Visual Studio是否在打印函数地址时出现错误？ [英] Is Visual Studio buggy in printing the function address?

问题描述

采取以下测试用例：

#include <iostream>

void foo()
{}

int main()
{
   std::cout << &foo << std::endl;
}

GCC 4.1.2，GCC 4.8和GCC 4.9 C ++ 11）在构建并编译时，所有提供以下输出：

GCC 4.1.2, GCC 4.8 and GCC 4.9 (C++03 and C++11) all give the following output when building and then compiling:

$ g++ main.cpp -o test && ./test
main.cpp: In function 'int main()':
main.cpp:8:23: warning: the address of 'void foo()' will always evaluate as 'true' [-Waddress]
   std::cout << &foo << std::endl;
                 ^
1

这可能是因为函数指针转换为 bool （并且转换为 void *

This is supposedly because the only viable stream insertion for the function pointer is conversion-to-bool (and a cast to void* would be required to actually get an address into the stream).

但是，Microsoft Visual Studio 2012和2013会输出指针地址。

However, Microsoft Visual Studio 2012 and 2013 output a pointer address instead.

的工具链是否符合？

推荐答案

MSVC可以使函数正确运行，并执行从函数指针到 bool 如果禁用语言扩展（ / Za 切换）。如果你这样做，你的代码产生以下警告（VS2013上 / W4 ）

MSVC can be made to function correctly and perform the conversion from function pointer to bool if you disable language extensions (/Za switch). If you do that, your code produces the following warnings (at /W4 on VS2013)

1>main.cpp(8): warning C4305: 'argument' : truncation from 'void (*)(void)' to 'std::_Bool'
1>main.cpp(8): warning C4800: 'void (*)(void)' : forcing value to bool 'true' or 'false' (performance warning)

，输出为 1

此行为是在 部分 p>

This behavior is documented under the Casts section

C ++编译器和C编译器都支持这些非ANSI类型转换：

...

非ANSI转换的数据指针的函数指针

Both the C++ compiler and C compiler support these kinds of non-ANSI casts:
...
Non-ANSI casts of a function pointer to a data pointer

没错，下面的行只编译 / Za disabled

Sure enough, the following line compiles only with /Za disabled

void *p = &foo;

禁用语言扩展会生成错误消息

Disabling language extensions produces the error message

1>main.cpp(8): error C2440: 'initializing' : cannot convert from 'void (*)(void)' to 'void *'
1>          There is no context in which this conversion is possible

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