[Lazarus] Editing a TDBf record

[Dave Coventry]

Mark Morgan Lloyd wrote:

> ...
> When compiled for Linux I've got a simple unit UsbIf that calls Uwe 
> Zimmerman's translation of libusb.h which includes
> 
> {$linklib usb}
> ..
> procedure usb_set_debug(level: longint);cdecl;external;
> 
> On the Windows systems the DLL is libusb0.dll and in principle I've got 
> .h files etc. available. When I compile I get
> 
> Error: Import library not found for usb
> ..
> Error: Undefined symbol _usb_set_debug
> 
> It's 20 years since I've played with import libraries, and before I 
> start tinkering I need to know that I'm not heading off in the wrong 
> direction.

Having faced with the same problem in the meantime, I deleted the 
{$linklib } directive and added library and name to all function 
definitions, so your example would look like

procedure usb_set_debug(level: longint);cdecl;external libname name 
'usb_set_debug';

The libname constant has to be defined differently for Windows and Linux:

const
{$IFDEF MSWINDOWS}
   libname = 'libusb0.dll';
{$ELSE}
   libname = 'libusb.so';
{$ENDIF}

Another caveat with libusb-win32 is that LIBUSB_PATH_MAX constant should 
be different from the Linux one:

{$IFDEF MSWINDOWS}
const LIBUSB_PATH_MAX = 512;
{$ENDIF}
{$IFDEF LINUX}
const LIBUSB_PATH_MAX = 4097;
{$ENDIF}

Regards,
Sergei