www.digitalmars.com         C & C++   DMDScript  

digitalmars.D.learn - string vs. w/char*

reply "Tyro[a.c.edwards]" <nospam home.com> writes:
The bellow code attempts to use LoadStringA() to initialize _buf. 
However, regardless of what form _buf takes, the body of the if 
statement is always executed. I've attempted to use every type of string 
available in D to include char* _buf[MAX_RESSTRING+1] and setting 
_buf[MAX_RESSTRING] = '\0'; What am I doing incorrectly?
Any assistance is greatly appreciated.

class ResString
{
   enum { MAX_RESSTRING = 255 }
	
   alias getBuffer this;
    property string getBuffer() { return _buf; }

   this(HINSTANCE hInst, int resId)
   {
     _buf.length = MAX_RESSTRING;
	
     SetLastError(0);
		
     if(!LoadStringA(hInst, resId, cast(char*)toStringz(_buf), 
_buf.length + 1))
     {
       throw new WinException("Load String failed");
     }
   }

private:
   string _buf;
}
Feb 28 2011
parent reply "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Mon, 28 Feb 2011 07:34:39 -0500, Tyro[a.c.edwards] <nospam home.com>  
wrote:


 The bellow code attempts to use LoadStringA() to initialize _buf.  
 However, regardless of what form _buf takes, the body of the if  
 statement is always executed. I've attempted to use every type of string  
 available in D to include char* _buf[MAX_RESSTRING+1] and setting  
 _buf[MAX_RESSTRING] = '\0'; What am I doing incorrectly?
 Any assistance is greatly appreciated.

 class ResString
 {
    enum { MAX_RESSTRING = 255 }
 	
    alias getBuffer this;
     property string getBuffer() { return _buf; }

    this(HINSTANCE hInst, int resId)
    {
      _buf.length = MAX_RESSTRING;
 	
      SetLastError(0);
 		
      if(!LoadStringA(hInst, resId, cast(char*)toStringz(_buf),  
 _buf.length + 1))
      {
        throw new WinException("Load String failed");
      }
    }

 private:
    string _buf;
 }



You should not be overwriting buf, it is immutable.  You need to make a  
new buffer each time.

     this(HINSTANCE hInst, int resId)
     {

       auto mybuf = new char[MAX_RESSTRING];
       auto nchars = LoadStringA(hInst, resId, mybuf.ptr, mybuf.length);
       if(!nchars)
       {
         throw new WinException("Load String failed");
       }
       _buf = assumeUnique(mybuf[0..nchars]);
  	
       SetLastError(0);
     }

If this isn't working, you might consider that the string you are trying  
to load doesn't actually exist (that is a valid condition).  What is the  
error from GetLastError ?

-Steve
Feb 28 2011
next sibling parent reply "Tyro[a.c.edwards]" <nospam home.com> writes:
On 2/28/2011 9:58 PM, Steven Schveighoffer wrote:

 On Mon, 28 Feb 2011 07:34:39 -0500, Tyro[a.c.edwards] <nospam home.com>
 wrote:


 The bellow code attempts to use LoadStringA() to initialize _buf.
 However, regardless of what form _buf takes, the body of the if
 statement is always executed. I've attempted to use every type of
 string available in D to include char* _buf[MAX_RESSTRING+1] and
 setting _buf[MAX_RESSTRING] = '\0'; What am I doing incorrectly?
 Any assistance is greatly appreciated.

 class ResString
 {
 enum { MAX_RESSTRING = 255 }

 alias getBuffer this;
  property string getBuffer() { return _buf; }

 this(HINSTANCE hInst, int resId)
 {
 _buf.length = MAX_RESSTRING;

 SetLastError(0);

 if(!LoadStringA(hInst, resId, cast(char*)toStringz(_buf), _buf.length
 + 1))
 {
 throw new WinException("Load String failed");
 }
 }

 private:
 string _buf;
 }



 You should not be overwriting buf, it is immutable. You need to make a
 new buffer each time.

 this(HINSTANCE hInst, int resId)
 {

 auto mybuf = new char[MAX_RESSTRING];
 auto nchars = LoadStringA(hInst, resId, mybuf.ptr, mybuf.length);
 if(!nchars)
 {
 throw new WinException("Load String failed");
 }
 _buf = assumeUnique(mybuf[0..nchars]);

 SetLastError(0);
 }

 If this isn't working, you might consider that the string you are trying
 to load doesn't actually exist (that is a valid condition). What is the
 error from GetLastError ?

