[gdal-dev] Thread safety of GDAL projection machinery?

[Karney, Charles]

Thanks for the reply.

> At first sight, you're likely doing things the right way and probably
> discovered a bug related to multi-threading in GDAL. The use of
> GDALCreateGenImgProjTransformer() should be thread-safe (provided that you
> don't use the same dataset in the different threads)

Yes, each thread is dealing with a separate set of files.

> By reviewing the code of 2 files that are used in the retrieving and parsing
> of the csv files, there are a few variables that are supposed to be
> thread-local (CPL_THREADLOCAL), but this is currently a no-op.
>
> But as it's just a guess and maybe not the real cause for your problems,
> ideally, you could file a bug in the GDAL Trac with a small program that
> reproduces your issue, so that it can be investigated further.

It's probably going to be tough for me to carve out a test case.
However, can I turn the question around?  If CPL_THREADLOCAL is a noop,
how can the code in cpl_csv.cpp possibly be thread safe?

In the meantime, I've put a lock around by GDAL calls which avoids the
errors (but probably with penalty in performance).

--
Charles Karney <ckarney at sarnoff.com>
Sarnoff Corporation, Princeton, NJ 08543-5300

Tel: +1 609 734 2312
Fax: +1 609 734 2662