添加要断言的消息

你在这儿运气不好。最好的方法是定义你自己的 assert

#ifndef NDEBUG
#   define ASSERT(condition, message) \
    do { \
        if (! (condition)) { \
            std::cerr << "Assertion `" #condition "` failed in " << __FILE__ \
                      << " line " << __LINE__ << ": " << message << std::endl; \
            std::terminate(); \
        } \
    } while (false)
#else
#   define ASSERT(condition, message) do { } while (false)
#endif

这将定义 ASSERT 仅当没有调试宏 NDEBUG 未定义。

然后你可以这样使用它:

ASSERT((0 < x) && (x < 10), "x was " << x);

这比你的用法简单一点,因为你不需要字符串化 "x was " 和 x

在不编写自己的例程的情况下包含消息有一些老技巧:

首先是:

bool testbool = false;
assert(("this is the time", testbool));

还有:

bool testbool = false;
assert(testbool && "This is a message");

第二个有效,因为字符串的值将是非零的。

一个更好的替代方法是教导调试器在assert失败时停止,然后您不仅可以检查x值,还可以检查包括调用堆栈在内的任何其他信息。也许,这才是你真正想要的。 这里提到了示例实现 Ways to show your co-programmers that some methods are not yet implemented in a class when programming in C++

#define ASSERT_WITH_MESSAGE(condition, message) do { \
if (!(condition)) { printf((message)); } \
assert ((condition)); } while(false)

#include <pempek_assert.h>

int main()
{
  float min = 0.0f;
  float max = 1.0f;
  float v = 2.0f;
  PEMPEK_ASSERT(v > min && v < max,
                "invalid value: %f, must be between %f and %f", v, min, max);

  return 0;
}

将提示您:

Assertion 'v > min && v < max' failed (DEBUG)
  in file e.cpp, line 8
  function: int main()
  with message: invalid value: 2.000000, must be between 0.000000 and 1.000000

Press (I)gnore / Ignore (F)orever / Ignore (A)ll / (D)ebug / A(b)ort:

在哪里?

• (一) 忽略当前断言
• 在程序的剩余执行中忽略它
• Ignore(A)ll:忽略所有剩余断言(所有文件和行)
• (D) ebug:如果附加了调试器,则进入调试器,否则 abort() (在窗户上, 系统将提示用户附加调试器)
• 中止() 立即

您可以在那里了解更多信息:

• blog post
• GitHub project

延续康德拉德·鲁道夫的回答:

#include <iostream>

#ifdef NDEBUG
#define assert(condition, message) 0
#else
#define assert(condition, message)\
   (!(condition)) ?\
      (std::cerr << "Assertion failed: (" << #condition << "), "\
      << "function " << __FUNCTION__\
      << ", file " << __FILE__\
      << ", line " << __LINE__ << "."\
      << std::endl << message << std::endl, abort(), 0) : 1
#endif

void foo() {
   int sum = 0;
   assert((sum = 1 + 1) == 3, "got sum of " << sum << ", but expected 3");
}

int main () {
   foo();
}

Assertion failed: ((sum = 1 + 1) == 3), function foo, file foo.cpp, line 13.
got sum of 2, but expected 3
zsh: abort      ./a.out

这类似于std::assert宏在我的系统上输出的内容,只是附加了一条用户定义的消息

是的,这是可能的。

启用表达式 better_assert((0 < x) && (x < 10), std::string("x was ") + myToString(x));

#define better_assert(EXPRESSION, ... ) ((EXPRESSION) ? \
(void)0 : print_assertion(std::cerr, \
"Assertion failure: ", #EXPRESSION, " in File: ", __FILE__, \ 
" in Line: ", __LINE__ __VA_OPT__(,) __VA_ARGS__))

在哪儿 print_assertion 是执行断言的代理函数。当 EXPRESSION 已评估 false ,所有调试信息 __VA_ARGS__ std::cerr . 此函数接受任意数量的参数,因此我们应该实现可变模板函数:

template< typename... Args >
void print_assertion(std::ostream& out, Args&&... args)
{
    out.precision( 20 );
    if constexpr( debug_mode )
    {
        (out << ... << args) << std::endl;
        abort();
    }
}

(out << ... << args) << std::endl; 利用C++ 17中的折叠表达式 https://en.cppreference.com/w/cpp/language/fold );常量表达式 debug_mode

#ifdef NDEBUG
    constexpr std::uint_least64_t debug_mode = 0;
#else
    constexpr std::uint_least64_t debug_mode = 1;
#endif

值得一提的是 if constexpr( debug_mode ) 使用constexpr if( https://en.cppreference.com/w/cpp/language/if )自C++ 17导入。

总而言之,我们有:

#ifdef NDEBUG
    constexpr std::uint_least64_t debug_mode = 0;
#else
    constexpr std::uint_least64_t debug_mode = 1;
#endif

template< typename... Args >
void print_assertion(std::ostream& out, Args&&... args)
{
    out.precision( 20 );
    if constexpr( debug_mode )
    {
        (out << ... << args) << std::endl;
        abort();
    }
}
#ifdef better_assert
#undef better_assert
#endif
#define better_assert(EXPRESSION, ... ) ((EXPRESSION) ? (void)0 : print_assertion(std::cerr, "Assertion failure: ",  #EXPRESSION, " in File: ", __FILE__, " in Line: ",  __LINE__ __VA_OPT__(,) __VA_ARGS__))

double const a = 3.14159265358979;
double const b = 2.0 * std::asin( 1.0 );
better_assert( a==b, " a is supposed to be equal to b, but now a = ", a, " and b = ", b );

这将产生如下错误消息:

Assertion failure: a==b in File: test.cc in Line: 9 a is supposed to be equal to b, but now a = 3.1415926535897900074 and b = 3.141592653589793116
[1]    8414 abort (core dumped)  ./test

完整的源代码可在本报告中获得: https://github.com/fengwang/better_assert

按照康拉德·鲁道夫的回答,你可以做得更简洁一点

#include <assert.h>
#include <stdio.h>
#define ASSERT(condition,...) assert( \
    condition|| \
    (fprintf(stderr,__VA_ARGS__)&&fprintf(stderr," at %s:%d\n",__FILE__,__LINE__)) \
);

它在C语言中也起作用,