Strangely for my development build, the build system appears convinced that it is using clang 6.1.0... Editing around line 784 of libtbx/SConscript, where clang_version is determined, to read: from subprocess import call print call(["which", "clang"]) print call(["clang", "--version"]) flag, output = conf.TryRun("\n".join(test_code), extension='.cpp') conf.Finish() assert flag output = output.replace(":,", ":None,") print output I get the following output: /usr/bin/clang 0 Apple LLVM version 7.3.0 (clang-703.0.29) Target: x86_64-apple-darwin15.3.0 Thread model: posix InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin 0 {"llvm":1, "clang":1, "clang_major":6, "clang_minor":1, "clang_patchlevel":0, "GNUC":4, "GNUC_MINOR":2, "GNUC_PATCHLEVEL":1, "clang_version": "6.1.0 (clang-602.0.53)", "VERSION": "4.2.1 Compatible Apple LLVM 6.1.0 (clang-602.0.53)", } On MacOS, using clang 6.1.0 If I wipe the build directory (or rather, renamed so not wiped completely) then it is now happy that it is using clang 7.3.0: /usr/bin/clang 0 Apple LLVM version 7.3.0 (clang-703.0.29) Target: x86_64-apple-darwin15.3.0 Thread model: posix InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin 0 {"llvm":1, "clang":1, "clang_major":7, "clang_minor":3, "clang_patchlevel":0, "GNUC":4, "GNUC_MINOR":2, "GNUC_PATCHLEVEL":1, "clang_version": "7.3.0 (clang-703.0.29)", "VERSION": "4.2.1 Compatible Apple LLVM 7.3.0 (clang-703.0.29)", } On MacOS, using clang 7.3.0 Any idea what is going on here? Why does it think it is somehow using an older version of the clang to what is actually installed?! Cheers, Richard Dr Richard Gildea Data Analysis Scientist Tel: +441235 77 8078 Diamond Light Source Ltd. Diamond House Harwell Science & Innovation Campus Didcot Oxfordshire OX11 0DE ________________________________ From: [email protected] [[email protected]] on behalf of Luc Bourhis [[email protected]] Sent: 07 April 2016 10:23 To: cctbx mailing list Subject: Re: [cctbxbb] Boost broken on mac? Could you confirm whether the following two tests fail for you after your latest change? libtbx.python "/Users/rjgildea/tmp/tst_bootstrap/tmp/modules/cctbx_project/cctbx/maptbx/boost_python/tst_maptbx.py" [FAIL] […] libtbx.python "/Users/rjgildea/tmp/tst_bootstrap/tmp/modules/cctbx_project/scitbx/lbfgs/tst_lbfgs_fem.py" [FAIL] […] I see those too. Tracking them is too much effort indeed. I followed the route already suggested by Marcin: break -ffast-math in finer options and find the one breaking our code. After a round-trip through Clang source code (I wish they had a proper documentation of *all* their command-line options as it exists for gcc), I came with a fix which keeps all useful optimisations enabled while the 3 failing tests do now pass. Gonna commit shortly. Best wishes, Luc -- This e-mail and any attachments may contain confidential, copyright and or privileged material, and are for the use of the intended addressee only. If you are not the intended addressee or an authorised recipient of the addressee please notify us of receipt by returning the e-mail and do not use, copy, retain, distribute or disclose the information in or attached to the e-mail. Any opinions expressed within this e-mail are those of the individual and not necessarily of Diamond Light Source Ltd. Diamond Light Source Ltd. cannot guarantee that this e-mail or any attachments are free from viruses and we cannot accept liability for any damage which you may sustain as a result of software viruses which may be transmitted in or with the message. Diamond Light Source Limited (company no. 4375679). Registered in England and Wales with its registered office at Diamond House, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0DE, United Kingdom