[fpc-pascal] Cannot find entry point of a routine inside a windows 64 dll

[Dennis]

Sven Barth via fpc-pascal wrote:
> On 15.12.2017 16:10, Dennis wrote:
>>> Okay, that explains things a bit more.
>>>
>>> May I ask you to provide a small example consisting of program and
>>> library (source only) that works in 32-bit, but fails in 64-bit? Try
>>> way I can check myself what is going on as I have a Delphi starter on
>>> my 64-bit Windows as well. Though it will be the weekend till I'll
>>> have the time to look at it.
>> Sven,
>>
>> Attached is a zipped file containing the Caller program and Callee dll.
>> Both Compiled ok in windows 32 but when running Caller.exe, it reported
>> the error.
>>
>> Thanks a lot.
> There were two adjustments I had to do to make it work correctly:
>
> - add {$mode objfpc} to Caller.lpr as I was compiling from the commandline
> - adjust the casing of ReOpenExcelWorkBook so that it matched the one
> from ReopenExcelWorkBook (these are case sensitive!)
>
> With these changes it worked without problem on win64.
>
> That said you might want to apply the following two points to your
> library interface:
> - export/import functions/procedures using explicit names (extending
> "external LibName" to "external LibName name 'ProcName'" for each
> routine to import and adding "name 'ProcName'" for each routine in the
> exports section) to be sure that no name mangling interferes here
> - add an explicit calling convention to each routine for import and
> export (you could use "register", the default calling convention since
> Delphi and FPC *should* be compatible here, but "stdcall" would be my
> suggestion to be on the save side)
>
> Additionally you can check for any discrepancies using the Dependency
> Walker ( http://www.dependencywalker.com/ ). Just open the executable
> while the library is located in the same directory and you can see which
> routines mismatch.
>
> Regards,
> Sven


Thank you so much!!!

Dennis