 -Steve



Both implementations results in error code 1812 being returned from 
GetLastError. explanation of the code reads:

      ERROR_RESOURCE_DATA_NOT_FOUND
      1812 (0x714)
      The specified image file did not contain a resource section.

The code I'm porting initially consisted of a resource.h file, a 
generic.rc file and two icons. I have not tried to include the icons and 
generic.rc file in the compilation because I do not know how to as yet 
and I've only used half of the resource.h file: didn't think I need the 
whole thing. Could this be the reason for the error? If so could you 
direct me to the explanation of how to prepare these files for inclusion 
in the compilation process?

Thanks,
Andrew
Feb 28 2011
parent reply J Chapman <jc ch.com> writes:
== Quote from Tyro[a.c.edwards] (nospam home.com)'s article

 Both implementations results in error code 1812 being returned from
 GetLastError. explanation of the code reads:
       ERROR_RESOURCE_DATA_NOT_FOUND
       1812 (0x714)
       The specified image file did not contain a resource section.
 The code I'm porting initially consisted of a resource.h file, a
 generic.rc file and two icons. I have not tried to include the icons and
 generic.rc file in the compilation because I do not know how to as yet
 and I've only used half of the resource.h file: didn't think I need the
 whole thing. Could this be the reason for the error? If so could you
 direct me to the explanation of how to prepare these files for inclusion
 in the compilation process?
 Thanks,
 Andrew



You need to compile the .rc file (see
http://www.digitalmars.com/ctg/rcc.html), then add the resulting .res file
to dmd's command line.
Feb 28 2011
parent reply "Tyro[a.c.edwards]" <nospam home.com> writes:
On 2/28/2011 11:08 PM, J Chapman wrote:

 == Quote from Tyro[a.c.edwards] (nospam home.com)'s article

 Both implementations results in error code 1812 being returned from
 GetLastError. explanation of the code reads:
        ERROR_RESOURCE_DATA_NOT_FOUND
        1812 (0x714)
        The specified image file did not contain a resource section.
 The code I'm porting initially consisted of a resource.h file, a
 generic.rc file and two icons. I have not tried to include the icons and
 generic.rc file in the compilation because I do not know how to as yet
 and I've only used half of the resource.h file: didn't think I need the
 whole thing. Could this be the reason for the error? If so could you
 direct me to the explanation of how to prepare these files for inclusion
 in the compilation process?
 Thanks,
 Andrew



 You need to compile the .rc file (see
 http://www.digitalmars.com/ctg/rcc.html), then add the resulting .res file
 to dmd's command line.



Awesome, this does the trick. However I get get a "GP Fault"? during 
execution. Using windbg, I tracked it down to this piece of code:

void Create()
{
   _hwnd = CreateWindowExA(
     _exStyle,
     cast(const(char*))_wc.GetName(), // returns string
     cast(const(char*))_windowName,   // string variable
     _style,
     _x,
     _y,
     _width,
     _height,
     _hWndParent,
     _hMenu,
     _wc.GetInstance(),
     _data);

     assert(_hwnd, "Internal error: Window Creation Failed.");
}

The program craps at assert() but the error is generated. It just 
displays a dialog box with the message: "test.exe has stopped working, 
Windows is checking for a solution to the problem..."

I'm thinking that _hwnd was never initialized and that assert is access 
a null pointer but I cannot be sure. Any suggestions or ideas?
Feb 28 2011
parent reply Tyro[a.c.edwards] <nospam home.com> writes:
== Quote from Denis Koroskin (2korden gmail.com)'s article

 On Mon, 28 Feb 2011 19:35:47 +0300, Tyro[a.c.edwards]




 wrote:

 On 2/28/2011 11:08 PM, J Chapman wrote:

 == Quote from Tyro[a.c.edwards] (nospam home.com)'s article

 Both implementations results in error code 1812 being













 GetLastError. explanation of the code reads:
        ERROR_RESOURCE_DATA_NOT_FOUND
        1812 (0x714)
        The specified image file did not contain a resource













 The code I'm porting initially consisted of a resource.h













 generic.rc file and two icons. I have not tried to include













 and
 generic.rc file in the compilation because I do not know how













 and I've only used half of the resource.h file: didn't think













 whole thing. Could this be the reason for the error? If so













 direct me to the explanation of how to prepare these files













 inclusion
 in the compilation process?
 Thanks,
 Andrew



 You need to compile the .rc file (see
 http://www.digitalmars.com/ctg/rcc.html), then add the










 file
 to dmd's command line.



