Basically, any heap memory access and standard pascal I/O are forbidden in
threads started outside FPC, because the necessary thread structures are not
initialized correctly.
Michael.
On Mon, 12 Jul 2010, Alexander Grau wrote:
Hello,
While using an external C framework (Mac OS X, discrecording OS framework,
FPC 2.4), I noticed that my FPC console app crashes when I use writeln's in
both C threads (callbacks).
Example: Two FPC functions that are called from an external C library
(c_callback1 and c_callback2) - callback2 is called within callback1 in
another C thread (other than the FPC main thread).
// called from external C framework within the FPC main thread
c_callback1; cdecl;
begin
writeln('callback1begin');
// c_ callback2 is called here from another C thread
writeln('callback1end'); <== my FPC console app crashes here (
"EInOutError - Disk Full")
end;
// called from external C framework in another C thread
c_callback2; cdecl;
begin
writeln('callback2begin');
writeln('callback2end');
end;
An unhandled exception occurred at $000669E3 :
EInOutError : Disk Full
$000669E3 CALLBACK1, line xxx
Question: Why isn't it safe to call writeln's in non-FPC threads? Are
there any other FPC runtime functions I should not call within non-FPC
threads?
I'm going to make an FPC wiki page ('Threading Pitfalls') that will discuss
these and other issues related to threading and I welcome all explanations on
this so I can better understand this problem! :-)
Thanks,
Alexander
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