[fpc-pascal] USB Human Interface Devices

[Stefan V. Pantazi]

Libusb can be compiled with either calling convention - one just has to 
be sure which one.
In https://github.com/Zaaphod/libusbxhid/blob/master/libusbx.pas (line 
35), the windows calling convention is stdcall and that apparently works 
for both 64 and 32 bit windows. So, James' libusb10 dlls use stdcall.

Also, I was under the impression that unlike linux, Windows apps would 
compile regardless of the calling convention. Only when launching the 
app and loading a dynamic library a wrong calling convention make things 
blow up. Anyway, this is definitely something to look into.

On 8/17/19 11:46 AM, Jean SUZINEAU wrote:
> Le 17/08/2019 à 17:10, Stefan V. Pantazi a écrit :
>> The obvious first thing to make sure is that the calling convention 
>> matches the library for the platform. I see that in 
>> https://github.com/Zaaphod/pas-libusb/blob/Hack/src/libusb.pas 9line 46)
>> the calling convention on Windows is cdecl (the stdcall is commented 
>> out). In libusbxhid, if I remember correctly, the calling convention 
>> for windows dlls is set to stdcall.
> Yes it's curious.
> 
> Usually with Microsoft dlls from the Windows API, you use stdcall. Here 
> with stdcall I get an error "Import library not found  for  libusb-1.0".
> 
> So I commented out the stcall changed it to cdecl.
> 
> This allows to compile without errors and test1library.pas works without 
> error, it seems cdecl is the right calling convention for libusb-1.0.
> 
>> One other thing is that debugging is much more tedious without an 
>> integrated debugger that allows you to step through each line before 
>> you can see which function call blows up with a segfault.
> James works on the command line but fp.exe seems to integrate gdb.exe 
> the same way that lazarus does, you nearly have the same shortcuts keys 
> for debugging between Turbo Pascal 5.5, fp.exe and lazarus ...
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