From e896ae1c43376b5fc576061ece1dbac79146d236 Mon Sep 17 00:00:00 2001
From: Matthew Broadway <matthew.broadway@navenio.com>
Date: Wed, 30 Jan 2019 09:41:28 +0000
Subject: [PATCH] compile cython compatible with the chosen python version

---
 cmake/GtsamCythonWrap.cmake | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/cmake/GtsamCythonWrap.cmake b/cmake/GtsamCythonWrap.cmake
index 73e2b63e0..520d72a32 100644
--- a/cmake/GtsamCythonWrap.cmake
+++ b/cmake/GtsamCythonWrap.cmake
@@ -35,6 +35,11 @@ function(set_up_required_cython_packages)
   include_directories(${NUMPY_INCLUDE_DIRS})
 endfunction()
 
+execute_process(COMMAND "${PYTHON_EXECUTABLE}" "-c"
+    "from __future__ import print_function;import sys;print(sys.version[0], end='')"
+    OUTPUT_VARIABLE PYTHON_MAJOR_VERSION
+)
+
 # Convert pyx to cpp by executing cython
 # This is the first step to compile cython from the command line
 # as described at: http://cython.readthedocs.io/en/latest/src/reference/compilation.html
@@ -52,7 +57,7 @@ function(pyx_to_cpp target pyx_file generated_cpp include_dirs)
   add_custom_command(
     OUTPUT ${generated_cpp}
     COMMAND
-      ${CYTHON_EXECUTABLE} -X boundscheck=False -v --fast-fail --cplus ${includes_for_cython} ${pyx_file} -o ${generated_cpp}
+    ${CYTHON_EXECUTABLE} -X boundscheck=False -v --fast-fail --cplus -${PYTHON_MAJOR_VERSION} ${includes_for_cython} ${pyx_file} -o ${generated_cpp}
     VERBATIM)
   add_custom_target(${target} ALL DEPENDS ${generated_cpp})
 endfunction()