Why does C need "struct" keyword and not C++?

Question

I've always been a little confused about what's going on here:

#include <stdio.h>

int main() {  
    timeval tv;
    tv.tv_sec = 1;

    for (;;) {
        select(0, 0, 0, 0, &tv);
        printf("%s
", "Hello World!");
    }
}

Sorry if that doesn't compile, just wrote it as a quick example.

Code like this won't compile under gcc unless I add the keyword struct prior to the use of the struct timeval. g++ on the other hand handles it fine as is.

Is this a difference between how C and C++ handle structures or is it just a difference in the compilers? (I'm very C++ oriented, and the use of struct in C on lines like this has always somewhat baffled me).

Answer 1

Syntactically both treat struct almost the same. Only C++ has added an extra rule that allows to omit the struct (and class) keyword if there is no ambiguity.

If there is ambiguity, also C++ requires the struct keyword in some places. A notorious example is stat on POSIX systems where there is a struct stat and a function stat.