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Ovid (2709)
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Stuff with the Perl Foundation. A couple of patches in the Perl core. A few CPAN modules. That about sums it up.
Ungrokking C
I was doing a bit of C programming when I got stumped:
#include <math.h>
#include <stdio.h>
int main(void) {
double x = 10.0, y = 3.0;
printf("%f\n", pow(x, y));
return (0);
}
I couldn't compile that with gcc because I kept getting an undefined reference to 'pow' error. I tried explicitily declaring the function signature before main(), but that also failed. A bit of research revealed that gcc requires I explicitly link the math library when I compile a program (by passing -lm as an argument.)
That seems odd. If I explicitly link the math library, why do I need an #include <math.h> statement in my program? It turns out that I don't.
#include <stdio.h>
double pow(double x, double y);
int main(void) {
double x = 10.0, y = 3.0;
printf("%f\n", pow(x, y));
return (0);
}
I can then compile that code with
gcc -Wall testpow.c -o testpow -lm
The above code worked fine, but it seems to me that a program should contain all of the necessary elements to get it to run. Having to push some of this out to the compiler seems wrong. I suspect that I've been programming Perl for so long that working with other languages is simply a foreign experience now. This is Not Good.
Update: I discovered, after a bit of research, that many people are complaining about this. What appear to be standard C programs typed directly from book examples are mysteriously failing. Since I am using gcc 3.2, a relatively recent compiler, I'm totally confused as to the thought process here. C, while being relatively simple, still has a higher barrier to entry than many other languages. Designing a compiler that further raises this barrier seems foolish.
I pour myself a cup of strong coffee. :-)
-- Jarkko Hietaniemi
It's actually not that bad (Score:4, Informative)
That's right - the
powfunction is not provided by the C language. If you need to use functionality provided by the language, you have to add in libraries. Just like in Perl.As it should; a function prototype doesn't actually contain any code to implement a function, it just allows you to use that function in your code without the compiler screaming. Just like in Perl.
Only when you're using functions provided by the math library; when you're not using functions from a given library, you don't need to link in that library. Just like in Perl.
All the
#include <math.h>does is give you a handy collection of prototypes; it doesn't provide any code. Since you've provided your own prototype, you don't need it.Well, no. You can try to use stuff from a library, but if you don't make that library available, your code isn't going to work. Just like in Perl.
Well, as I've mentioned, this is all just like Perl...
Well, there are a lot of books about the language which are badly written. Just like Perl...
Reply to This
Re:It's actually not that bad (Score:2)
Thank you very much! That does clear things up. My C, as should be readily apparent, is terribly rusty.
The compilation isn't failing; it's the linking (Score:1)
gcc -c -o test.o test.c
You'll end up with a compiled object file 'test.o' from your source file 'test.c'.
Then, the following linking command will fail without the -lm:
gcc -lm -o test test.o