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Maybe my examples weren't best chosen. As the article I referred to points out, the position of the const qualifier can become significant when you introduce a pointer or reference. So although "const int" and "int const" are identical, "const int*" and "int* const" are not. The first is a pointer to a const int, while the second is a const pointer to a non-const int.
Of course, you might not make this error if you separate the pointer from the type, because "const int *" and "int const *" are also identical in meaning.
Thinking in terms of always putting const to the right of what you are making const would help to avoid this sort of confusion.
Now, if you are using typedefs, it can be more confusing still:
typedef int * PINT;
typedef const PINT CPINT;
typedef const int * PCINT;
It might be "reasonable" to expect, when attempting to understand line 2 that the type defined in line 3 would be identical, because all we've done is substitute "int *" for the typedef PINT - but the result is not the same. However, if you adopt the "const to the right" convention, then making that direct substitution does work:
typedef int * PINT;
typedef PINT const CPINT;
typedef int * const CPINT;
Of course, you could say that you'll never write such a typedef, but the typedef could be created by someone else within a template - Loki makes use of typedefs in its Typelists, for example - and if you're not using the "const to the right" convention then it will be harder to understand and debug any resulting issues.
So yes, it is a style issue, but there is at least one specific circumstance in which it will commonly lead to an incorrect understanding of the way C++ works, and poor understanding leads directly to bugs.
What I was really hoping for were some opinions as to whether an improvement in long term understandability of code justified the short term confusion that would be inevitable by overturning a long-standing convention?
Reference: "C++ Templates - The Complete Guide", David Vandevoorde and Niccolai Josuttis.
There is also a short article (c.1998), available somewhere online, which seems to have been the first to raise this issue, but unfortunately I haven't managed to find it again to provide a link.
Gavin Greig
"Haw, you're no deid," girned Charon. "Get aff ma boat or ah'll report ye."
Matthew Fitt - The Hoose O Haivers: The Twelve Trauchles O Heracles.
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I am trying to convert a service skeleton to unicode and I have run into a problem with the event logging. The function void CService::LogEvent(LPCSTR pFormat, ...) and has problems with parsing arguments. This is the original code that compiles under MBCS:
void CService::LogEvent(LPCSTR pFormat, ...)
{
TCHAR chMsg[256];
...
va_list pArg;
va_start(pArg, pFormat);
vsprintf(chMsg, pFormat, pArg);
va_end(pArg);
...
printf(chMsg);
}
so the following code will output Text=1
DWORD dw=1;
LogEvent("Text=%d", dw);
My code:
void CService::LogEvent(LPCSTR pFormat, ...)
{
TCHAR chMsg[256];
...
va_list pArg;
va_start(pArg, pFormat);
vswprintf(chMsg, (LPCTSTR)pFormat, pArg);
va_end(pArg);
...
printf("%s", chMsg);
}
will output Text=%d
I can't just print straight out each time because the LogEvent uses the chMsg string differently when its running as a services vs. a console app. Does anyone have an suggestions?
Matt
BURN HIM! - David Wulff
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Ummm, having trouble finding a well defined question. 
However that aside, if you are using TCHAR then you should also use a #define'd version of vsprintf i.e. _vstprintf().
Also, you might actually want to use _vsntprintf() instead to help prevent buffer overrun.
I'm not sure what you were asking with regard to the printf() statement.
...cmk
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cmk wrote:
Ummm, having trouble finding a well defined question.
Oh, sorry. My problem was that instead of formating the DWORD value into the string, it was just printing the %d and ignoring the value.
Matt
BURN HIM! - David Wulff
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Matt Newman wrote:
cmk wrote:
Ummm, having trouble finding a well defined question.
Oh, sorry. My problem was that instead of formating the DWORD value into the string, it was just printing the %d and ignoring the value.
Matt
Oh yes, i see what you were asking now.
The problem is likely that you are passing in straight char* "Text=%d" and yet using the unicode version which will expect ALL string parameters to be unicode.
Using the TCHAR is an all or nothing proposition.
