build: disable reduced exports by default

This is really a packager's option. While it's helpful to encourage devs to
test this option for daily builds, it's not reliable in several real-world
use-cases. Some older libstdc++ runtimes (freebsd 9, debian wheezy, for
example) fail to properly catch exceptions due to mismatched type_info.

See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=19664 for more info.

configure.ac

@@ -115,9 +115,9 @@ AC_ARG_ENABLE([hardening],
 
 AC_ARG_ENABLE([reduce-exports],
   [AS_HELP_STRING([--enable-reduce-exports],
-  [attempt to reduce exported symbols in the resulting executables (default is yes)])],
+  [attempt to reduce exported symbols in the resulting executables (default is no)])],
   [use_reduce_exports=$enableval],
-  [use_reduce_exports=auto])
+  [use_reduce_exports=no])
 
 AC_ARG_ENABLE([ccache],
   [AS_HELP_STRING([--enable-ccache],
@@ -473,20 +473,12 @@ AC_LINK_IFELSE([AC_LANG_SOURCE([
     if test x$use_reduce_exports = xyes; then
       AC_MSG_ERROR([Cannot find a working visibility attribute. Use --disable-reduced-exports.])
     fi
-      AC_MSG_WARN([Cannot find a working visibility attribute. Disabling reduced exports.])
-      use_reduce_exports=no
   ]
 )
 
-if test x$use_reduce_exports != xno; then
+if test x$use_reduce_exports = xyes; then
   AX_CHECK_COMPILE_FLAG([-fvisibility=hidden],[RE_CXXFLAGS="-fvisibility=hidden"],
-  [
+  [AC_MSG_ERROR([Cannot set default symbol visibility. Use --disable-reduced-exports.])])
-    if test x$use_reduce_exports = xyes; then
-      AC_MSG_ERROR([Cannot set default symbol visibility. Use --disable-reduced-exports.])
-    fi
-    AC_MSG_WARN([Cannot set default symbol visibility. Disabling reduced exports.])
-    use_reduce_exports=no
-  ])
 fi
 
 LEVELDB_CPPFLAGS=
@@ -533,7 +525,7 @@ AX_BOOST_THREAD
 AX_BOOST_CHRONO
 
 
-if test x$use_reduce_exports != xno; then
+if test x$use_reduce_exports = xyes; then
   AC_MSG_CHECKING([for working boost reduced exports])
   TEMP_CPPFLAGS="$CPPFLAGS"
   CPPFLAGS="$BOOST_CPPFLAGS $CPPFLAGS"
@@ -547,25 +539,14 @@ if test x$use_reduce_exports != xno; then
       #endif
     ]])],[
       AC_MSG_RESULT(yes)
-    ],[:
+    ],[
-    if test x$use_reduce_exports = xauto; then
+    AC_MSG_ERROR([boost versions < 1.49 are known to be broken with reduced exports. Use --disable-reduced-exports.])
-      use_reduce_exports=no
-    else
-      if test x$use_reduce_exports = xyes; then
-        AC_MSG_ERROR([boost versions < 1.49 are known to be broken with reduced exports. Use --disable-reduced-exports.])
-      fi
-    fi
-    AC_MSG_RESULT(no)
-    AC_MSG_WARN([boost versions < 1.49 are known to have symbol visibility issues. Disabling reduced exports.])
   ])
   CPPFLAGS="$TEMP_CPPFLAGS"
 fi
-
-elif test x$use_reduce_exports = xauto; then
-    use_reduce_exports=yes
 fi
 
-if test x$use_reduce_exports != xno; then
+if test x$use_reduce_exports = xyes; then
     CXXFLAGS="$CXXFLAGS $RE_CXXFLAGS"
     AX_CHECK_LINK_FLAG([[-Wl,--exclude-libs,ALL]], [RELDFLAGS="-Wl,--exclude-libs,ALL"])
 fi
@@ -827,7 +808,7 @@ else
 fi
 
 AC_MSG_CHECKING([whether to reduce exports])
-if test x$use_reduce_exports != xno; then
+if test x$use_reduce_exports = xyes; then
   AC_MSG_RESULT([yes])
 else
   AC_MSG_RESULT([no])