Compiler flags detection in setup.py is incorrect

[Jan Blechta]

Detection of compiler flags is performed by running distutils.ccompiler.new_compiler() which is not necessarily the correct one used for actual compilation of FFC and JITing.

This is a show-stopper for some hashdist installs with custom compiler and appeared already as https://bitbucket.org/fenics-project/dolfin/issue/449 and http://fenicsproject.org/pipermail/fenics-support/2015-February/001277.html.

[Corrado Maurini]

Exporting CXXFLAGS='-std=c++11’ before running a python fenics script is an effective workaround but the issue remains valid.

[Jan Blechta]

The following patch could do the job on FFC side

diff --git a/INSTALL b/INSTALL
index df0423c..0cb5648 100644
--- a/INSTALL
+++ b/INSTALL
@@ -5,6 +5,10 @@ To install FFC, type
 This will install FFC in the default Python path of your system,
 something like /usr/lib/python2.6/site-packages/.

+To specify C++ compiler and/or compiler flags used for compiling UFC
+and JITing, set environment variables CXX, CXXFLAGS respectively
+before invoking setup.py.
+
 The installation script requires the Python module distutils, which
 for Debian users is available with the python-dev package.  Other
 dependencies are listed in the file README.
diff --git a/setup.py b/setup.py
index 9dd02e1..21bfde9 100644
--- a/setup.py
+++ b/setup.py
@@ -231,6 +231,9 @@ def run_install():

     # Check that compiler supports C++11 features
     cc = new_compiler()
+    CXX = os.environ.get("CXX")
+    if CXX:
+        cc.set_executables(compiler_so=CXX)
     CXX_FLAGS = os.environ.get("CXXFLAGS", "")
     if has_cxx_flag(cc, "-std=c++11"):
         CXX_FLAGS += " -std=c++11"

@johannes_ring, could you try it?

Note the tricky thing in distutils/unixccompiler.py:_compile, it uses compiler_so, not compiler nor compiler_cxx.

The rest would be to export CXX on hashdist side.

[Jan Blechta]

@johannes_ring, any progress here?

[Sean Farley]

Just to chime in from MacPorts but this was a surprising (perhaps more surprising that this isn't automatically solved within distutils) bug.

[Johannes Ring]

Thanks @blechta, this looks good to me. Can you make a pull request?

[Jan Blechta]

@johannes_ring Ok. Can I have write access to FFC repo so that we don't have to deal with other repo?

[Johannes Ring]

Yes @blechta, I assume that is fine since you already have write access to the DOLFIN repository. I have given you write access to the FFC repository now.

[Johannes Ring]

Fixed in d7523e79bddb4544526570207e55dff5ac109505.

[Martin Sandve Alnæs]

Removing milestone: 1.6 (automated comment)