 Awesome, this does the trick. However I get get a "GP Fault"?







 execution. Using windbg, I tracked it down to this piece of







 void Create()
 {
    _hwnd = CreateWindowExA(
      _exStyle,
      cast(const(char*))_wc.GetName(), // returns string
      cast(const(char*))_windowName,   // string variable
      _style,
      _x,
      _y,
      _width,
      _height,
      _hWndParent,
      _hMenu,
      _wc.GetInstance(),
      _data);

      assert(_hwnd, "Internal error: Window Creation Failed.");
 }

 The program craps at assert() but the error is generated. It







 displays a dialog box with the message: "test.exe has stopped







 Windows is checking for a solution to the problem..."

 I'm thinking that _hwnd was never initialized and that assert







 a null pointer but I cannot be sure. Any suggestions or ideas?




  cast(const(char*))_wc.GetName()







 const(char)*. Most importantly, the string (most likely) is not
 null-terminated.
 What you need to do here is the following:
 auto className = toStringz(_ws.GetName());
 auto caption = toStringz(_windowName);
 and pass those 2 to the function.



Actually I've already tried that, it has no effect on the outcome.
From your suggestion though, I've gone back and replace all the
cast(const(char*)) usage throughout the program. Final verdict:
the program still crashes it the same location. It actually never
returns from CreateWindowExA().


 Alternatively, you could make sure your strings are null-




 pass the pointer directly (e.g. _windowName.ptr):
 string _windowName = "foo"; // null-terminated automatically
 string _caption = ("Hello, World" ~ "\0")[0..$-1]; // append




 to an existing string but exclude it from result (so that it's




 included in _caption.length)
Feb 28 2011
parent reply Tyro[a.c.edwards] <nospam home.com> writes:
== Quote from Denis Koroskin (2korden gmail.com)'s article

 On Tue, 01 Mar 2011 02:08:48 +0300, Tyro[a.c.edwards]




 wrote:

 == Quote from Denis Koroskin (2korden gmail.com)'s article

 On Mon, 28 Feb 2011 19:35:47 +0300, Tyro[a.c.edwards]




 wrote:

 On 2/28/2011 11:08 PM, J Chapman wrote:

 == Quote from Tyro[a.c.edwards] (nospam home.com)'s article

 Both implementations results in error code 1812 being













 GetLastError. explanation of the code reads:
        ERROR_RESOURCE_DATA_NOT_FOUND
        1812 (0x714)
        The specified image file did not contain a resource













 The code I'm porting initially consisted of a resource.h













 generic.rc file and two icons. I have not tried to include













 and
 generic.rc file in the compilation because I do not know



















 to as yet

 and I've only used half of the resource.h file: didn't



















 I need the

 whole thing. Could this be the reason for the error? If so













 direct me to the explanation of how to prepare these files













 inclusion
 in the compilation process?
 Thanks,
 Andrew



 You need to compile the .rc file (see
 http://www.digitalmars.com/ctg/rcc.html), then add the










 file
 to dmd's command line.



 Awesome, this does the trick. However I get get a "GP













 during

 execution. Using windbg, I tracked it down to this piece of







 void Create()
 {
    _hwnd = CreateWindowExA(
      _exStyle,
      cast(const(char*))_wc.GetName(), // returns string
      cast(const(char*))_windowName,   // string variable
      _style,
      _x,
      _y,
      _width,
      _height,
      _hWndParent,
      _hMenu,
      _wc.GetInstance(),
      _data);

      assert(_hwnd, "Internal error: Window Creation













 }

 The program craps at assert() but the error is generated. It







 displays a dialog box with the message: "test.exe has













 working,

 Windows is checking for a solution to the problem..."

 I'm thinking that _hwnd was never initialized and that













 is access

 a null pointer but I cannot be sure. Any suggestions or













 The

  cast(const(char*))_wc.GetName()







 const(char)*. Most importantly, the string (most likely) is










 null-terminated.
 What you need to do here is the following:
 auto className = toStringz(_ws.GetName());
 auto caption = toStringz(_windowName);
 and pass those 2 to the function.



 Actually I've already tried that, it has no effect on the







 From your suggestion though, I've gone back and replace all the
 cast(const(char*)) usage throughout the program. Final verdict:
 the program still crashes it the same location. It actually







 returns from CreateWindowExA().


