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Jon Sagara wrote:
When doing comparisons, put the constant value on the LHS of the comparison operator:
Quote/Unquote 'Debugging Windows Application' Microsoft Press 
Regards
Ray
"Je Suis Mort De Rire"
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Yep, it's in there, too. 
Jon Sagara
"We assume you already know not to consider something like Windows as a firewall platform. Does the name "Windows" evoke images of security? Silly rabbit, Windows is for desktops." -- Unix System Administration Handbook
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Jon Sagara wrote:
When doing comparisons, put the constant value on the LHS of the comparison operator:
if (NULL == m_pPointer)
If you happen to accidentally leave off one of the equal signs (i.e., NULL = m_pPointer), your code won't compile because you can't assign a value to a literal.
Here's a better tip:
Write it in the readable fashion, as you did, eg:
if (m_pointer == NULL)
and then use the following pragma to prevent assignments in the body of an if statement:
#pragma warning(error : 4706) // Assignment in conditional
This keeps your code readable and safe at the same time. And while the pragma is not portable, the resulting safe, readable code is.
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Jim A. Johnson wrote:
if (NULL == m_pPointer)
I didn't realize that this was non-portable. It has worked for me using VC6 and the GNU compilers.
Also, what is so difficult to read? I actually prefer this method because I know right away what the value of the variable is supposed to be.
Jon Sagara
"We assume you already know not to consider something like Windows as a firewall platform. Does the name "Windows" evoke images of security? Silly rabbit, Windows is for desktops." -- Unix System Administration Handbook
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He meant the #pragma that disallows assignments in if conditions is non-portable.
--Mike--
http://home.inreach.com/mdunn/
#include "witty_sig.h"
![Heart | [heart]](https://codeproject.freetls.fastly.net/script/Forums/Images/love.gif) your ![Green Alien | [Alien]](https://codeproject.freetls.fastly.net/script/Forums/Images/alien.gif) with ![Good Stuff | [The good stuff]](https://codeproject.freetls.fastly.net/script/Forums/Images/vegemite.gif) and ![Beer | [beer]](https://codeproject.freetls.fastly.net/script/Forums/Images/beer.gif)
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Context - The Mother of all Flame Wars.
Thanks for the note Michael,
Jon Sagara
"We assume you already know not to consider something like Windows as a firewall platform. Does the name "Windows" evoke images of security? Silly rabbit, Windows is for desktops." -- Unix System Administration Handbook
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Jon Sagara wrote:
I didn't realize that this was non-portable. It has worked for me using VC6 and the GNU compilers
That's not what I said. Read it again, please.
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This keeps your code readable and safe at the same time. And while the pragma is not portable, the resulting safe, readable code is.
Misunderstanding. My bad. Please forgive me this one transgression. 
Just out of curiosity, why don't you consider if (NULL == m_pPointer) readable? I admit it looked strange to me at first, but it's such a simple coding trick that you can use to save debugging time without having to remember some obscure pragma directive.
Jon Sagara
"We assume you already know not to consider something like Windows as a firewall platform. Does the name "Windows" evoke images of security? Silly rabbit, Windows is for desktops." -- Unix System Administration Handbook
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Yeah, I agree. It is all about just getting use to it.
Tim Smith
Descartes Systems Sciences, Inc.
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Why not use:
if (!m_pPointer)
instead of
if (NULL == m_pPointer)
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Because the second is instantly readable, whereas with the first one you have to remember that "!pointer" means "pointer is not zero".
--Mike--
http://home.inreach.com/mdunn/
#include "witty_sig.h"
your with and
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I agree with Mike, but I would make it
if (m_pPointer == NULL)
instead.
It just looks better to me because it flows more like the way you speak the same phrase. I've never heard anyone say "If NULL is the pointer...", but instead, people say "If the pointer is NULL...".
