Programming Forums > Application Development > C++

Soulstorm · Jan 2nd, 2007, 4:17 AM

I have been experimenting with void pointers. I have encountered many problems, since I want to implement them into a very big project, but I made some examples that I believe that if I understand them, I will be able to use them efficiently.

Here is my first example:

 cpp Syntax (Toggle Plain Text) 
int main (int argc, char * const argv[]) {
	int *p;
	int a = 100;
	void *v;
	p = &a;
	v = p;
	std::cout << v;
	return 0;
}
int main (int argc, char * const argv[]) {
	int *p;
	int a = 100;
	void *v;
	p = &a;
	v = p;
	std::cout << v;
	return 0;
}

The result I am getting is '0xbffff9c0' from the cout function. Actually, I had predicted it, but I don't know how can I access the contents of the void pointer. Can you help?

Another example:

 cpp Syntax (Toggle Plain Text) 
void f(void *p){
	printf("%s",p);
}
 
int main (int argc, char * const argv[]) {
	char p[] = "hello!";
	f(p);
	return 0;
}
void f(void *p){
	printf("%s",p);
}

int main (int argc, char * const argv[]) {
	char p[] = "hello!";
	f(p);
	return 0;
}

The above code works as expected. It shows 'hello'. But if I replace the printf fuunction with the cout:

 cpp Syntax (Toggle Plain Text) 
void f(void *p){
	cout << p;
}
 
int main (int argc, char * const argv[]) {
	char p[] = "hello!";
	f(p);
	return 0;
}
void f(void *p){
	cout << p;
}

int main (int argc, char * const argv[]) {
	char p[] = "hello!";
	f(p);
	return 0;
}

I get an address! (0xbffff9b8).

Can you please explain to me why this is happenning (in both examples) and what can I do to dereference a void pointer so that I can access the elements it points to?

Jan 2nd, 2007, 4:17 AM	#1
Soulstorm Hobbyist Programmer Join Date: Jan 2006 Location: Menidi, Athens, Greece Posts: 243 Rep Power: 3	Void Pointers Question about dereferencing I have been experimenting with void pointers. I have encountered many problems, since I want to implement them into a very big project, but I made some examples that I believe that if I understand them, I will be able to use them efficiently. Here is my first example: cpp Syntax (Toggle Plain Text) int main (int argc, char * const argv[]) { int p; int a = 100; void v; p = &a; v = p; std::cout << v; return 0; } int main (int argc, char * const argv[]) { int p; int a = 100; void v; p = &a; v = p; std::cout << v; return 0; } The result I am getting is '0xbffff9c0' from the cout function. Actually, I had predicted it, but I don't know how can I access the contents of the void pointer. Can you help? Another example: cpp Syntax (Toggle Plain Text) void f(void p){ printf("%s",p); } int main (int argc, char const argv[]) { char p[] = "hello!"; f(p); return 0; } void f(void p){ printf("%s",p); } int main (int argc, char const argv[]) { char p[] = "hello!"; f(p); return 0; } The above code works as expected. It shows 'hello'. But if I replace the printf fuunction with the cout: cpp Syntax (Toggle Plain Text) void f(void p){ cout << p; } int main (int argc, char const argv[]) { char p[] = "hello!"; f(p); return 0; } void f(void p){ cout << p; } int main (int argc, char const argv[]) { char p[] = "hello!"; f(p); return 0; } I get an address! (0xbffff9b8). Can you please explain to me why this is happenning (in both examples) and what can I do to dereference a void pointer so that I can access the elements it points to? __________________ Project::Soulstorm (personal homepage)

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Programming Forums > Application Development > C++

Void Pointers Question about dereferencing