Thread: doesn't print what it's supposed to

That code prints exactly what it is required to. It is your understanding that is flawed if you expect them to be different.

The value 5 prints the same in octal (base 8), decimal (base 10), and hexadecimal (base 16) because it is less than 8. Try a larger value. A value of 8 will print as 10 in octal, and 8 in both hex and decimal. A value of 10 will print as 12 (octal), 10 (decimal), or A (hex).

> Process returned 23 <0x17> execution time : 1.031 s".
Plus you get some random number printed because you fall of the end of main without an explicit
return 0;
statement.

As an experiment. Note that online compilers are not compliant implementations although they use compliant compilers as their backends (this is just for fun)

Code:

#include <stdio.h>

#if defined(__clang__)
    static const char *cn = "clang";
#elif defined(__ICC) || defined(__INTEL_COMPILER)
    static const char *cn = "intel";
#elif defined(__GNUC__) || defined(__GNUG__)
    static const char *cn = "gcc";
#else
    static const char *cn = "unknown";
#endif
 
int main(void)
{
    printf("%s\n", cn);
#if defined(__GNUC__)
    printf("v %d.%d.%d\n", __GNUC__, __GNUC_MINOR__, __GNUC_PATCHLEVEL__);
    #ifdef __STRICT_ANSI__
        printf("Strict ANSI\n");
    #endif
#endif

    printf("File: %s\n", __FILE__);
}

for ideone, this does return a non-zero number and

Code:

gcc
v 4.8.1
prog.c

Codepad still not working, but from the about page:

Code:

 C: gcc 4.1.2 
flags: -O -fmessage-length=0 -fno-merge-constants -fstrict-aliasing -fstack-protector-all

Originally Posted by Hodor

Section (5.1.2.2.3) (c99, c11). C89 doesn't seem to say the same thing, but I only glanced at it.

C89 doesn't. In C89 (and in earlier versions of C predating that standard) the result of falling off the end of a function that returns a value is undefined.

C++ made main() special, so falling off the end was equivalent to a "return 0". This was adopted in C99.


This is actually one small area where fair number of C (post C89) and C++ compilers are technically non-compliant. If warning levels are turned up, a fair few compilers do warn about non-void functions (including main()) falling off the end though.