constants in C/C++ Post: 26695

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Top Forums Programming constants in C/C++ Post 26695 by Shobhit on Thursday 22nd of August 2002 09:23:50 AM

08-22-2002

Registered User

constants in C/C++

Hi all
My question is related to following sample code which tries to change consant value by pointers.(I know it is wrong practice but i am surprised by mis-behaviour)
The code:

#include <stdio.h>

int main()
{
const int x = 10;
int *y;
const int * const z = &x;

y = (int *)&x;
*y=11;
printf('%p %d ', y, *y);
printf('%p %d ', &x, x);
printf('%p %d ', z, *z);
return 0;
}

The output:

0012FF7C 11
0012FF7C 10
0012FF7C 11

The above output is when the program was compiled as cpp file and got
11
11
11
when compiled as "c" file.
Also
const int x=10;
int arr[x];
works with c++ compiler and not C.

My question is why is this mis-behaviour.

Shobhit

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LEARN ABOUT PHP

apc_define_constants

APC_DEFINE_CONSTANTS(3) 						 1						   APC_DEFINE_CONSTANTS(3)

apc_define_constants - Defines a set of constants for retrieval and mass-definition

SYNOPSIS

       bool apc_define_constants (string  $key, array  $constants, [bool  $case_sensitive = true])

DESCRIPTION

       define(3) is notoriously slow. Since the main benefit of APC is to increase the performance of scripts/applications, this mechanism is pro-
       vided to streamline the process of mass constant definition. However, this function does not perform as well as anticipated.

	For a better-performing solution, try the hidef extension from PECL.

       Note

	       To remove a set of stored constants (without clearing the entire cache), an empty array may be passed as the $constants	parameter,
	      effectively clearing the stored value(s).

PARAMETERS

	      o $key
		-  The	$key  serves  as  the  name  of  the  constant	set  being  stored.  This $key is used to retrieve the stored constants in
		apc_load_constants(3).

	      o $constants
		- An associative array of constant_name => value pairs. The constant_name must follow the normal  constant  naming  rules.   value
		must evaluate to a scalar value.

	      o $case_sensitive
		- The default behaviour for constants is to be declared case-sensitive; i.e.  CONSTANT and Constant represent different values. If
		this parameter evaluates to FALSE the constants will be declared as case-insensitive symbols.

RETURN VALUES

	Returns TRUE on success or FALSE on failure.

EXAMPLES

       Example #1

	      apc_define_constants(3) example

	      <?php
	      $constants = array(
		  'ONE'   => 1,
		  'TWO'   => 2,
		  'THREE' => 3,
	      );
	      apc_define_constants('numbers', $constants);
	      echo ONE, TWO, THREE;
	      ?>

	      The above example will output:

	      123

SEE ALSO

       apc_load_constants(3), define(3), constant(3),  Or the PHP constants reference.

PHP Documentation Group 												   APC_DEFINE_CONSTANTS(3)