c++ - 为什么不能将字符串文字连接到 __FUNCTION__？

Question

__FUNCTION__ 不是字符串文字吗？我一直认为它是 - 沿着 __FILE__ 的路线，但我刚刚发现我不能将字符串文字相邻地连接到它。如果它不是字符串文字，它被定义为什么？我无法让 cscope 解决它。

例如

#include <iostream>

int main( int argc, char* argv[] )
{
  std::cout << __FILE__ << std::endl;
  std::cout << __FILE__ "A" << std::endl;
  std::cout << __FUNCTION__ << std::endl;
  //std::cout << __FUNCTION__ "A" << std::endl; // Doesn't compile.
  return 0;
}

包含问题行时的错误:

>g++ --version
g++ (GCC) 4.8.3 20140911 (Red Hat 4.8.3-7)
Copyright (C) 2013 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

>g++ -g main.cpp 
main.cpp: In function 'int main(int, char**)':
main.cpp:8:29: error: expected ';' before string constant
   std::cout << __FUNCTION__ "A" << std::endl; // Doesn't compile.

Answer 1

Isn't __FUNCTION__ a string literal?

没有。

来自 https://gcc.gnu.org/onlinedocs/gcc-7.2.0/gcc/Function-Names.html

These identifiers are variables, not preprocessor macros, and may not be used to initialize char arrays or be concatenated with string literals.