Skip boost linking test if not needed

We only link against boost libraries if we do not use std::regex.
Therefore, we do not need to test how to link against boost libs unconditionally.
Also, the warning regarding stdlib-debug is only needed if we link against boost.

diff --git a/config/lyxinclude.m4 b/config/lyxinclude.m4
index 227dd93f12f16d84f833be719de4cebd3b9b4139..c1b6524ac69481c4d4ee49fe268ad7098ed94704 100644 (file)
--- a/config/lyxinclude.m4
+++ b/config/lyxinclude.m4
@@ -395,12 +395,16 @@ AC_DEFUN([LYX_USE_INCLUDED_BOOST],[
            BOOST_INCLUDES='-I$(top_srcdir)/3rdparty/boost'
            BOOST_LIBS='$(top_builddir)/3rdparty/boost/liblyxboost.a'
        else
-           AC_LANG_PUSH(C++)
-           save_LIBS=$LIBS
+           BOOST_INCLUDES=
+           if test $lyx_std_regex = yes ; then
+             BOOST_LIBS=""
+           else
+             AC_LANG_PUSH(C++)
+             save_LIBS=$LIBS
 
-           AC_MSG_CHECKING([for multithreaded boost libraries])
-           LIBS="$save_LIBS -lboost_regex-mt $LIBTHREAD"
-           AC_LINK_IFELSE(
+             AC_MSG_CHECKING([for multithreaded boost libraries])
+             LIBS="$save_LIBS -lboost_regex-mt $LIBTHREAD"
+             AC_LINK_IFELSE(
                [AC_LANG_PROGRAM([#include <boost/regex.hpp>],
                        [boost::regex reg;])],
                [AC_MSG_RESULT([yes])
@@ -416,23 +420,20 @@ AC_DEFUN([LYX_USE_INCLUDED_BOOST],[
                     [AC_MSG_RESULT([no])
                      AC_MSG_ERROR([cannot find suitable boost library (do not use --without-included-boost)])
                 ])
-           ])
-           LIBS=$save_LIBS
-           AC_LANG_POP(C++)
-           BOOST_INCLUDES=
-           if test $lyx_std_regex = yes ; then
-             BOOST_LIBS=""
-           else
-             BOOST_LIBS="-lboost_regex${BOOST_MT}"
-           fi
-
-           dnl In general, system boost libraries are incompatible with
-           dnl the use of stdlib-debug in libstdc++. See ticket #9736 for
-           dnl details.
-           if test $enable_stdlib_debug = "yes" ; then
+             ])
+             LIBS=$save_LIBS
+             AC_LANG_POP(C++)
+
+             dnl In general, system boost libraries are incompatible with
+             dnl the use of stdlib-debug in libstdc++. See ticket #9736 for
+             dnl details.
+             if test $enable_stdlib_debug = "yes" ; then
                LYX_WARNING([Compiling LyX with stdlib-debug and system boost libraries may lead to
    crashes. Consider using --disable-stdlib-debug or removing
    --without-included-boost.])
+             fi
+
+             BOOST_LIBS="-lboost_regex${BOOST_MT}"
            fi
        fi
        AC_SUBST(BOOST_INCLUDES)