[Cryptography] The GOTO Squirrel! [was GOTO Considered Harmful]

Patrick Chkoreff patrick at rayservers.net
Mon Mar 3 15:01:10 EST 2014

> Both gcc and llvm have this warning turned off by default, at least
> for C.  In fact, neither of them have it as part of -Wall - you have
> to explicitly request it (-Wunreachable-code).  From the
> documentation:  "This option is not made part of -Wall because in a
> debugging version of a program there is often substantial code which
> checks correct functioning of the program and is, hopefully,
> unreachable because the program does work.  Another common use of
> unreachable code is to provide behavior which is selectable at
> compile-time."

Yes, and I did an experiment with Ian's "moo" program.  All of the
following compiled just fine, without warning:

$ gcc -Wunreachable-code moo.c
$ gcc -Wunreachable-code -Wall moo.c
$ gcc -Wunreachable-code -Wall --std=c99 moo.c
$ gcc -Wunreachable-code -Wall --std=c99 --pedantic moo.c
$ gcc -Wunreachable-code -Wall --std=c99 --pedantic -ansi moo.c
$ gcc -Wunreachable-code -Wall --pedantic -ansi moo.c

I'm not even sure how to make the unreachable-code option do *anything* yet!

-- Patrick

P.S. Source code, courtesy Ian Grigg, no warranty express or implied:

#include <stdio.h>

int main(int argv, char **p)
    printf("hello world\n");
    goto happy;
    printf("hello black hole\n");

    return 0;

Compiler version:

$ gcc --version
gcc (Ubuntu/Linaro 4.8.1-10ubuntu9) 4.8.1

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