运行这个:
#define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__)
template< int PathLength >
constexpr const int startfindlastslash(const char (&path)[PathLength]) {
return PathLength;
}
int main(int argc, char const *argv[])
{
STATIC_ASSERT( startfindlastslash( "cppdebugger/test_debugger.cpp" ) == 11 );
}
你得到了:
g++ -o main.exe --std=c++14 test_debugger.cpp
test_debugger.cpp: In function ‘int main(int, const char**)’: test_debugger.cpp:1:28: error: static assertion failed: startfindlastslash( "cppdebugger/test_debugger.cpp" ) == 11 #define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__) ^ test_debugger.cpp:10:5: note: in expansion of macro ‘STATIC_ASSERT’ STATIC_ASSERT( startfindlastslash( "cppdebugger/test_debugger.cpp" ) == 11 ); ^~~~~~~~~~~~~
clang++ -Xclang -ast-print -fsyntax-only --std=c++14 test_debugger.cpp > main.exe
test_debugger.cpp:10:5: error: static_assert failed due to requirement 'startfindlastslash("cppdebugger/test_debugger.cpp") == 11' "startfindlastslash( \"cppdebugger/test_debugger.cpp\" ) == 11" STATIC_ASSERT( startfindlastslash( "cppdebugger/test_debugger.cpp" ) == 11 ); ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ test_debugger.cpp:1:28: note: expanded from macro 'STATIC_ASSERT' #define STATIC_ASSERT(...) static_assert(__VA_ARGS__, #__VA_ARGS__) ^ ~~~~~~~~~~~ 1 error generated.
编译器不会告诉它应该获得哪个值,它只是说该值不相等。
最佳答案
我经常发现包裹 static_asserts
很有用。在函数模板中。然后编译器至少会打印错误消息中的函数模板参数。如果您将此策略与@Phil1970 的值(value)模板方法结合起来,您会得到相当不错的结果。
使用 GCC 编译时,以下代码片段会打印包含您的值的错误消息: In instantiation of 'constexpr void assert_equal(const_val<T, A>, const_val<U, B>) [with T = int; T A = 30; U = int; U B = 11]'
Clang 更好:<source>:13:5: error: static_assert failed due to requirement '30 == 11' "Values are not equal!"
.
#define MAKE_CONST(x) const_val<decltype(x), x>{}
#define STATIC_ASSERT_EQUAL(x, y) assert_equal(MAKE_CONST(x), MAKE_CONST(y));
template<typename T, T val>
struct const_val {
constexpr const_val() = default;
constexpr const_val(T v) {}
};
template<typename T, T A, typename U, U B>
constexpr void assert_equal(const_val<T, A>, const_val<U, B>) {
static_assert(A == B, "Values are not equal!");
}
template< int PathLength >
constexpr const int startfindlastslash(const char (&path)[PathLength]) {
return PathLength;
}
int main(int argc, char const *argv[])
{
STATIC_ASSERT_EQUAL(startfindlastslash( "cppdebugger/test_debugger.cpp" ), 11);
}
这并不完全是您使用的语法,为了方便起见,它涉及一个额外的宏,但希望它足以满足您的目的...
实时代码 here .
关于c++ - 如何让 `static_assert` 打印失败时得到的值?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/59473672/