 Alternatively, you could make sure your strings are null-




 pass the pointer directly (e.g. _windowName.ptr):
 string _windowName = "foo"; // null-terminated automatically
 string _caption = ("Hello, World" ~ "\0")[0..$-1]; // append




 to an existing string but exclude it from result (so that it's




 included in _caption.length)










 I still think the parameters you are passing might be invalid.




 them to default values and see if that helps. Also try wrapping




 with a try/catch block and output an exception you are getting





The problem occurs at the site of the assertion. I wrapped the
function in a try/catch block and placed a call to MessageBoxA()
on either end of the the try block. Both calls to MessageBox fires
and the appropriate messages displayed. No exception is thrown:
made evident my the fact that the third call to MessageBox,
embeded in catch{}, is not fired. Nevertheless, execution haults
at the very next line following/catch and Create() never returns.
Mar 01 2011
parent reply Bekenn <leaveme alone.com> writes:
On 3/1/2011 12:25 AM, Tyro[a.c.edwards] wrote:

  Nevertheless, execution haults
 at the very next line following/catch and Create() never returns.



CreateWindow sends a few messages to your window proc; anything 
interesting happening there?
Mar 01 2011
parent reply "Tyro[a.c.edwards]" <nospam home.com> writes:
On 3/1/2011 7:18 PM, Bekenn wrote:

 On 3/1/2011 12:25 AM, Tyro[a.c.edwards] wrote:

 Nevertheless, execution haults
 at the very next line following/catch and Create() never returns.



 CreateWindow sends a few messages to your window proc; anything
 interesting happening there?



Not sure how to check those messages, but I guess that's a cue for me to 
do some more research. Off to Google land I go...
Mar 01 2011
parent reply "Tyro[a.c.edwards]" <nospam home.com> writes:
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit

On 3/1/2011 8:25 PM, Tyro[a.c.edwards] wrote:

 On 3/1/2011 7:18 PM, Bekenn wrote:

 On 3/1/2011 12:25 AM, Tyro[a.c.edwards] wrote:

 Nevertheless, execution haults
 at the very next line following/catch and Create() never returns.



 CreateWindow sends a few messages to your window proc; anything
 interesting happening there?



 Not sure how to check those messages, but I guess that's a cue for me to
 do some more research. Off to Google land I go...



After much searching, I've finally located the actual cause of the problem:

class TopWinClass: WinClass
{
	this(ushort resId, HINSTANCE hInst, WNDPROC wndProc)
	{
		super(resId, hInst, wndProc);
		SetResIcons(resId);
		wc.lpszMenuName = MAKEINTRESOURCEA(resId);  // [PROBLEM]
	}
}

The root cause of the problem begins with a lack of understanding of how 
to create a proper resource file for D. I simply took the C++ version, 
compiled it with rcc and linked it to my project: No changes whatsoever. 
Turn out that made the compiler/linker stop complaining, however 
MAKEINTRESOURCEA(resId) still cannot locate the correct resources or 
cannot properly use the resource it finds to initialize wc.lpszMenuName. 
Every access to wc.lpszMenuName after this point fails. If initialize 
wc.lpszMenuName with one of the default strings, say "STATIC" at this 
point, the program runs to completion. I've attached the resource file, 
it hopes that someone could help me with it's conversion.

Thanks.
Mar 03 2011
parent reply Kagamin <spam here.lot> writes:
Tyro[a.c.edwards] Wrote:


 class TopWinClass: WinClass
 {
 	this(ushort resId, HINSTANCE hInst, WNDPROC wndProc)
 	{
 		super(resId, hInst, wndProc);
 		SetResIcons(resId);
 		wc.lpszMenuName = MAKEINTRESOURCEA(resId);  // [PROBLEM]
 	}
 }
 
 Every access to wc.lpszMenuName after this point fails.



Who accesses it?

MAKEINTRESOURCEA just casts int to char* so it's an invalid pointer while still
valid resource indentifier, windows can differentiate them by zeroed high word.
Mar 04 2011
parent Kagamin <spam here.lot> writes:
Kagamin Wrote:


 Tyro[a.c.edwards] Wrote:
 

 class TopWinClass: WinClass
 {
 	this(ushort resId, HINSTANCE hInst, WNDPROC wndProc)
 	{
 		super(resId, hInst, wndProc);
 		SetResIcons(resId);
 		wc.lpszMenuName = MAKEINTRESOURCEA(resId);  // [PROBLEM]
 	}
 }
 
 Every access to wc.lpszMenuName after this point fails.



 Who accesses it?
 
