C. To segmentation fault or not to segmentation fault, that is the question.


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# 8  
I've seen similar things in lots of code ported to different architectures. Quite a few different gotchas where something you can ignore harmlessly on one system, explodes on another, because something you took for granted has changed.

If you forget to include stdlib.h and math.h, your code may still work in 32-bit. It will assume these undeclared functions take all-integers and fill in the blanks. On a 64-bit system, where pointers are twice as large, that assumption is catastrophically wrong and causes memory addresses to get mangled, causing a crash.

Also, some systems let you do this, but don't depend on it, because most don't:
Code:
char *stuff="abcdefg";
stuff[2]='Q';

This User Gave Thanks to Corona688 For This Post:
# 9  
Code that has problems like that is NOT working, despite your personal point of view. It is undefined behavior. So you understand: undefined behavior means the program is no longer following any rules. It went into lala land. It could limp forward until it hits an exit point, it could format all disks, it could contact the New Horizons spacecraft and order a pizza.

I would say the compiler implementers for the box's C compiler code decided to do some goof-proofing. The limp along option. They likely have a SIGSEGV signal trap? I do not know. If you have a truss equivalent on the box, you can find out if the segmentation fault has been blocked somehow.

I am not trying to be a grumpy old problem monger. But undefined behavior is never "working". Ask Don Cragun or Corona688.
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# 10  
Another way that looks nicer and should still work on older compilers:

Code:
int main(int argc, char *argv[])
{
    if (argc <= 3)
    {
        printf("ERROR!\n\n");
        printf("Not enough arguments!\n");
        exit(1);
    }

    /* Older compilers only let you put variables at the top of a code block. */
    /* But you can put code blocks wherever you want. */
    {
        int NUM_1 = strtod(argv[1], NULL);
        int NUM_2 = strtod(argv[3], NULL);
        CHARACTER = *argv[2];
        printf("\n%i, %i, %c\n\n", NUM_1, NUM_2, CHARACTER);
    }

    return(0);
}

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# 11  
Hi all...

All cleaned up and working in AMIGA mode too now.
Thanks C688 for the code snippet.

I honestly thought that setting the parameters globally would suffice but it turns out I am wrong.

Thanks all for your input.
This embarrassment I will never forget.
# 12  
Don't be embarassed! C is very different from most languages. It's a high-level language which writes pure assembly, with all the safety you get from pure assembly...
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The Open Group released the Single UNIX Specification Version 2 in 1987.
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