[Lazarus] WinINet STDCALL callback crash

[Hans-Peter Diettrich]

matthew at accordancebible.com schrieb:
> Hello Lazarus Community,
> 
> I am implementing asynchronous file download using WinINet's STDCALL
> callback.  However, when the callback function recursively calls
> itself, it generates a crash around fpc_popaddrstack.

Recursive asynchronous calls deserve special handling. They should be 
avoided in the first place, nowadays *threads* can be used instead.

>  I hypothesize
> that Pascal does not understand how to handle callbacks that use the
> stdcall convention (which I must use since the callback interfaces
> with the Win32 API and is itself set via the Win32 WinINet procedure
> InternetSetStatusCallback).

This IMO is not a language problem, but misuse of asynchronous processing.

> I was wondering if anyone might graciously offer guidance on how to
> implement asynchronous download to file using the Win32 API or
> associated libraries only.

I'd suggest to move the download into an thread, and use synchronous 
processing there.

DoDi