaticAssert<true> {};

int main() {
   StaticAssert< (4>3) >(); //OK
   StaticAssert< (2+2==5) >(); //ERROR
}

Answer 3

这是我自己的代码库提取的静态断言实现：Pre-C++11 Static Assertions Without Boost。

用法：

STATIC_ASSERT(expression, message);

当静态断言测试失败时，会生成以某种方式包含STATIC_ASSERTION_FAILED_AT_LINE_xxx_message的编译器错误消息。

message必须是有效的C ++标识符，如no_you_cant_have_a_pony，它将产生包含以下内容的编译器错误：

STATIC_ASSERTION_FAILED_AT_LINE_1337_no_you_cant_have_a_pony：）

#define CONCATENATE(arg1, arg2)   CONCATENATE1(arg1, arg2)
#define CONCATENATE1(arg1, arg2)  CONCATENATE2(arg1, arg2)
#define CONCATENATE2(arg1, arg2)  arg1##arg2

/**
 * Usage:
 *
 * <code>STATIC_ASSERT(expression, message)</code>
 *
 * When the static assertion test fails, a compiler error message that somehow
 * contains the "STATIC_ASSERTION_FAILED_AT_LINE_xxx_message" is generated.
 *
 * /!\ message has to be a valid C++ identifier, that is to say it must not
 * contain space characters, cannot start with a digit, etc.
 *
 * STATIC_ASSERT(true, this_message_will_never_be_displayed);
 */

#define STATIC_ASSERT(expression, message)\
  struct CONCATENATE(__static_assertion_at_line_, __LINE__)\
  {\
    implementation::StaticAssertion<static_cast<bool>((expression))> CONCATENATE(CONCATENATE(CONCATENATE(STATIC_ASSERTION_FAILED_AT_LINE_, __LINE__), _), message);\
  };\
  typedef implementation::StaticAssertionTest<sizeof(CONCATENATE(__static_assertion_at_line_, __LINE__))> CONCATENATE(__static_assertion_test_at_line_, __LINE__)

  // note that we wrap the non existing type inside a struct to avoid warning
  // messages about unused variables when static assertions are used at function
  // scope
  // the use of sizeof makes sure the assertion error is not ignored by SFINAE

namespace implementation {

  template <bool>
  struct StaticAssertion;

  template <>
  struct StaticAssertion<true>
  {
  }; // StaticAssertion<true>

  template<int i>
  struct StaticAssertionTest
  {
  }; // StaticAssertionTest<int>

} // namespace implementation


STATIC_ASSERT(true, ok);
STATIC_ASSERT(false, ko);

int main()
{
  return 0;
}

Answer 4

您只需将宏从Boost source file复制到您自己的代码即可。如果您不需要支持Boost支持的所有编译器，您可以为编译器选择正确的定义，并省略该文件中的其余#ifdef。

Answer 5

我相信这应该有效：

template<bool> struct CompileTimeAssert;   
template<> struct CompileTimeAssert<true>{};
#define STATIC_ASSERT(e) (CompileTimeAssert <(e) != 0>())

Answer 6

我正在使用以下头文件，其中包含其他人的代码......

#ifndef STATIC_ASSERT__H
#define STATIC_ASSERT__H

/* ripped from http://www.pixelbeat.org/programming/gcc/static_assert.html */

#define ASSERT_CONCAT_(a, b) a##b
#define ASSERT_CONCAT(a, b) ASSERT_CONCAT_(a, b)
/* These can't be used after statements in c89. */
#ifdef __COUNTER__
  /* microsoft */
  #define STATIC_ASSERT(e) enum { ASSERT_CONCAT(static_assert_, __COUNTER__) = 1/(!!(e)) }
#else
  /* This can't be used twice on the same line so ensure if using in headers
   * that the headers are not included twice (by wrapping in #ifndef...#endif)
   * Note it doesn't cause an issue when used on same line of separate modules
   * compiled with gcc -combine -fwhole-program.  */
  #define STATIC_ASSERT(e) enum { ASSERT_CONCAT(assert_line_, __LINE__) = 1/(!!(e)) }
#endif

/* http://msdn.microsoft.com/en-us/library/ms679289(VS.85).aspx */
#ifndef C_ASSERT
#define C_ASSERT(e) STATIC_ASSERT(e)
#endif

#endif

没有提升的BOOST_STATIC_ASSERT

6 个答案: