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1. I didn't copy the whole code, just the snippet.
2. Yes, I did. That's how I could state 'it stays as NULL before and after the call'.
3. I do. Thanks.
4. Same reason as number 1 above.
Anyway, I solved it as pointed by CPallini below. I was missing the ampersand symbol to indicate passing by pointer. Thanks anyway.
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If you want to change the passed pointer value then you have to pass its address (because, like any other kind of parameter, pointers are passed by value) ending up with a double pointer or a reference to the pointer. e.g.
void CMyApp::CallDlg(int nType, CMyDlg & * pDlg)
void CMyApp::CallDlg(int nType, CMyDlg * & pDlg)
{
}
modified 17-May-16 15:57pm.
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Ah, you are right. To pass by address, I need the & character. It's working fine now. Thanks so much.
void CMyApp::CallDlg(int nType, CMyDlg* &pDlg)
{
}
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I gave you a flawed code sample, sorry. 
Thank you for pointing it out so nicely.
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if I have this code :
char * s =(char*)malloc(10);
and then I write 's="test"' then s will have a different address right ?
why is this happening ?
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You are allocating assigning the address of the string literal "test" to the pointer s thus overwriting the address returned by malloc. You should be using strcpy to copy the four characters into the allocated buffer.
[edit]
better terminology as pointed out by member below.
[/edit]
modified 17-Jun-16 4:11am.
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or, even better, strncpy.
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Absolutely right, but I was trying to KISS.
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Shouldn't that be: "you are assigning the address" instead of allocating?
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Member 10964099 wrote: why is this happening ?
It append because it designed this way. That is how pointers work.
I recommend to read THE book "the C Language" from Kernigan & Ritchie.
The C Programming Language - Wikipedia, the free encyclopedia[^]
Patrice
“Everything should be made as simple as possible, but no simpler.” Albert Einstein
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Because s is a pointer.
char * s =(char*)malloc(10);
s="test"
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What all the others said and more generally rarely if ever do use an equal sign on a string in C at any other time than creation.
There are functions required to add, copy, compare, split and search strings and you can't just use mathematical symbols like "=" and "+" to do things with strings like you can in some higher languages. Strings are not mathematical types and you can't use mathematical functions to do things with them.
Those coming from a coding background in Java or Basic tend to do what you did and you have to unlearn it when using C because "string1" + "string2" will not work either, you will need to use strcat functions. String compares are likewise a function and you can't use mathematical equality signs to compare two strings.
Learning the string functions, it is a requirement of learning the C language.
In vino veritas
modified 14-May-16 12:10pm.
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inside a C function I have this code
printf("%s",final);
I do a fork and this is part of the childs code
the final string is not printed when the execl line is not commented out,nor are any printf calls before it
why is this happening ?
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Without seeing more code it is anyone's guess.
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Probably due to line buffering.
Try
printf("%s\n", final); or add
fflush(stdout); before the execl() call;
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If your on Eclipse it is a known bug (id=173732)
The fflush(stdout); fix is the only way around it as horrible as it is.
In vino veritas
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Windows 7 UAC prevents my application to write log data in the installation folder. The original text log file exists from the very beggining, but its empty.
When I start my app with the -L parameter to start logging, it does not write anything due the UAC control. If I rum my app with Admin Priviledges then it works.
As you can understand I can not suggest my client to run the app with right click and "run as an Administrator".
Is there any solution for that ?
Best Regards,
sdancer75
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Yes - don't try to write files in the installation folder. Your application will not have permission to do so.
Instead, create a folder for your application under one of the AppData locations - CSIDL_APPDATA, CSIDL_LOCAL_APPDATA or CSIDL_COMMON_APPDATA - and write the log files to that folder.
CSIDL (Windows)[^]
SHGetFolderPath function (Windows)[^]
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Thank you
Is that backward compatible with windows xp/vista ?
I think that win Xp does not support AppData. Is that correct ? What to do in this case ? Check the os and take a path decision specifically for it ?
sdancer75
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It should be supported in XP - the folder was called "Application Data" / "Local Data" back then.
They changed it to "AppData\Roaming" and "AppData\Local" in Vista to reduce the chances of code breaking the 260-character path limit. Similarly, the "Documents and Settings" folder was renamed to "Users".
"These people looked deep within my soul and assigned me a number based on the order in which I joined."
- Homer
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Thank you for your help 
Best Regards,
sdancer75
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This break in CWnd::WindowProc randomly appears when running my application(originally released in 2010 and runs 24/7 in many places) in debug. In release mode it crashes.
The message type is always 874(x36A).
The only true call backs I have are for custom draw list boxes and typically when I have an error in those routines MFC catches and breaks at that point. Obviously that are countless other messages processed.
I am trying to determine A: what is message 874? and B: what circumstances cause it to be posted (though A may answer B)?
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I cannot find the specific message number in Winuser.h in VS 2013, but I did find the following two lines:
#define WM_AFXFIRST 0x0360
#define WM_AFXLAST 0x037F
Googling for WM_AFXFIRST came up with: WM_AFXFIRST - Google Search[^].
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Thanks - I found those two - Jochen below narrowed it down.
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