Am 25.10.2018 um 17:38 schrieb Karoly Balogh (Charlie/SGR):
Hi,
On Thu, 25 Oct 2018, Michael Van Canneyt wrote:
- Make Exception handling, TLS etc use the infrastructure that
libpthread is providing
TLS is handled already by libpthread. I doubt you will gain much there.
GCC has (depending on the platform) a faster implementation for "__thread"
variables. E.g. on x86 it uses the GS segment and the data is stored in ELF
sections. There were experiments in the past to support this in FPC as
well, so maybe we're on a good way there already.
That is good news. The contours of a TODO list are becoming visible :)
But we may need also need a solution for other platforms, which means the
current system should remain in place for those platforms where such a
system is not present ?
FPC already has some code to support section threadvars via the GS segment
on i386 at least, but it doesn't seem to be enabled by default? (Couldn't
test it, but the tf_section_threadvars target flag, which enable this is
actually behind a define in i_linux.pas, which I couldn't find enabled
anywhere?). Also tf_section_threadvars flag has some code to support it
all over the compiler, including the x86 cg. I have some really vague
memories I actually enabled it in some experimental local version I had,
and it worked on first sight at least, but I could be completely off here.
I wonder why it was never enabled by default.
The %gs based approach works only for object files linked statically to
the executable. In general there are four TLS access models on linux and
at least three of them need to be supported, if one wants to support
dyn. libraries in a usefull manner. Of course, this comes with the
requirement to over means to control the used model. The tls.pdf by U.
Drepper decribes it very well.
_______________________________________________
fpc-devel maillist - [email protected]
http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
