[buddy] Probe for -fvisibility and -fvisibility-inlines-hidden.

* configure.ac: Check gcc and g++ for -fvisibility and
-fvisibility-inlines-hidden.  Add these options to
CFLAGS and CXXFLAGS.
* m4/ax_check_compile_flag.m4: New file.
* src/Makefile.am: Build BuDDy as a single library, reverting part of
the changes introduced in my previous patch to this file.  Since
the options are set in CFLAGS/CXXFLAGS, there is no possibility
for -fvisibility-inlines-hidden to be passed to the C compiler.

buddy/configure.ac

@@ -20,6 +20,18 @@ AC_PROG_CXX
 
 LT_INIT([win32-dll])
 
+# Use -Werror since using -fvisibility under MinGW is only a warning.
+# (The option is ignored anyway since this does not make sense under windows).
+AX_CHECK_COMPILE_FLAG([-Werror -fvisibility=hidden],
+  [CFLAGS="$CFLAGS -fvisibility=hidden"])
+AC_LANG(C++)
+AX_CHECK_COMPILE_FLAG([-Werror -fvisibility=hidden],
+  [CXXFLAGS="$CXXFLAGS -fvisibility=hidden"
+  AX_CHECK_COMPILE_FLAG([-fvisibility-inlines-hidden],
+    [CXXFLAGS="$CXXFLAGS -fvisibility-inlines-hidden"])])
+AC_LANG(C)
+
+
 adl_ENABLE_DEBUG
 ad_GCC_OPTIM
 adl_NDEBUG
@@ -31,6 +43,7 @@ if test x$enable_warnings = xyes; then
   CF_GCC_WARNINGS
 fi
 
+
 AC_CONFIG_HEADERS([config.h])
 
 AC_CONFIG_FILES([

buddy/m4/ax_check_compile_flag.m4

@@ -0,0 +1 @@
+../../m4/ax_check_compile_flag.m4

buddy/src/Makefile.am

@@ -1,29 +1,21 @@
 
 include_HEADERS = bdd.h fdd.h bvec.h
 
-BUDDY_FLAGS = -I$(top_builddir) -DVERSION=23 \
-  -fvisibility=hidden -DBUDDY_DLL_EXPORTS -DBUDDY_DLL
+BUDDY_FLAGS = -I$(top_builddir) -DVERSION=23 -DBUDDY_DLL_EXPORTS -DBUDDY_DLL
 
-# Compile the C++ part of the library with
-# -fvisibility-inlines-hidden, this option is not valid for C.
 lib_LTLIBRARIES = libbdd.la
-libbdd_la_CPPFLAGS = $(BUDDY_FLAGS) -fvisibility-inlines-hidden
-libbdd_la_SOURCES = cppext.cxx
-libbdd_la_LIBADD = libbdd_c.la
 # See the `Updating version info' node of the Libtool manual before
 # changing this.
 libbdd_la_LDFLAGS = -no-undefined -version-info 0:0:0
-
-# The C part of the library.
-noinst_LTLIBRARIES = libbdd_c.la
-libbdd_c_la_CPPFLAGS = $(BUDDY_FLAGS)
-libbdd_c_la_SOURCES = \
+libbdd_la_CPPFLAGS = $(BUDDY_FLAGS)
+libbdd_la_SOURCES = \
  bddio.c \
  bddop.c \
  bddtree.h \
  bvec.c \
  cache.c \
  cache.h \
+ cppext.cxx \
  fdd.c \
  imatrix.c \
  imatrix.h \