[fpc-devel] Threading support and C library under Linux/Unix

[Henry Vermaak]

On 22 June 2010 16:15, Marco van de Voort <marcov at stack.nl> wrote:
> In our previous episode, Henry Vermaak said:
>> > The cure is ten times more difficult than the problem. (namely that the
>>
>> That seems quite clear.
>>
>> > Libc breaks often, but I'm sure that a native lib will break much more
>>
>> I certainly haven't experienced this libc that breaks often.
>
> Keep in mind that that is defined in the context of cross-distro
> compatibility of the binary interface.
>
> This because we only have one source, and don't automatically adapt to
> differences.
>
> So if only one distro e.g. starts increasing time_t to 64-bit, it is considered
> broken (we can't have a binary distro that works everywhere) till all
> distros have adopted time_t to 64-bit. Gentoo is usually the distro that is
> first with such changes btw.
>
> Only one such change in 2 years, but that takes its time to ripple through
> to all distros can already cause effective "breakage" half of the time.
>
> Besides that there is the reference distribution problem. This goes even a
> step further, and not only requires that something from FPC source, linked
> on target is working on all distros, but requires that the reference FPC
> release (the .tgz on linux, nearly all, binaries are libc free atm) works on
> all distros, and can be used as a base for bootstrapping.  This breaks as
> soon as a binary linked on one distro doesn't work on the other.
>
> Even renaming a library breaks this, since it will not exist on the other
> platform.
>
>> Does that mean that our linux threading will also break often because we
>> rely on libc for that?  Again, I haven't seen this, either.
>
> Its not the threading, but the fact that if _something_ that you use from
> libc, or the link process _TO_ libc leads to an incompatible binary.
>
> As far as threading goes, post NTPL (which hurt pretty bad btw), I can
> vaguely remember some problems related to sem_timedwait.

Thanks for the explanation, it all makes a bit more sense, now!

Henry