[Proposal/Testing Request] Use WIN32 mutex locks on Windows

[Konstantin Podsvirov]

Different builds based on mingw/clang available now for libspatialite and spatialite-tools via MSYS2 distro.

Suggested (patch in builds) changes is described in Ticket.

Please check the available builds and report if there are any problems.

PS: Alessandro, can we discuss themes like this in this list?

--

Regards,

Konstantin Podsvirov

[Alessandro Furieri]

Hi Konstantin,

> PS: Alessandro, can we discuss themes like this in this list?

>

why not ? we'll immediately start

just few quick comments about your proposed patch:

1. using semaphores was strictly required by older versions

   of GEOS that weren't safely reentrant thus causing endless

   troubles to multithreded applications.

   but starting from GEOS v.3.5.0 (released on August 2015)

   GEOS is now fully reentrant, so these portions of code

   are no longer useful and are still preserved just not to

   break legacy support for obsolete versions of GEOS

   (please look at the conditional GEOS_REENTRANT set by  

   ./configure)

   

2. the basic idea was to use libpthread on Linux and MinGW

   switching to the Windows native CriticalSection only

   when using the MSVC compiler.

   

3. I've never used the clang compiler on Windows, but I 

   easily imagine that it has problems in supporting

   libpthreads; do you confirm ?

   

short conclusion: always using the Windows native

semaphores instead of the ones supported by pthreads

seems to be a more portable solution.

I've absolutely no objections in this case (mainly

because we are talking about "dead code" no longer

required), but I'm afraid for other libraries like 

librasterlite2 that make a wider use of multithreading. 

switching from libpthread to Windows native support 

could be a little bit harder.

just for my personal curiosity, please explain in

more depth where are the troubles for the clang

compiler.

bye Sandro

[Konstantin Podsvirov]

Answer from original PR:

clang on windows can support libpthreads, via the winpthreads package from mingw-w64, same as GCC. But, the clang prefixes here are configured so that libc++ uses native windows threads instead, so winpthreads is not pulled along automatically by things linking to the C++ runtime as it is with gcc.

среда, 11 августа 2021 г. в 19:45:30 UTC+3, Alessandro Furieri: