string vs. w/char*

[Denis Koroskin]

On Tue, 01 Mar 2011 02:08:48 +0300, Tyro[a.c.edwards] <nospam at home.com>  
wrote:

> == Quote from Denis Koroskin (2korden at gmail.com)'s article
>> On Mon, 28 Feb 2011 19:35:47 +0300, Tyro[a.c.edwards]
> <nospam at home.com>
>> wrote:
>> > On 2/28/2011 11:08 PM, J Chapman wrote:
>> >> == Quote from Tyro[a.c.edwards] (nospam at 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.
>
> 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-
> 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)
>

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).