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

[Charles Karney]

I have a multi-threaded application with reads the geodata out of many
files using GDAL.

For each image, it calls

  GDALCreateGenImgProjTransformer(// Source
				  dataset,GDALGetProjectionRef(dataset),
				  // Dest (NULL means dest is geo)
				  NULL, WGS84.c_str(),
				  // Don't use GCPs
				  0, 0, 0 );

and I then compute the lat/long of the 4 image corners.

I call

    GDALAllRegister();

before entering the multi-threaded portion of the code.

With files that require that pcs.csv be read, I get the following error
messages

    ERROR 3: Read of file c:/Program Files (x86)/FWTools2.2.8/data/pcs.csv failed.
    ERROR 3: Read of file c:/Program Files (x86)/FWTools2.2.8/data/pcs.csv failed.
    ERROR 2: CPLRealloc(): Out of memory allocating 1956 bytes.
    ERROR 3: Read of file c:/Program Files (x86)/FWTools2.2.8/data/pcs.csv failed.
    ERROR 3: Read of file c:/Program Files (x86)/FWTools2.2.8/data/pcs.csv failed.
    ERROR 3: Read of file c:/Program Files (x86)/FWTools2.2.8/data/pcs.csv failed.
    ERROR 3: Read of file c:/Program Files (x86)/FWTools2.2.8/data/pcs.csv failed.
    ERROR 3: Read of file c:/Program Files (x86)/FWTools2.2.8/data/datum.csv failed.
    ERROR 3: Read of file c:/Program Files (x86)/FWTools2.2.8/data/ellipsoid.csv failed.
    ERROR 2: CPLRealloc(): Out of memory allocating 409 bytes.
    ERROR 1: No PROJ.4 translation for source SRS, coordinate
    transformation initialization has failed.

This is with 6 threads.  The error messages change from invocation to
invocation as is typical with multi-threading bugs.

If I change the code so that one a single thread is handling the GDAL
stuff, everything works OK.

* Is this "supposed" to work?

* Do I need to do something outside the threaded portion of the code to
  initialize the projection machinery?

* If it's known not to work, what GDAL calls do I need to protect with
  locks?

Thanks for the help!

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

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