obs_api revision and improvements: new namespace etc. (#530)

* obs_api revision and improvements: new namespace etc.

* Minor corrections: use unused functions, add missing prototype, added fwd/invcoord to PJ

* Minor correction: MSVC barfs on va_arg type specification. Trying once more with added parens

* Reverting paren correction, which appears to be a non-solution

* Significant improvements to the OBS_API, plus a number of corrections, mostly in test code, to reflect API changes

* Added two missing prototypes

* Adding the proj_transform function and some related checks

* Improvements to proj_transform etc. based on suggestions from Even Rouault

* Reducing the libc include footprint of proj.h - again based on suggestions from Even Rouault

* A few minor corrections

* Eliminate a MSVC warning about non-initialized usage. Not an actual issue, as another check has locked the path, but at least this should calm down MSVC

* Improved support for the errno reset/restore paradigm

* Introduced the internal header proj_internal.h; Moved most non-API stuff from pj_obs_api.c to pj_internal.c

* Adding proj_internal.h to HEADERS_LIBPROJ to solve build problems

* Correcting a few pj...proj blunders in PJ_pipeline.c

* Correcting a few additional blunders in PJ_pipeline.c

* Changed angle-brackets to quotation marks in includes of proj_internal.h

* Some minor build system repairs

* Some PJ_CONTEXT usage simplifications following suggestions by Kristian Evers @kbevers

* Added version numbering to proj.h - Fixes #529

* remove proj_errno_restore macro, provide function implementation

* Add proj_get_definition. Fixes #538

* Added library specific deallocator proj_buffer_free, eliminating a potential cross heap issues on Windows. Thx to Even Rouault for spotting this

* Got rid of a meaningless cast in proj_buffer_free

* Added some missing functions to proj.def (again spotted by @rouault); removed some not-yet-implemented material from proj.h

* Renamed proj_get_definition/proj_buffer_free to proj_definition_create/proj_definition_destroy, for symmetry and clarity

* Renaming the definition handlers to proj_definition_retrieve / proj_free

* Renaming proj_free to proj_release

1 files changed, 5 insertions, 0 deletions

diff --git a/src/pj_ctx.c b/src/pj_ctx.c
index 9ae3d4e0..89b2816f 100644
--- a/src/pj_ctx.c
+++ b/src/pj_ctx.c
@@ -60,8 +60,13 @@ void pj_set_ctx( projPJ pj, projCtx ctx )
 projCtx pj_get_default_ctx()
 
 {
+    /* If already initialized, don't bother locking */
+    if( default_context_initialized )
+        return &default_context;
+
     pj_acquire_lock();
 
+    /* Ask again, since it may have been initialized in another thread */
     if( !default_context_initialized )
     {
         default_context.last_errno = 0;