Wrap all literal strings with _T() e.g. _T("Text=%d").
Personally i gave up on using all that as there were cases when i needed both ansi and unicode strings.
...cmk
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I made a simple Windows application written in MFC that uses CHtmlView to render HTML pages and everytime it navigates to a page containing an applet, the application uses Microsoft's VM, even if the Internet Options has been set to use "Java 2 for <applet>". Sun's VM is used as expected when the same page is navigated from Internet Explorer.
Does anyone know how to get an application that extends the CHtmlView class to behave similarly to Internet Explorer and use Sun's Java? Thanks.
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Does anyone know of a good reference on using a Rich Edit control 2.0 in a dialog application written in C. Currently if I place a rich edit box in my applicatoin is does not start but if I remove the rich edit control from the dialog form the application starts. Not sure what I am doing wrong? Any help would be most appreciated. If someone has some sample code the use Rich Edit box in c, it will be a great help.
Regards,
SAK
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What you need to do is call AfxInitRichEdit() in your app's
InitInstance() function.
jhaga
CodeProject House, Paul Watson wrote:
...and the roar of John Simmons own personal Nascar in the garage. Meg flitting about taking photos.Chris having an heated arguement with Colin Davies and .S.Rod. over egian values. Nish manically typing *censur*. Duncan racing around after his pet *c.* Michael Martin and Bryce loudly yelling *c.* C.G. having a fit as Roger Wright loads up *c.* . Anna waving her *c.* and Deb scoffing chocolates in the corner.
...Good heavens!
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Jhaga,
Thank you for the reply, I think AfxInitRichEdit is only is used when programming MFC, at least that is what the MSDN documentation seemed to say. Do I need to include a particular library, header? Is there an equivalent in 'c'. I tried search through google...can find much on programming richedit in c.
Regards,
SAK
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How do you know if a combination of a path and filename is valid ?
I don't want to know if it is an actual existing file but only if it's valid (does not contain any invalid caracters). Also, I do not want to create a file on the disk to know if I'll receive an invalid filename error.
So, how can I know if a path + filename combination has a valid syntax ?
(example: "C:\folder name\file name.ext" is valid, "C:\folder name\file&?n!.ext" is invalid)
I'm using C++ only (no MFC, etc).
Thanks a lot !
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=
J.-C. Gauthier - http://www.grandmenhir.com/
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One solution is to create a temporary file or path.
Kuphryn
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Unfortunately, I do not want to do that (like mentionnend in the original post) Its a possible solution but I would like to use only if everything else should fail
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Testing is the only programming solution.
Kuphryn
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This article titled "Making Room for Long Filenames" in the location "Windows Base Services General Technical Articles " of the MSDN Library has a few general guidelines for long filenames, and they include:
- The application must not use the following characters in directory names or filenames, because they are reserved for Windows:
< > : " / \ |
- The application must not use reserved words, such as aux, con, and prn, as filenames or directory names.
The documentation forgot to mention that asterisk (*) and the question mark (?) are also invalid characters.
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I might soon need to write an Extensible Authentication Protocol (EAP) and wondered if there is anyone out there that has done this...
I've got the VS6 sample that implements a simple password request response protocol and that looks pretty straightforward but MSDN also mentions a further sample in the section entitled Server-Side Configuration User Interface that would show an ATL implementation of IEAPProviderConfig - does anyone know where I can get hold of this sample.
If there's anyone out there that's implemented an EAP dll then any tips that would be really appreciated.
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im trying to use ImageMagick with MS Vision SDK.
there are a few problems that i have
[1] i am trying to run the demo project from Imagemagick 5.5.6
i have linked the following folders to the project:
C:\Projects\ImageMagick\Magick++\lib
C:\Projects\ImageMagick\Magick++
C:\Projects\ImageMagick\magick
but i still get the following error:
c:\projects\imagemagick\magick++\lib\magick++\include.h(13) : fatal
error C1083: Cannot open include file: 'magick/magick_config.h': No
such file or directory
any ideas??
