Re: A simple query about memory mgmt

["Santosh Pradhan" <santosh.pradhan@xxxxxxxxx>]

Thank you all.

Regards,
Santosh

On Wed, Aug 13, 2008 at 12:36 PM, Rene Herman <rene.herman@xxxxxxxxxxxx> wrote:

On 13-08-08 08:40, Peter Teoh wrote:

Not to annoy you further, but this is actually a fairly important point:

But if it is written as such:

#define NAME "santosh"

int main()
{
   char *p_name = NAME;
   char *q_name = NAME;
   if (p_name == q_name)
        printf("Hello, World\n");
   return 0;
}

I would not consider it an optimization.   Because, the string NAME
are allocated off from the static heap area.   And by nature #define
tell the compiler to inline duplicate the following contents - eg,
codes/functions, but for constant pointer values it is not.

#define does not allocate anything nor does it tell the compiler anything. Anything starting with a # in C is not handled by the compiler, but by the C pre-processor (man cpp).

Now, since only fairly recently, GCC's C pre-processor and C compiler are in fact integrated into a single binary but the conceptual split is still very much in place. The C pre-processor should conceptually be viewed as a general textfile processing tool and no more.

If _any_ different output would result from this and your first one:

#define NAME "santosh"
#define NAME1 "santosh"

int main()
{
   char *p_name = NAME;
   char *q_name = NAME1;
   if (p_name == q_name)
        printf("Hello, World\n");
   return 0;
}

you'd have found a violent bug in the tool chain. Consequently, if you'd expect any such difference, you'd have found a violent bug in your thinking ;-)

Rene.