something about inet_ntoa()

I write a server using the function `char* inet_ntoa(struct in_addr in),` When I included the header
`<sys/socket.h>` and `<netinet/in.h>` ,an executable binary can be generated with compiler warnings, but a segment fault happens, when the program handle the return string from `inet_ntoa`. But when I added the header `<arpa/inet.h>,` everything seems ok.

What's the matter?

`arpa/inet.h` contains the declaration of `char* inet_ntoa(struct in_addr in)`. If you don't include this header your compiler will use implicit declaration `int inet_ntoa()`. Wrong declaration can easily lead to segfault, especially if you are on system where `sizeof(int)!=sizeof(void*)`.

If you are using `gcc` you can add `-Wall` flag. `gcc` will warn you about using functions without explicit declaration.