[2] i need some advice about using both MS vision SDk and ImageMagick together. is there certain versions of Image Magick that will only work with MS vision SDk? and how would i link the image resize class from ImageMagick with a MS Vision Project?
Elaine
elaine_clancy@hotmail.com
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Hi,
I have a dialog with a bitmap background. On my dialog I have many controls, some of them are radio buttons. My problem is that when I use radio buttons, my background is not updated. Unstead, I have white rectangles around my radio buttons.
So I would like that my radio buttons let me see my bitmap.
any ideas?
thanks
Everything's beautiful if you look at it long enough...
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I have a C++ class as a part of a COM object which is as follows :
typedef struct {
int currentSize;
int currentIndex;
int requestedAddress;
short requestedType;
string requestFunction;
UINT8 *buffer ;
} AomMemoryParameters;
I add a type of this struct as a private member .
AomMemoryParameters currentParams;
Now in a private function
when I try to do
currentParams.currentIndex=0;
currentParams.currentSize=0;
I get a runtime error . I am unable to figure out what the error is
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Post the IDL code for the structure.
Kuphryn
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I have a program that accesses a PCI card and reads data in memory on the card.
I am trying to convert the program so that the data that is in memory on the card can be displayed in various textfields and other widgets.
Should I do this with the MFC WIZZARD APP or should I choose another type of project?
Is there any project that allows me to choose from a list of widgets and place them where I want them?
My Boss wants me to use Borland and I have been using it, but the driver for the card is written in VC++. I'm sure as you know the 2 don't work well together.
If I can come up with a good solution using VC++ then I won't have to mess with Borland again.
Thanks for the help,
sj
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a) Your expectations for MFC are a bit high. You'd be better of with C#, or Borland C++ if you know it already.
If "driver" means the OS driver, it really doesn't matter which language it's written in. You might need to do some adjustments to the code that does access the device, but basically, it should port reasonably between Borland and VC.
You can create a dialog based MFC application (using the MFC app wizard), which probably gets closest to your expectations. However, as much as MS touted it, MFC is no real RAD tool, and you're up for some serious learning.
"Der Geist des Kriegers ist erwacht / Ich hab die Macht" StS
sighist | Agile Programming | doxygen
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Sounds like you are familuar with VC++ and Borland. I know borland fairly well and already have the GUI layed out. And the *.lib file converted to BC++B format. I just can't seem to get it to connect with the card. That is where I assume it has to do with the dll file that links to the card.
Would using the WTL be eaisier creating a widget type GUI?
At least with VC++ I have code project for some help.
I can't seem to find a decent Borland Builder forum anywhere. I have been using their news group but it takes about 24 hours to get a reply.
Does anyone know of a good Borland Builder forum?
All of your help is greatly appreciated.
sj
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I don't have much experience with the late borland, However, I have *lots* of frustrating experience with MFC, and I know that a tool you know is always easier than one you don't.
WTL could be easier if you're used to raw Win32 programming, because WTL is fairly transparent (compared to the often smoke and mirrors MFC). However, WTL is far from RAD either (I assume you don't have much Windows experience beyond OWL just because you want to "place widgets". Placing them is easy, wiring them is not)
Try to get some documentation on the DLL. Might just be some declarations / function import stuff.
Your Borland does 32bit windows, right? (The last borland I touched was Win16...)
"Der Geist des Kriegers ist erwacht / Ich hab die Macht" StS
sighist | Agile Programming | doxygen
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You are right, I don't have too much experience with windows. I would much rather place wigets than wire them in.
I am going to keep pounding at this connection problem until it's figured out.
I was looking for a way out of the problem. I guess by other ways than figureing it out.
Maybe I'll eat a bananna.
I appreciate the help.
cheers,
sj
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johnstonsk wrote:
Maybe I'll eat a bananna.
You're welcome.
Neither Windows nor MFC are "complicated voodoo magic", however, I'm always wary if someone thinks that an unknown tool will magically solve the problems with known tools...
"Der Geist des Kriegers ist erwacht / Ich hab die Macht" StS
sighist | Agile Programming | doxygen
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