今天在测试socket式IPC时，发现一个问题，一个文件以.c为后缀下可以用gcc编译过，以.cpp为命令则不可以。后来发现C与C++在一些标准上是不一样的。经查，这里应该注意几个问题：
gcc认为.cpp文件是c++文件，并且当做C++程序来进行编译。
g++编译时也用gcc，链接时用g++的链接库。而gcc编译C++程序时候，默认用c的链接库，如果要指定c++的链接库，可以手动指定：gcc -lstdc++
C语言中在申明函数时：
int foo();//表示函数可以有多个参数
int foo(void);//表示函数没有参数
C++在申明函数时候，以上两种都表示没有参数。
因此，为了保持可移植性，建议C/C++程序在声明无参函数时，都用int foo(void)这种写法。
参考：http://david.tribble.com/text/cdiffs.htm#C99-func-vararg
“
Empty parameter lists
C distinguishes between a function declared with an empty parameter list and a function declared with a parameter list consisting of only void. The former is an unprototyped function taking an unspecified number of arguments, while the latter is a prototyped function taking no arguments.
// C code
extern int foo(); // Unspecified parameters
extern int bar(void); // No parameters
void baz()
{
foo(0); // Valid C, invalid C++
foo(1, 2); // Valid C, invalid C++
bar(); // Okay in both C and C++
bar(1); // Error in both C and C++
}
C++, on the other hand, makes no distinction between the two declarations and considers them both to mean a function taking no arguments.
// C++ code
extern int xyz();
extern int xyz(void); // Same as 'xyz()' in C++,
// Different and invalid in C
For code that is intended to be compiled as either C or C++, the best solution to this problem is to always declare functions taking no parameters with an explicit void prototype. For example:
// Compiles as both C and C++
int bosho(void)
{
...
}
Empty function prototypes are a deprecated feature in C99 (as they were in C89).
[C99: §6.7.5.3]
[C++98: §8.3.5, C.1.6.8.3.5]
”