implicit declaration of malloc

Hi, I am learning C and the book made me type in the included program. Its teh part about using malloc/free functions.

It compiles fine & works but my compiler gives me the following warnings:

1 - implicit declaration of malloc
2 - assignment makes pointer from integer

Above are both about the line which has malloc in it and the last warning is:

3: implict declaration of function free

What exactly is a implicit declaration ? I know malloc returns an adres to allocated memory but why is it implicit ?

The program :

#include <stdio.h>

int main()
{
int index, aant;
float *vec, som;

// invoer arraylengte
printf("Aantal:\n"); scanf("%d",&aant);

// geheugen reserveren
vec = malloc(aant * sizeof(float));
if (!vec)
{
printf("geen geheugen!");
return 1;
}

// gegevens invoeren
for(index = 0; index < aant; index++)
{
printf("floatgetal:\n");
scanf("%g",&vec[index]);
}

// som berekenen
for(index = 0, som = 0; index < aant; index++)
som = som + vec[index];

// resultaat weergeven
printf("som: %g\n",som);

// geheugen vrijgeven
free(vec);

return 0;
}

add this line at the top and you'll be sorted
#include <stdlib.h>

1. #include <stdlib.h>

2a. Don't cast malloc - see
http://www.eskimo.com/~scs/C-faq/q7.7.html

2b. Casting would have suppressed this warning
> 2 - assignment makes pointer from integer

Thanks vVv, I already tried a float cast but didnt use the *.

Unregistered, thank you too, it got rid of the implicit warnings, and now that I seen this, I also remembered the chapter about functions & I understand (its because of the mssing functionprototype right ?)

Still why is it compiling succesfull although I missed the include of stdlib.h ?

... stdlib.h include does it all ? why no cast ?
I do not understand the explanation on that url exactly Salem.
What is ment with a generic pointer ? Does this mean that certain functions return a generic pointer which can be appointed to whatever type of pointer ?

> Still why is it compiling succesfull although I missed the include of stdlib.h ?
It was giving you warnings - for all the compiler knows, malloc returns int, and all would be well. Except it doesn't, and you should know that such a warning is a bit more serious than that.

And yes, stdlib.h contains the function prototype for malloc.

Any compiler warning should really be fixed IMO

> What is ment with a generic pointer ?
void* is the generic pointer type (in C), and since malloc returns void*, you can assign the result of malloc to any pointer variable without any casting.

I see, thanks!