"...the staggering layers of obscenity in your statement make it a work of art on so many levels." - Jason Jystad, 10/26/2001
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void NewPointer()
{
if (m_pPointer == NULL)
{
m_pPointer = new(MyCPointClass);
if (NULL != pPointer && m_pPointer->NewPoint()) // NewPoint is a function, right?
{
return;
}
else
{
delete(m_pPointer);
m_pPointer = NULL; // avoid deleting the memory twice! deleting a NULL pointer is safe, but has a performance penalty since a call to the C-runtime library is done.
}
}
}
void DeletePointer()
{
if (NULL != m_pPointer)
{
delete m_pPointer;
m_pPointer = NULL;
}
}
if you insert
m_pPointer = NULL
somewhere in your code between NewPointer() and DeletePointer(), then yes you have a memory leak.
--------------------------------------------------
If my messages appear curt, I apologize.
I try to be brief to save your time as well as mine.
--------------------------------------------------
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I would just like to say thanks to everybody for their response, all the answers were superb. I just didn`t think to delete the pointer first and then assign it NULL, but everything fits perfectly in my head now. I wondered how the application could delete those pointers in my program that were unused, without any trouble and it was because I had assigned them all to NULL in the constructor! For some reason I thought delete, deleted the memory AND set it to NULL, thats why I couldn`t grasp how it was actually working. But thanks to everyone who wrote in, I am very grateful,
Cheers,
Alan.
P.S. I liked the tips too. Just when I think I seem to be mastering this language, someone comes along and goes "Here's a better way of going about it...", that always amazes me. Thanks for those too guys.
"When I left you I was but the learner, now I am the Master" - Darth Vader
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pls
==============
www.design.kg
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use this
ShellExecute(this->m_hWnd,"open","mailto:","","",SW_SHOW);
Nish
Sonork ID 100.9786 voidmain
www.busterboy.org
Nish is a BIG fan of Goran Ivanisevic
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?
==============
www.design.kg
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you need to open the following registry key
HKEY_CLASSES_ROOT\mailto\shell\open\command
Nish
Sonork ID 100.9786 voidmain
www.busterboy.org
Nish is a BIG fan of Goran Ivanisevic
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(1) open the key HKEY_CLASSES_ROOT\mailto\shell\open\command
(2) read it default value. I got this when I did that here
"%ProgramFiles%\Outlook Express\msimn.exe" /mailurl:%1
(3) you need to replace %ProgramFiles% with the actual path
for that use SHGetSpecialFolderLocation and SHGetSpecialFolderPath [you'll find samples in CP]
(4) forget the /mailurl:%1 part
(5) shellexecute the rest of it
Nish
Sonork ID 100.9786 voidmain
www.busterboy.org
Nish is a BIG fan of Goran Ivanisevic
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Hello, the codegurus around the world.;)
Have a nice day!
-Masaaki Onishi-
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Do you need a DLL's source code to generate .tbl or in there some tool that will extract a .tbl file from a .dll ?
I was importing (declaring) functions from a .dll (you may know it RAPI.dll, it comes with MS ActiveSync) into VB software, the functions didn't work and kept returning wierd error values. I tracked down a web site, which offered a copy of a .tbl which described the .dll I was attempting to use. Once registered I had no problem using the .dll . Can someone tell me what was going on ?
Regards
Ray
"Je Suis Mort De Rire"
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Did you try registering the dll?
regsvr32 xxx.dll
Glad you found a solution, its nice to be talking hypothetically instead of urgently.
Bill
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It seems to be a Com component, its Export Table has all the apropriate functions etc. But I can't registry it ... What is a .tbl file, where does it come from ?
Regards
Ray
"Je Suis Mort De Rire"
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.tbl files are type libraries. They are created when an activeX control is built. They contain all the information regarding an objects interfaces. ActiveX controls are somewhat different than ordinary dlls, in that there is a lot more control excercised over the calling of exported functions.
If you look at your project, you will see some additional files created when you build it using the .tbl. It should create a .c file containing helper functions. Your program calls the helpers, which in turn call Invoke in the control, telling it which method (exported function) to invoke.
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