RPGDX > Forums > Off Topic > C Questions

Jihgfed Pumpkinhead · Posted: Fri Jul 04, 2003 1:44 pm Post subject: C Questions

Well, I've been messing around in C for a while now, and I have some non-googlable (or at least, very difficult to google (I just love using google as a verb)) questions, and I'd be grateful to anyone who could shed some light on them.

1. Looking at source, I've noticed two very different approaches to choosing variable types. Some people just use ints for regular numbers, floats for real numbers, and chars for characters, while others are careful about picking shorts, longs, doubles, w_chars, what-have-you. I've heard that ints are faster (while the others are obviously more space-efficient), but is does it make enough a difference either way that I should worry about optimizing?

2. Why are functions like "exit ()", "abort ()", and those <stdarg> functions in the library, instead of in the language itself? Would it actually be possible for me to duplicate these functions myself (if, that is, I knew what I was doing)?

3. Where are NULL, EXIT_SUCCESS, and EXIT_FAILURE defined? I seem to get them whenever I include any standard library header, so it's not a priority, but I would like to know where they're actually kept in case I ever need to change the value of NULL (yes, that's a joke).

4. I have only the vaguest idea of what a "profiler" is; where can I learn more?

Rainer Deyke · Demon Hunter Joined: 05 Jun 2002 Posts: 672

valderman · Posted: Fri Jul 04, 2003 4:58 pm Post subject:

1: When porting code, ints are generally faster, since the compiler can make them whatever size the target CPU likes best.

4. A profiler is (if I got this right) a program which checks which parts of your code needs optimizing (takes the longest time to run).
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BigManJones · Scholar Joined: 22 Mar 2003 Posts: 196

Jihgfed Pumpkinhead · Posted: Sun Jul 06, 2003 9:18 am Post subject: Satiation of Curiosity

Thanks, everybody, for sating my curiousity... well, almost.

Rainer, why is exit () bad style? I use it whenever I bump into a fatal error. Should I not be?

Rainer Deyke · Demon Hunter Joined: 05 Jun 2002 Posts: 672

There are two problems with 'exit':

1. You still have to perform clean-up. You can do it manually before calling 'exit', or you can use 'atexit', but both options are somewhat messy and error-prone.

2. There's no way to "catch" an 'exit'. If you later decide that you just want to return to the main menu instead of exiting the program entirely, you'll have to rewrite a lot of code.

In C++, exceptions are definitely better than 'exit'. In C, the situation is less obvious, but I'd still avoid 'exit' where possible.

DrunkenCoder · Demon Hunter Joined: 29 May 2002 Posts: 559

In C you don't have exceptions, use setjmp and longjmp instead.
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Rainer Deyke · Demon Hunter Joined: 05 Jun 2002 Posts: 672

'setjmp' and 'longjmp' don't really help with clean-up. I like those functions even less than I like 'exit'. If I was still working in C, I would probably just use special return values to indicate error conditions. Then again, there is very little that could convince me to use C at this point.

DrunkenCoder · Demon Hunter Joined: 29 May 2002 Posts: 559

err, actually they do help but it requires you to think a bit, a habit not to many coders seems to have... of coures by themself they don't do anything to actually help you, but if you couple them with carfully checking your returnvalues they can be a great help
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twinsen · Posted: Mon Jul 07, 2003 10:56 pm Post subject:

Whether it be goto, exit, end, stop or whatever other BASIC function everyones talking about. I've written hundreds of C/C++ apps/games since I started programming, from boring business applications to 3D games. All I can say is I've never needed- nor missed one of these functions. If you structure your code correctly you should never need them. My two cents.
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Jihgfed Pumpkinhead · Posted: Thu Jul 10, 2003 1:52 am Post subject: Error-Handling

The more I think about it, the more I can see the value in using return values to indicate error status. But if I start doing that consistently, what do I do with functions that need to really return a value? Via arguments? Is it worth the effort learning C++ exception handling? I've managed to get by without so far, but if it'll make my life easier in the long run I'm all for it.

Rainer Deyke · Demon Hunter Joined: 05 Jun 2002 Posts: 672

Jihgfed Pumpkinhead · Posted: Thu Jul 10, 2003 5:27 am Post subject: Yay, Exceptions. Thanks.

Thanks, Rainer, I'll set out to learn exceptions then. C++ is just so huge (well, compared to any language with which I'm familiar) that I set about learning about it piecemeal. Now that I'm ready and have a use for it, it's time for exceptions. Hmm, I can just picture it now. No more "loadBmpCrash", "loadBmpNoCrash" to determine what to do with in case of error. Yay!

And thanks everybody for all the help here. It's been nice learning a little more about the language.