 MAKEINTRESOURCEA just casts int to char* so it's an invalid pointer while
still valid resource indentifier, windows can differentiate them by zeroed high
word.



casts ushort to char*
Mar 04 2011
prev sibling next sibling parent "Steven Schveighoffer" <schveiguy yahoo.com> writes:
On Mon, 28 Feb 2011 08:30:02 -0500, Tyro[a.c.edwards] <nospam home.com>  
wrote:


 On 2/28/2011 9:58 PM, Steven Schveighoffer wrote:

 On Mon, 28 Feb 2011 07:34:39 -0500, Tyro[a.c.edwards] <nospam home.com>
 wrote:


 The bellow code attempts to use LoadStringA() to initialize _buf.
 However, regardless of what form _buf takes, the body of the if
 statement is always executed. I've attempted to use every type of
 string available in D to include char* _buf[MAX_RESSTRING+1] and
 setting _buf[MAX_RESSTRING] = '\0'; What am I doing incorrectly?
 Any assistance is greatly appreciated.

 class ResString
 {
 enum { MAX_RESSTRING = 255 }

 alias getBuffer this;
  property string getBuffer() { return _buf; }

 this(HINSTANCE hInst, int resId)
 {
 _buf.length = MAX_RESSTRING;

 SetLastError(0);

 if(!LoadStringA(hInst, resId, cast(char*)toStringz(_buf), _buf.length
 + 1))
 {
 throw new WinException("Load String failed");
 }
 }

 private:
 string _buf;
 }



 You should not be overwriting buf, it is immutable. You need to make a
 new buffer each time.

 this(HINSTANCE hInst, int resId)
 {

 auto mybuf = new char[MAX_RESSTRING];
 auto nchars = LoadStringA(hInst, resId, mybuf.ptr, mybuf.length);
 if(!nchars)
 {
 throw new WinException("Load String failed");
 }
 _buf = assumeUnique(mybuf[0..nchars]);

 SetLastError(0);
 }

 If this isn't working, you might consider that the string you are trying
 to load doesn't actually exist (that is a valid condition). What is the
 error from GetLastError ?

 -Steve



 Both implementations results in error code 1812 being returned from  
 GetLastError. explanation of the code reads:

       ERROR_RESOURCE_DATA_NOT_FOUND
       1812 (0x714)
       The specified image file did not contain a resource section.

 The code I'm porting initially consisted of a resource.h file, a  
 generic.rc file and two icons. I have not tried to include the icons and  
 generic.rc file in the compilation because I do not know how to as yet  
 and I've only used half of the resource.h file: didn't think I need the  
 whole thing. Could this be the reason for the error? If so could you  
 direct me to the explanation of how to prepare these files for inclusion  
 in the compilation process?



No clue, sorry.  I build D mostly on linux, on windows only when I have  
to.  Look on digitalmars.com for Windows programming.  Or try google.

-Steve
Feb 28 2011
prev sibling next sibling parent Andrej Mitrovic <andrej.mitrovich gmail.com> writes:
I've successfully used resource files with DFL. Maybe this will help:
http://www.dsource.org/forums/viewtopic.php?t=5591&sid=bf2d804f1d5a3f9efccbf29ebb6cf723

You'll have to dig into the DFL library sources to find out exactly
how it loads a resource file though.
Feb 28 2011
prev sibling next sibling parent "Denis Koroskin" <2korden gmail.com> writes:
On Mon, 28 Feb 2011 19:35:47 +0300, Tyro[a.c.edwards] <nospam home.com>  
wrote:


 On 2/28/2011 11:08 PM, J Chapman wrote:

 == Quote from Tyro[a.c.edwards] (nospam home.com)'s article

 Both implementations results in error code 1812 being returned from
 GetLastError. explanation of the code reads:
        ERROR_RESOURCE_DATA_NOT_FOUND
        1812 (0x714)
        The specified image file did not contain a resource section.
 The code I'm porting initially consisted of a resource.h file, a
 generic.rc file and two icons. I have not tried to include the icons  
 and
 generic.rc file in the compilation because I do not know how to as yet
 and I've only used half of the resource.h file: didn't think I need the
 whole thing. Could this be the reason for the error? If so could you
 direct me to the explanation of how to prepare these files for  
 inclusion
 in the compilation process?
 Thanks,
 Andrew



 You need to compile the .rc file (see
 http://www.digitalmars.com/ctg/rcc.html), then add the resulting .res  
 file
 to dmd's command line.



