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Full Discussion: Class Pointer initialization C++
Top Forums Programming Class Pointer initialization C++ Post 302519627 by sidorenko on Wednesday 4th of May 2011 12:20:16 PM
Old 05-04-2011
as far as I remember, in
Code:
ClassA * point;
point = new ClassA;

`new' will allocate memory for exactly one object of type `ClassA' and yield the address of the 1-st memory cell at which the definition of the object will start. In
Code:
ClassA *point;
point = 0;

you're not creating any object at all but just explictily stating that the pointer `point' will point to the zero-th cell. In that case your pointer merely becomes the so called `null pointer' - a special kind of pointers which do not point to any valid memory address.

I might err, so please correct me, if I'm wrong

---------- Post updated at 11:20 AM ---------- Previous update was at 11:20 AM ----------

as far as I remember, in
Code:
ClassA * point;
point = new ClassA;

`new' will allocate memory for exactly one object of type `ClassA' and yield the address of the 1-st memory cell at which the definition of the object will start. In
Code:
ClassA *point;
point = 0;

you're not creating any object at all but just explictily stating that the pointer `point' will point to the zero-th cell. In that case your pointer merely becomes the so called `null pointer' - a special kind of pointers which do not point to any valid memory address.

I might err, so please correct me, if I'm wrong
 

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LEARN ABOUT HPUX

tt_message_user

tt_message_user(library call)											     tt_message_user(library call)

NAME

       tt_message_user -- retrieve the user information associated with a message object

SYNOPSIS

       #include <Tt/tt_c.h>
       void *tt_message_user(
       Tt_message m,
       int key);

DESCRIPTION

       The tt_message_user function retrieves the user information stored in data cells associated with the specified message object.

       The  user data is part of the message object (that is, the storage buffer in the application); it is not a part of the actual message.  The
       application can, therefore, only retrieve user information that the application placed in the message.

       The m argument is the opaque handle for the message involved in this operation.	The key argument is the user data cell	to  be	retrieved.
       The user data cell must be unique for this message.

RETURN VALUE

       Upon  successful completion, the tt_message_user function returns the data cell, a piece of arbitrary user data that can hold a void *. The
       application can use tt_ptr_error(3) to extract one of the following Tt_status values from the returned data:

       TT_OK	 The operation completed successfully.

       TT_ERR_NOMP
		 The ttsession(1) process is not running and the ToolTalk service cannot restart it.

       TT_ERR_POINTER
		 The pointer passed does not point to an object of the correct type for this operation.

APPLICATION USAGE

       The application should use tt_free(3) to free any data stored in the address returned by the ToolTalk API.

       The user data cell is intended to hold an address.  If the address selected is equal to one of the Tt_status enumerated values, the  result
       of the tt_ptr_error(3) function will not be reliable.

SEE ALSO

       Tt/tt_c.h - Tttt_c(5), tt_ptr_error(3), tt_free(3).

														     tt_message_user(library call)
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