Thread: 0x00 in C

Hi all,

Just had q query wrt to the string "0x00" used in memset of character arrays in C. Could anyone reply on this!!

Thanks,
Vandrea

I don't understand your question. You don't pass a string to memset. If you're talking about the integral constant 0x00, it's just the hex encoding of, well, 0.

yep u were right..i meant of the integral constant!

Consider the follg eg:

Code:

char abc_ca[3];
memset(abc_ca,0x00,size(abc_ca));

So after the above memset i would have following values in my string

Code:

abc[0]={'\0'} 
abc[1]={'\0'} 
abc[2]={'\0'}

where {'\0'} identifies the end of string...Just wanted to know if my understanding is right!

Yep. On a side note, though, just keep in mind that sizeof used in that way won't work on an array passed to a function or on a pointer to an array.

Well, for example:

Code:

int main( void )
{	
	char 
		buf[ 1024 ], 
		* ptr = buf;
	printf("sizeof( buf ): %d\n", sizeof( buf ) );
	printf("sizeof( ptr ): %d\n", sizeof( ptr ) );
	return 0;
}

And when you pass an array to a function, it resolves to a pointer, so the effect is the same as in the second print statement.

Well, for example:

Code:

Code:
int main( void )
{	
	char 
		buf[ 1024 ], 
		* ptr = buf;
	printf("sizeof( buf ): %d\n", sizeof( buf ) );
	printf("sizeof( ptr ): %d\n", sizeof( ptr ) );
	return 0;
}

And when you pass an array to a function, it resolves to a pointer, so the effect is the same as in the second print statement.

I understood ur example but still wondering as to y cant we use sizeof in the above memset since

Code:

sizeof(abc_ca)

wuld return 3 I guess..

>> I understood ur example but still wondering as to y cant we use sizeof in the above memset since

The point is simply that you can use it on 'buf' but not 'ptr'. And inside a function, you'd have the same problem:

Code:

void test( char buf[ 1024 ] )
{	
	printf("sizeof( buf ): %d\n", sizeof( buf ) );
}

Thanks Sebastiani...Now I get it!