Re^2: Correct call for dll with Win32::API

[walto]

This is the line from the sample C-code:
int HCE300_Read(int TrackNo, char *ReadData);

I have no readable documentation of the dll. The data is read from an usb device. Re-reading the documentation of Win32::API I changed the line to:

my $readdevice = Win32::API->new (
                    'HCE300_API.DLL', 'HCE300_Read','NP','N') or die $
+^E;
if(not defined $readdevice) {
        die "Can't import API HCE_Read: $!\n";
    }

I am not sure what it does, but it did not help. Perl still crashes.

[ikegami]

If int HCE300_Read(int TrackNo, char *ReadData); is the prototype, then it uses the default calling convention. It my understanding that's __cdecl for MS compilers. Win32::API uses the __stdcall calling convention since that's what the Win32 API (kernel32.dll, etc) uses.

	Argument-passing order	Stack-maintenance responsibility
__stdcall	Right to left	Called function pops its own arguments from the stack
__cdecl	Right to left	Calling function pops the arguments from the stack

Win32::API expects the DLL function to reset the stack, but the DLL function expects its caller to reset the stack.

[walto]

Thanks for your help and patience with my lack of C, but does this mean I can not use Win32::API?

[BrowserUk]

Do you have dumpbin.exe on your system? If so, could you post the output from the command:

dumpbin /exports HCE300_API.DLL

[ikegami]

If there's a difference in calling conventions, yes. Unresolvable protocol differences.

It could be a number of other things too.

• You have the wrong prototype.
• You are using the library in a manner it doesn't expect.
• There's a bug in the library.
• etc.