[commit: ghc] master: Verify minimum required version of sphinx-build (7dae074)

[git at git.haskell.org]

Repository : ssh://git@git.haskell.org/ghc

On branch  : master
Link       : http://ghc.haskell.org/trac/ghc/changeset/7dae0743c8162021fa4d11c33c89b43e3e568991/ghc

>---------------------------------------------------------------

commit 7dae0743c8162021fa4d11c33c89b43e3e568991
Author: Ben Gamari <ben at smart-cactus.org>
Date:   Fri Oct 23 12:27:35 2015 +0200

    Verify minimum required version of sphinx-build
    
    CentOS 6.6 includes sphinx-build 0.6.6 which is woefully inadequate to
    build the users guide. In particular it fails as it lacks
    `sphinx.ext.extlinks`, which was introduced in 1.0.0. Looking at the
    changelog it appears that 1.0.0 ought to work.


>---------------------------------------------------------------

7dae0743c8162021fa4d11c33c89b43e3e568991
 configure.ac | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/configure.ac b/configure.ac
index 6b01076..925846a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -772,6 +772,15 @@ fi
 
 dnl ** check for Sphinx toolchain
 AC_PATH_PROG(SPHINXBUILD,sphinx-build)
+AC_CACHE_CHECK([for version of sphinx-build], sphinx_version,
+changequote(, )dnl
+[if test -n "$SPHINXBUILD"; then
+  sphinx_version=`"$SPHINXBUILD" --version | sed 's/Sphinx (sphinx-build) \([0-9]\.[0-9]\.[0-9]\)/\1/'`;
+fi;
+changequote([, ])dnl
+])
+FP_COMPARE_VERSIONS([$sphinx_version],-lt,1.0.0,
+    [AC_MSG_ERROR([Sphinx version 1.0.0 or later is required to build documentation]); SPHINXBUILD=;])
 
 dnl ** check for xelatex
 AC_PATH_PROG(XELATEX,xelatex)