Hi,
Saurabh Sehgal wrote:
Hi all,
Thanks for the reply !
I was able to write this function successfully.
This would lead me to my next question.
Is there anyway to test if a memory address is valid or not without causing a
segmentation fault and catching this maybe in a signal handler ?
Is there a safe way in the same function " void * foo (char * addr)"
to check that
if the address contained in the string represented by "char * addr" is valid
before returning it.
static inline int is_invalid_addr( const void *p )
{
int dev_null_fd = open("/dev/null", O_RDWR);
if(dev_null_fd < 0)
return -1;
/* HACK: on some systems we can not write to check for pointer
validity */
size_t ret = fcntl( dev_null_fd, F_GETLK, p );
ret = ( errno == EFAULT );
errno = 0;
return ret;
}
You can use this function to check whether given address is accessible.
-- Rahul Patel.
Thank you !
Saurabh
On Sun, Jul 26, 2009 at 4:14 AM, Eric Polino<aluink@xxxxxxxxx> wrote:
sure, you can just write a function that declares a void * and uses it as a
regular numeric type such as int or whatnot and parses the string
representation as a numeric value into that variable. You can do stuff the
same as you would with any other integer type, "x += 10; x -= 18;". So the
function would look something like
void *foo(const char *addr){
void *parsed_value = 0;
....
/* Parse addr into parsed_value */
....
/* parsed_value == value_described_by(addr) */
return parsed_value;
}
Parsing addr into parsed_value is left as an exercise to the reader ;)
"None are more hopelessly enslaved than those who falsely believe they are
free."
--Goethe
"Freedom is living without government coercion."
--Ron Paul (www.ronpaul2008.com)
On Sun, Jul 26, 2009 at 03:39, Saurabh Sehgal <saurabh.r.s@xxxxxxxxx> wrote:
Hi all,
I had a quick question:
Let's say I design a function with the signature:
void * foo( char * addr ) ; ,
where addr is a string that represents a valid memory address ...
so the way someone can call this function is ...
char * addr = "0xae456778" // assume this is a valid memory address on
the machine
foo( addr ) ;
Is it possible to take this address in string form, and assign it to
an actual pointer of void * type ?
I want the function "foo" to return a pointer pointing to the memory
location as indicated
by the string passed in.
Thank you !
Saurabh
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