• Sam Hu (24/24) Sep 03 2009 Given below code(Win32 SDK):
• Sam Hu (1/1) Sep 03 2009 Sorry.Under dmd2.031 ,windows XP
• Max Samukha (8/37) Sep 03 2009 I guess MessageBox checks if the pointer to the message text is NULL. If...
• div0 (22/59) Sep 03 2009 -----BEGIN PGP SIGNED MESSAGE-----
• Sam Hu (9/9) Sep 03 2009 Hi both:

Sam Hu <samhudotsamhu gmail.com> writes:

Given below code(Win32 SDK):

int /*LRESULT*/ wndProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
	{
		switch(msg)
		{
							case WM_LBUTTONDOWN:
				{
					wchar* szFileName=cast(wchar*)(new wchar[1024]);// ***questioned line
										HINSTANCE hInstance=GetModuleHandleW(null);
					GetModuleFileNameW(hInstance,szFileName,1024);
					MessageBoxW(null,cast(const wchar*)szFileName, "Full Path:",
					MB_ICONINFORMATION);
				}
				
				break;
}

My program runs OK and can print the exe path as expected.But if I change 
wchar* szFileName=cast(wchar*)(new wchar[1024]);

to 
wchar* szFileName;

The program runs also but prints blank.Why?

Thanks for your help in advance.
Regards,
Sam

Sam Hu <samhudotsamhu gmail.com> writes:

Sorry.Under  dmd2.031 ,windows XP

Max Samukha <spambox d-coding.com> writes:

Sam Hu wrote:

 Given below code(Win32 SDK):
 
 int /*LRESULT*/ wndProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
 {
 switch(msg)
 {
 case WM_LBUTTONDOWN:
 {
 wchar* szFileName=cast(wchar*)(new wchar[1024]);// ***questioned line
 HINSTANCE hInstance=GetModuleHandleW(null);
 GetModuleFileNameW(hInstance,szFileName,1024);
 MessageBoxW(null,cast(const wchar*)szFileName, "Full Path:",
 MB_ICONINFORMATION);
 }
 
 break;
 }
 
 My program runs OK and can print the exe path as expected.But if I change
 wchar* szFileName=cast(wchar*)(new wchar[1024]);
 
 to
 wchar* szFileName;
 
 The program runs also but prints blank.Why?
 
 Thanks for your help in advance.
 Regards,
 Sam

I guess MessageBox checks if the pointer to the message text is NULL. If it 
is NULL, it prints nothing.

You should check the return value of GetModuleFileName. It may fail for 
various reasons. I guess it fails if you pass a null pointer to it.

Also, you don't have to call GetModuleHandle to get the handle of the 
calling process' module. Just pass NULL as first argument to 
GetModuleFileName.

div0 <div0 users.sourceforge.net> writes:

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Max Samukha wrote:
 Sam Hu wrote:
 
 Given below code(Win32 SDK):

 int /*LRESULT*/ wndProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
 {
 switch(msg)
 {
 case WM_LBUTTONDOWN:
 {
 wchar* szFileName=cast(wchar*)(new wchar[1024]);// ***questioned line
 HINSTANCE hInstance=GetModuleHandleW(null);
 GetModuleFileNameW(hInstance,szFileName,1024);
 MessageBoxW(null,cast(const wchar*)szFileName, "Full Path:",
 MB_ICONINFORMATION);
 }

 break;
 }

 My program runs OK and can print the exe path as expected.But if I change
 wchar* szFileName=cast(wchar*)(new wchar[1024]);

 to
 wchar* szFileName;

 The program runs also but prints blank.Why?

 Thanks for your help in advance.
 Regards,
 Sam

 
 I guess MessageBox checks if the pointer to the message text is NULL. If it 
 is NULL, it prints nothing.
 
 You should check the return value of GetModuleFileName. It may fail for 
 various reasons. I guess it fails if you pass a null pointer to it.

Exactly; MSDN is your friend:

http://msdn.microsoft.com/en-us/library/ms683197(VS.85).aspx

The szFileName parameter is a pointer to a buffer that
GetModuleFileNameW *fills*. As you've passed a null pointer,
there is no buffer to fill.

The fact your program isn't crashing when you call MessageBox is because
windozes checks for it.

Which arguably it shouldn't. If it had crashed it would probably have
helped you work out what was wrong.

- --
My enormous talent is exceeded only by my outrageous laziness.
http://www.ssTk.co.uk
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Sam Hu <samhudotsamhu gmail.com> writes:

Hi both:

Thank you so much for your help!

ps:just found other than write :

wchar* szFileName=cast(wchar[])(new wchar[1024);

It works also if I write:
wchar[1024] szFileName;

I am annoying everytime when pass D strings to/from OS API...

Regards,
Sam