 Awesome, this does the trick. However I get get a "GP Fault"? during  
 execution. Using windbg, I tracked it down to this piece of code:

 void Create()
 {
    _hwnd = CreateWindowExA(
      _exStyle,
      cast(const(char*))_wc.GetName(), // returns string
      cast(const(char*))_windowName,   // string variable
      _style,
      _x,
      _y,
      _width,
      _height,
      _hWndParent,
      _hMenu,
      _wc.GetInstance(),
      _data);

      assert(_hwnd, "Internal error: Window Creation Failed.");
 }

 The program craps at assert() but the error is generated. It just  
 displays a dialog box with the message: "test.exe has stopped working,  
 Windows is checking for a solution to the problem..."

 I'm thinking that _hwnd was never initialized and that assert is access  
 a null pointer but I cannot be sure. Any suggestions or ideas?



The


  cast(const(char*))_wc.GetName()



line look *very* suspicious. You can't get a string and just cast it to  
const(char)*. Most importantly, the string (most likely) is not  
null-terminated.

What you need to do here is the following:

auto className = toStringz(_ws.GetName());
auto caption = toStringz(_windowName);

and pass those 2 to the function.

Alternatively, you could make sure your strings are null-terminated and  
pass the pointer directly (e.g. _windowName.ptr):

string _windowName = "foo"; // null-terminated automatically
string _caption = ("Hello, World" ~ "\0")[0..$-1]; // append trailing zero  
to an existing string but exclude it from result (so that it's not  
included in _caption.length)
Feb 28 2011
prev sibling parent "Denis Koroskin" <2korden gmail.com> writes:
On Tue, 01 Mar 2011 02:08:48 +0300, Tyro[a.c.edwards] <nospam home.com>  
wrote:


 == Quote from Denis Koroskin (2korden gmail.com)'s article

 On Mon, 28 Feb 2011 19:35:47 +0300, Tyro[a.c.edwards]




 wrote:

 On 2/28/2011 11:08 PM, J Chapman wrote:

 == Quote from Tyro[a.c.edwards] (nospam home.com)'s article

 Both implementations results in error code 1812 being













 GetLastError. explanation of the code reads:
        ERROR_RESOURCE_DATA_NOT_FOUND
        1812 (0x714)
        The specified image file did not contain a resource













 The code I'm porting initially consisted of a resource.h













 generic.rc file and two icons. I have not tried to include













 and
 generic.rc file in the compilation because I do not know how













 and I've only used half of the resource.h file: didn't think













 whole thing. Could this be the reason for the error? If so













 direct me to the explanation of how to prepare these files













 inclusion
 in the compilation process?
 Thanks,
 Andrew



 You need to compile the .rc file (see
 http://www.digitalmars.com/ctg/rcc.html), then add the










 file
 to dmd's command line.



 Awesome, this does the trick. However I get get a "GP Fault"?







 execution. Using windbg, I tracked it down to this piece of







 void Create()
 {
    _hwnd = CreateWindowExA(
      _exStyle,
      cast(const(char*))_wc.GetName(), // returns string
      cast(const(char*))_windowName,   // string variable
      _style,
      _x,
      _y,
      _width,
      _height,
      _hWndParent,
      _hMenu,
      _wc.GetInstance(),
      _data);

      assert(_hwnd, "Internal error: Window Creation Failed.");
 }

 The program craps at assert() but the error is generated. It







 displays a dialog box with the message: "test.exe has stopped







 Windows is checking for a solution to the problem..."

 I'm thinking that _hwnd was never initialized and that assert







 a null pointer but I cannot be sure. Any suggestions or ideas?




  cast(const(char*))_wc.GetName()







 const(char)*. Most importantly, the string (most likely) is not
 null-terminated.
 What you need to do here is the following:
 auto className = toStringz(_ws.GetName());
 auto caption = toStringz(_windowName);
 and pass those 2 to the function.



 Actually I've already tried that, it has no effect on the outcome.
 From your suggestion though, I've gone back and replace all the
 cast(const(char*)) usage throughout the program. Final verdict:
 the program still crashes it the same location. It actually never
 returns from CreateWindowExA().


 Alternatively, you could make sure your strings are null-




 pass the pointer directly (e.g. _windowName.ptr):
 string _windowName = "foo"; // null-terminated automatically
 string _caption = ("Hello, World" ~ "\0")[0..$-1]; // append




 to an existing string but exclude it from result (so that it's




 included in _caption.length)






This is indeed strange, but it has nothing to do with the function itself.  
I still think the parameters you are passing might be invalid. Try setting  
them to default values and see if that helps. Also try wrapping the call  
with a try/catch block and output an exception you are getting (if any).
Feb 28 2011