Initializing character arrays with memset

[MarkB]

Hi,

I have just realized that I was passing a pointer to pointer to memset function to initialize a character array but everything still seems to be working. Here is the "problematic" code:

char myArray[25];
memset(&myArray, 0, 25);
Notice the & operator in front of myArray in memset call. It should not work but it does????

The code should be without the & operator in front of myArray variable:
char myArray[25];
memset(myArray, 0, 25);

Does anybody know why the initial code is working with the unnecessary & operator?
Thank you in advance.

Mark

[Sebastiani]

It's just a fluke. The label myArray resolves to a pointer to some data on the stack, but since a pointer wasn't actually declared, the address of the label must also resolve to the same address (although I'm not sure if this is guaranteed by the standard). Had this been a pointer to the array, it would have been a different story, eg:

int main( void )
{
	char 
		buf[ 256 ], 
		* ptr = buf;
	printf( "Value of 'buf': 0x%x\n", buf );
	printf( "Address of 'buf' 0x%x\n", &buf );
	printf( "Value of 'ptr': 0x%x\n", ptr );
	printf( "Address of 'ptr' 0x%x\n", &ptr );
	return 0;
}

So in short, you got lucky.

[cpjust]

If you're just initializing the whole array to 0, then here's an easier way:

char myArray[25] = {0};

[MarkB]

Hi,

I have just realized that I was passing a pointer to pointer to memset function to initialize a character array but everything still seems to be working. Here is the "problematic" code:

char myArray[25];
memset(&myArray, 0, 25);
Notice the & operator in front of myArray in memset call. It should not work but it does????

The code should be without the & operator in front of myArray variable:
char myArray[25];
memset(myArray, 0, 25);

Does anybody know why the initial code is working with the unnecessary & operator?
Thank you in advance.

Mark

[Sebastiani]

I'm not sure why you reposted this. You should post further comments here.

[cas]

The address of an array and the address of its first element (which is what you get when you leave off the &) are the same place, although different types. There's nothing inherently wrong with taking the address of an array, but it's usually not what you want. It works in this case because you don't care about the type (it's converted to void* either way).

[VirtualAce]

Threads merged.