C++程序中出现 fatal error C1189: #error : eh.h is only for C++!

fatal error C1189: #error : "eh.h is only for C++!"

#ifndef __cplusplus
#error "eh.h is only for C++!"
#endif

The cause :
include a C++ header file in a .c file.
for example: In a.c, you included <iostream>