C / C++ / MFC

29-Mar-08 4:55

Hello everyone,

Here is my precompiled header settings,

--------------------
Create/Use PCH Through File stdafx.h
PreCompiled Header File .\Debug/client.pch
--------------------

1.

It means all the content before stdafx.h will be precompiled into client.pch? So that each time compiler "assumes" the content before stfafx.h will not be changed. Right?

2.

How will compiler solve this situation?

// in file foo.c
#include "foo.h"
#include "stdafx.h"

// in file goo.c
#include "goo.h"
#include "stdafx.h"

Compiler will pre-compile foo.h, goo.h and stdafx.h into one client.pch file? Or pre-compile foo.h + stdafx.h into one file, and pre-compile goo.h and stdafx.h into another file?

thanks in advance,
George

Mark Salsbery29-Mar-08 7:24

Mark Salsbery

29-Mar-08 7:24

The compiler will ignore the included file above stdafx.h...

You should get a warning as well, something like

warning C4627: '#include <foo.h>': skipped when looking for precompiled header use

To do something like that negates the usefulness of a precompiled header anyway....why would you do it?

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

George_George29-Mar-08 22:47

29-Mar-08 22:47

Thanks Mark,

I am reading MSDN definition for the file name parameter from,

http://msdn2.microsoft.com/zh-cn/library/7zc28563(en-us).aspx
[^]

here is the meaning for the file parameter from MSDN,

--------------------
Specifies a header (.h) file. When this argument is used, the compiler
compiles all code up to and including the .h file.
--------------------

For exmaple, we have a file like this,

// section 1
include "stdafx.h"
// section 2

1. Does it mean when we compile the file, only stdafx.h and section 2 are compiled?
2. Or does it mean when compiler do the precompile, section 1 and stdafx.h will be pre-compiled into some .pch file?

regards,
George

rp_suman29-Mar-08 23:04

29-Mar-08 23:04

Hi,

AFAIK, it is a rule that every cpp file in program should include "stdafx.h" and also it should be in the first line before including any other header.

Best Regards,
Suman

--
"Programming is an art that fights back!"

George_George29-Mar-08 23:33

29-Mar-08 23:33

Thanks Suman,

For my previous post,

http://www.codeproject.com/script/Forums/View.aspx?fid=1647&msg=2485956[^]

Do you think my understanding (1) is correct or (2) is correct or neither is correct (if so, please help to give your understanding. Smile | :)

)?

regards,
George

rp_suman30-Mar-08 0:59

30-Mar-08 0:59

Hi,

I am not sure, I think as Mark said, whatever in the "section1" will be ignored and remaining will be compiled.

You can check it by using some mathmatics functions in your cpp file and include the "math.h" before "stdafx.x", you may get error.

Best Regards,
Suman

--
"Programming is an art that fights back!"

George_George30-Mar-08 1:05

30-Mar-08 1:05

Thanks Suman,

For the pre-compile phase to generate pre-compiled headers (.pch), is only stdafx.h used to generate the client.pch or both section 1 and stdafx.h are used to generate the client.pch?

(you can check my original post for more details about context)

regards,
George

Mark Salsbery30-Mar-08 7:59

Mark Salsbery

30-Mar-08 7:59

There's a third compiler option you need to work with here

/Yc Create precompiled header
/Yu Use precompiled header

If you look closely at the settings for a wizard-generated Visual C++ project,
ONE source file uses the /Yc option to create the precompiled header....this is typically
stdafx.cpp. All the other source files use the /Yu compiler option, to use the precompiled
header.

The "Create/Use PCH through file" option has two uses -
1) when used with /Yc, it specifies the file to stop precompilation on (at the end of)
2) when used with /Yu, it specifies the file to replace with the precompiled header

This has the following effects if "stdafx.h" is the "Create/Use PCH through file" setting:
1) For the file compiled with the /Yc option, everything included before and through the stdafx.h file
is compiled into a precompiled header file.
2) For any files compiled with the /Yu option, everything included before and through the stdafx.h file
is ignored and replaced with the precompiled header file.

Hopefully I explained that OK.

More info here: /Yu (Use Precompiled Header File)[^]

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

George_George30-Mar-08 23:12

30-Mar-08 23:12

Thanks Mark!

I read through the wonderful reply and information referred by you. I think in my case, I need to creat two pre-compiled files since for each source file, the pre-compiled information are different, right?

regards,
George

Mark Salsbery31-Mar-08 5:28

Mark Salsbery

31-Mar-08 5:28

George_George wrote:
I think in my case, I need to creat two pre-compiled files since for each source file, the pre-compiled information are different, right?

First, I'm not sure how well that works, but you could easily try it.

But a precompiled header is really meant for common definitions - e.g. CRT headers, Windows SDK headers, app-common classes, etc.

For anything that varies between source files, those should be included separately, and in fact, must be.

The precompiled header is available just for efficiency, so the compiler doesn't have to waste extra time compiling the same
exact items for every source file.

I personally have never encountered a case where I needed to have more than one PCH file like you're showing, with differing
include files above the precompiled header.

The standard PCH usage...

// stdafx.h
...#includes and definitions used by all modules go in here


// stdafx.cpp  (compiled with /Yc)
#include "stdafx.h"


//sourcefile1.cpp  (compiled with /Yu)
#include "stdafx.h"  // first include the PCH
#include <math.h>    // now include headers specific to this module
#include <vfw.h>
...


//sourcefile2.cpp  (compiled with /Yu)
#include "stdafx.h"  // first include the PCH
#include <vector>    // now include headers specific to this module
#include <string>
...

...always works fine for me.

Mark

Mark Salsbery
Microsoft MVP - Visual C++
Java | [Coffee]

George_George31-Mar-08 18:27

steps reqd to connect from VC++9 to oracle?

31-Mar-08 18:27

Thanks for your advice, Mark!

I think I need to merge them into one pch file.

regards,
George

Kashineni29-Mar-08 4:47

Kashineni

29-Mar-08 4:47

Hi I would like to Know the steps reqd to connect from VC++9 to oracle?

Cheers

Re: steps reqd to connect from VC++9 to oracle?

rp_suman29-Mar-08 6:52

29-Mar-08 6:52

Hi,

The solution could be something similar to here: Using OCCI with Microsoft Visual C++[^]

An article in CP Oracle connection and cursor class for Visual C++ in a VB Style[^]

Best Regards,
Suman

--
"Programming is an art that fights back!"

Problem of MENUBAR?

Le@rner29-Mar-08 2:15

Le@rner

29-Mar-08 2:15

Hi all,

I m working on VC++2005, and my application is SDI type.

when i run my application in MENUBAR the option of Print and print preview are disabled.

any one can tell me how can enable them.

Thanks in advance

Re: Problem of MENUBAR?

rp_suman29-Mar-08 2:34

Problem of load icon in dialog box.

29-Mar-08 2:34

Hi,

Is this discussion helpful: print handler[^]?

Best Regards,
Suman

--
"Programming is an art that fights back!"

Le@rner29-Mar-08 2:11

Le@rner

29-Mar-08 2:11

Hi all,

i have an problem in load icon for sub-dialog box.

i want to show main application icon on subdialog box or internal dialog box of application.

i m using this.

HICON m_hIcon = AfxGetApp()->LoadIcon(IDR_MAINFRAME);

where IDR_MAINFRAME is icon of main application.but it not works.

anyone can help me.

thanks in advance

Re: Problem of load icon in dialog box.

rp_suman29-Mar-08 2:25