[fpc-pascal] linking and using dynamic libraries on amd64

[Marc Santhoff]

On Do, 2015-02-12 at 09:03 +0000, Tony Whyman wrote:
> Marc,
> 
> If your running on a *nix system then you probably want "cdecl" rather
> than "stdcall"

Err ... you're right and it is cdecl. I have mixed it up because it is
an $if_n_def ...:

...;{$ifndef Win32}cdecl{$else}stdcall{$endif};external libname name 'xxx';

If I find the time I'll go on and investigate the exact position the
error occurs. Maybe it is possible to build it with debugging symbols,
in code I have to find a way throug the macro djungle ... one reason to
use Object Pascal.

Thanks for waking me up. ;)

Marc

> On 12/02/15 04:54, Marc Santhoff wrote:
> > On Do, 2015-02-12 at 00:42 +0100, Marc Santhoff wrote:
> >> Hi,
> >>
> >> when I try to run a program that dynamically links an external .so
> >> library it throws a SIGSEGV error at startup. That seems to happen while
> >> loading the library before any code of mine is exeuted.
> >>
> >> The library is pulled into it by a header translation from C to Pascal.
> >> The functions are declared "...; stdcall; external libname name xxx'.
> >> This way it worked on i386.
> >>
> >> When the error occurs the ASM window pops up, which is not very helpful
> >> for me.
> >>
> >> There may be a minor change in the lib source itself, but compiling the
> >> header and linking works OK. I have no idea how to check besides getting
> >> the older versions source and try again. Will try if nothing else is
> >> fishy.
> > I did test the old library and the error is the same.
> >
> > GDB tells me it happens when starting at BEGIN and running the init function
> > of the library. That function does not have any arguments, I'm assuming
> > "something else" then ...
> >
> >> My questions:
> >>
> >> Is there any difference in declaring external functions between 32 and
> >> 64 bit mode?
> >>
> >> How can I debug what is happening? Will compiling the library having an
> >> external debug file work when debugging from Lazarus?
> >>
> >> Any hints for diagnosing what's going wrong are very welcome.
> >>
> >>
> >>
> >> Some data points:
> >> fpc 2.6.2 x86_64
> >> library is compiled to 64 bit
> >> FreeBSD 9.1-STABLE amd64
> >>
> >> Best regards,
> >> Marc 
> >>
> 
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-- 
Marc Santhoff <M.Santhoff at web.de>