Question

I was wondering why does the following code not throw an error during compilation? :

#include <stdio.h>
char * func (char *);

int main()
{
    func("TINFO");
    func("INFO");
}

char * func(char * str)
{
    if (str[0] == 'T')
    return str + 1;
}

You see there is a return path from the function that does not return a char *

Similar Java code throws a compile time error, though.

Compiler used:

gcc (Ubuntu 4.4.3-4ubuntu5) 4.4.3

Answer 1

According to C standard, 6.9.1.12, reaching an end of the function is undefined behavior only if the caller uses the returned value:

If the } that terminates a function is reached, and the value of the function call is used by the caller, the behavior is undefined.

That’s why the compiler must let this code compile.