function declaration....

[roaan]

Normally when i use a function i make a declaration like this

void func();

So i am not passing any arguments to the function. But in some of the tutorials i noticed on the forum have the declaration like this

void func(void);

So till now i never used the void in my function declaration parentheses. But i was interested in knowing what does the compiler do when it comes across the above declaration in which i dont say void. Does it pass some garbage random values or the standard specifies that if a declaration doesnt specify anything it has to be assumed as void.

[tabstop]

The function declaration

void func();

means that the function func returns nothing and takes somewhere between zero and infinity parameters, all of type int. (EDIT: Not all of type int -- they can be of any type.) The function declaration

void func(void);

means that the function func returns nothing and accepts no parameters.

[MK27]

So to elaborate, using (void) is a safety check -- it means if you try and call the function with arguments, the compiler will catch your mistake.

Of course, it doesn't matter that much, since those arguments will be ignored anyway -- with () there is no way to access them. But if you were putting a library together, using (void) is probably a friendly thing to do.

[tabstop]

I guess I should be more specific. If the prototype is

void func();

then the actual function itself could be

void func(int x) {}

or

void func(double x) {}

or

void func(int x, double y, char *z, struct tm a, int b, int c, float q) {}

or even

void func() {}

In this last case, where an empty set of parentheses is used when defining the function proper, then it means that there are no arguments to the function.

[roaan]

But if i use this

[insert]

#include <stdio.h>
#include <stdlib.h>

int func();

int main(void)
{

	int i;
	i = func(2, 4, 2.0);

	printf("\n Func returned %d", i);

	return 0;
}

int func()
{
	
	return 1;
}

The compiler should throw an error but it doesnt.

[MK27]

The compiler should throw an error but it doesnt.

No, it will throw an error if

int func(void)

I guess I should be more specific. If the prototype is

void func();

then the actual function itself could be

Okay, that is how I do all my prototypes from now on then

[roaan]

No, it will throw an error if

int func(void)

Okay, that is how I do all my prototypes from now on then

No it simply generates a warning and runs even then

[insert]

#include <stdio.h>
#include <stdlib.h>

int func(void);

int main(void)
{

	int i;
	i = func(2, 4, 2.0);

	printf("\n Func returned %d", i);

	return 0;
}

int func()
{
	
	return 1;
}

[MK27]

No it simply generates a warning and runs even then

Not if you put (void) in the definition.

[BEN10]

@roann
This thread will be useful.