From 9a23a23ef20f6f5bd10e5dd4b16fa6c03ba40895 Mon Sep 17 00:00:00 2001
From: Even Rouault <even.rouault@spatialys.com>
Date: Tue, 12 Nov 2019 13:33:47 +0100
Subject: [PATCH] Fix proj_assign_context()/pj_set_ctx() with pipelines and
 alternative coord operations

Fixes https://github.com/OSGeo/gdal/issues/1989

pj_set_ctx() only changes the context to the main object. It should also
recurse down to the steps of the pipeline and the alternative coordinate
operations hold in alternativeCoordinateOperations

In the GDAL use case with multithreaded reprojection, and objects being transferred
between thread, this would cause a failed coordinate transformation to affect
an unrelated transformation of another thread...
---
 src/ctx.cpp         | 8 ++++++++
 src/pipeline.cpp    | 6 +++++-
 src/proj_internal.h | 2 ++
 3 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/ctx.cpp b/src/ctx.cpp
index 622a814d9f..bcb6e1ccfb 100644
--- a/src/ctx.cpp
+++ b/src/ctx.cpp
@@ -60,6 +60,14 @@ void pj_set_ctx( projPJ pj, projCtx ctx )
     if (pj==nullptr)
         return;
     pj->ctx = ctx;
+    if( pj->is_pipeline )
+    {
+        pj_pipeline_assign_context_to_steps(pj, ctx);
+    }
+    for( const auto &alt: pj->alternativeCoordinateOperations )
+    {
+        pj_set_ctx(alt.pj, ctx);
+    }
 }
 
 /************************************************************************/
diff --git a/src/pipeline.cpp b/src/pipeline.cpp
index a82fce312b..847f819495 100644
--- a/src/pipeline.cpp
+++ b/src/pipeline.cpp
@@ -136,7 +136,11 @@ static PJ_LPZ    pipeline_reverse_3d (PJ_XYZ xyz, PJ *P);
 static PJ_XY     pipeline_forward (PJ_LP lp, PJ *P);
 static PJ_LP     pipeline_reverse (PJ_XY xy, PJ *P);
 
-
+void pj_pipeline_assign_context_to_steps( PJ* P, PJ_CONTEXT* ctx )
+{
+    for (int i = 1; i <= static_cast<struct pj_opaque*>(P->opaque)->steps; i++)
+        proj_assign_context(static_cast<struct pj_opaque*>(P->opaque)->pipeline[i], ctx);
+}
 
 
 static PJ_COORD pipeline_forward_4d (PJ_COORD point, PJ *P) {
diff --git a/src/proj_internal.h b/src/proj_internal.h
index 6d978b35cc..5289e1c99e 100644
--- a/src/proj_internal.h
+++ b/src/proj_internal.h
@@ -922,6 +922,8 @@ std::string pj_double_quote_string_param_if_needed(const std::string& str);
 PJ *pj_create_internal (PJ_CONTEXT *ctx, const char *definition);
 PJ *pj_create_argv_internal (PJ_CONTEXT *ctx, int argc, char **argv);
 
+void pj_pipeline_assign_context_to_steps( PJ* P, PJ_CONTEXT* ctx );
+
 /* classic public API */
 #include "proj_api.h"