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digitalmars.D.learn - Problems when using DLL-Functions

reply =?ISO-8859-15?Q?Marc_M=FCller?= <dont spam.me> writes:
Hello,

I wrote a small program, which is using a function from a Windows 
system-dll.
So I used the implib-tool to get a corresponding library-file:

implib.exe /s wintab32.lib C:\WINDOWS\system32\Wintab32.dll

I can call functions from the dll correctly and also get the expectet 
return values. But under some circumstances the application crashes - 
and I just don't know why...


=========================================================
import std.stdio;
import std.c.windows.windows;

extern(C)
UINT WTInfoA(UINT, UINT, LPVOID);

version = A;

void main(char[][] args)
{
	version (A)
	{
		writefln("Getting WTInfo...");
		WTInfoA(0, 0, null);
		writefln("Received WTInfo");
	}

	version (B)
	{
		writefln("Getting WTInfo...");
		int value = WTInfoA(0, 0, null);
		writefln("Received WTInfo");
	}

	version (C)
	{
		try
		{
			writefln("Getting WTInfo...");
			WTInfoA(0, 0, null);
			writefln("Received WTInfo");
		}
		catch (Exception e)
		{
			writefln("An error has occured:");
			writefln(e.msg);
		}
	}

	version (D)
	{
		if (WTInfoA(0, 0, null)==0)
			writefln("No graphic tablet available");
	}
}
=========================================================


Now the funny part:

As you can see all versions A-D are doing more or less the same.

Version A crashes with the following output:
# Getting WTInfo...
# Received WTInfo
# Error: Access Violation

Version B works fine.
# Getting WTInfo...
# Received WTInfo

Version C (which is identical to version A - just surrounded by a 
try-catch-block) does neither crash nor it throws an exception.
# Getting WTInfo...
# Received WTInfo

Version D, which also evaluates the return-Value from the function call 
like version B crashes.
# Error: Access Violation


I think anything is scrambling my stack - but it is absolutely 
unpredictable when this occurs - and I have no clue what I can do :-(

The errors are reproducable - Version A always crashes while version B 
never crashes.

Do you have an Idea?

Kind regards,
	-Marc-
Jul 09 2007
next sibling parent reply torhu <fake address.dude> writes:
Marc Müller wrote:

 extern(C)
 UINT WTInfoA(UINT, UINT, LPVOID);



Try extern (Windows) instead of extern (C) here.


 I think anything is scrambling my stack - but it is absolutely 
 unpredictable when this occurs - and I have no clue what I can do :-(
 
 The errors are reproducable - Version A always crashes while version B 
 never crashes.
 
 Do you have an Idea?



The stack getting scrambled is a tell-tale sign of using the wrong 
calling convention.  I can't find WTInfoA on msdn.com, but I'm guessing 
it's a stdcall function.
Jul 09 2007
parent =?ISO-8859-15?Q?Marc_M=FCller?= <dont spam.me> writes:
torhu schrieb:

 Marc Müller wrote:

 extern(C)
 UINT WTInfoA(UINT, UINT, LPVOID);



 Try extern (Windows) instead of extern (C) here.



Thanks for the hint. When I try extern(Windows) the Compiler/Linker 
complains:

Error 42: Symbol Undefined _WTInfoA 12


Listing the content of the lib-file with

libunres.exe -e -p wintab32.lib

results in:
...
_WTInfoA
...

	-Marc-
Jul 09 2007
prev sibling parent BLS <nanali nospam-wanadoo.fr> writes:
Marc Müller schrieb:

 Hello,
 
 I wrote a small program, which is using a function from a Windows 
 system-dll.
 So I used the implib-tool to get a corresponding library-file:
 
 implib.exe /s wintab32.lib C:\WINDOWS\system32\Wintab32.dll
 
 I can call functions from the dll correctly and also get the expectet 
 return values. But under some circumstances the application crashes - 
 and I just don't know why...
 
 
 =========================================================
 import std.stdio;
 import std.c.windows.windows;
 
 extern(C)
 UINT WTInfoA(UINT, UINT, LPVOID);
 
 version = A;
 
 void main(char[][] args)
 {
     version (A)
     {
         writefln("Getting WTInfo...");
         WTInfoA(0, 0, null);
         writefln("Received WTInfo");
     }
 
     version (B)
     {
         writefln("Getting WTInfo...");
         int value = WTInfoA(0, 0, null);
         writefln("Received WTInfo");
     }
 
     version (C)
     {
         try
         {
             writefln("Getting WTInfo...");
             WTInfoA(0, 0, null);
             writefln("Received WTInfo");
         }
         catch (Exception e)
         {
             writefln("An error has occured:");
             writefln(e.msg);
         }
     }
 
     version (D)
     {
         if (WTInfoA(0, 0, null)==0)
             writefln("No graphic tablet available");
     }
 }
 =========================================================
 
 
 Now the funny part:
 
 As you can see all versions A-D are doing more or less the same.
 
 Version A crashes with the following output:
 # Getting WTInfo...
 # Received WTInfo
 # Error: Access Violation
 
 Version B works fine.
 # Getting WTInfo...
 # Received WTInfo
 
 Version C (which is identical to version A - just surrounded by a 
 try-catch-block) does neither crash nor it throws an exception.
 # Getting WTInfo...
 # Received WTInfo
 
 Version D, which also evaluates the return-Value from the function call 
 like version B crashes.
 # Error: Access Violation
 
 
 I think anything is scrambling my stack - but it is absolutely 
 unpredictable when this occurs - and I have no clue what I can do :-(
 
 The errors are reproducable - Version A always crashes while version B 
 never crashes.
 
 Do you have an Idea?
 
 Kind regards,
     -Marc-



Ahem,
If not allready done; Have a look t the D Forum , it seems that our D - 
Debugger developer -Jascha Wetzel- found a solution.
Bjoern
That s about suggestion something :-(
Jul 09 2007