Repository: spack/spack

Issue:
expat@2.2.2 fails to build w/out high quality source of randomness
@adamjstewart updated expat to 2.2.2 yesterday.  One of the changes is 

> Protect against compilation without any source of high
>        quality entropy enabled, e.g. with CMake build system;
> from https://github.com/libexpat/libexpat/blob/R_2_2_2/expat/Changes

High quality source of randomness appear to be the getrandom() call (linux 3.17+) the SYS_getrandom system call (linux 3.17+) or arc4random_buf (bsd or libbsd).

I apparently have none of the above (CentOS 7 kernel running `3.10.0-327.36.3.el7.x86_64`).

I'm not entirely sure what people in my situation (older kernels) are supposed to do.  

One solution might be to add a package for [libbsd](https://libbsd.freedesktop.org/wiki/).

It seems like [sjackman ran into the same problem](https://github.com/libexpat/libexpat/issues/88) with Ubuntu 14.04.  His solution was to depend on `libbsd`.

Alternatively, we could add a variant that defines `XML_POOR_ENTROPY`.

I'll look into `libbsd`.




Discussion:

Resolving patch:
diff --git a/var/spack/repos/builtin/packages/expat/package.py b/var/spack/repos/builtin/packages/expat/package.py
--- a/var/spack/repos/builtin/packages/expat/package.py
+++ b/var/spack/repos/builtin/packages/expat/package.py
@@ -31,5 +31,24 @@ class Expat(AutotoolsPackage):
     homepage = "http://expat.sourceforge.net/"
     url      = "https://sourceforge.net/projects/expat/files/expat/2.2.2/expat-2.2.2.tar.bz2"
 
+    # Version 2.2.2 introduced a requirement for a high quality
+    # entropy source.  "Older" linux systems (aka CentOS 7) do not
+    # support get_random so we'll provide a high quality source via
+    # libbsd.
+    # There's no need for it in earlier versions, so 'conflict' if
+    # someone's asking for an older version and also libbsd.
+    # In order to install an older version, you'll need to add
+    # `~libbsd`.
+    variant('libbsd', default=True,
+            description="Use libbsd (for high quality randomness)")
+    depends_on('libbsd', when="@2.2.1:+libbsd")
+
     version('2.2.2', '1ede9a41223c78528b8c5d23e69a2667')
     version('2.2.0', '2f47841c829facb346eb6e3fab5212e2')
+
+    def configure_args(self):
+        spec = self.spec
+        args = []
+        if '+libbsd' in spec and '@2.2.1:' in spec:
+            args = ['--with-libbsd']
+        return args
diff --git a/var/spack/repos/builtin/packages/libbsd/package.py b/var/spack/repos/builtin/packages/libbsd/package.py
new file mode 100644
--- /dev/null
+++ b/var/spack/repos/builtin/packages/libbsd/package.py
@@ -0,0 +1,38 @@
+##############################################################################
+# Copyright (c) 2013-2016, Lawrence Livermore National Security, LLC.
+# Produced at the Lawrence Livermore National Laboratory.
+#
+# This file is part of Spack.
+# Created by Todd Gamblin, tgamblin@llnl.gov, All rights reserved.
+# LLNL-CODE-647188
+#
+# For details, see https://github.com/llnl/spack
+# Please also see the NOTICE and LICENSE files for our notice and the LGPL.
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU Lesser General Public License (as
+# published by the Free Software Foundation) version 2.1, February 1999.
+#
+# This program is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the IMPLIED WARRANTY OF
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the terms and
+# conditions of the GNU Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this program; if not, write to the Free Software
+# Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+##############################################################################
+from spack import *
+
+
+class Libbsd(AutotoolsPackage):
+    """This library provides useful functions commonly found on BSD
+    systems, and lacking on others like GNU systems, thus making it easier
+    to port projects with strong BSD origins, without needing to embed the
+    same code over and over again on each project.
+    """
+
+    homepage = "https://libbsd.freedesktop.org/wiki/"
+    url      = "https://libbsd.freedesktop.org/releases/libbsd-0.8.6.tar.xz"
+
+    version('0.8.6', '4ab7bec639af17d0aacb50222b479110')


Test patch: