Control symbol exports using -fvisibility

On systems using GCC 4.0 or newer which support symbol visibility in shared
libraries, use -fvisibility=hidden and only export explict API functions
defined in zmq.cpp. We do not enable -fvisibility on MinGW since this uses a
separate mechanism (__declspec).
Signed-off-by: Martin Lucina <mato@kotelna.sk>

configure.in

@@ -223,6 +223,18 @@ case "${host_os}" in
         ;;
 esac
 
+# Check if the compiler supports -fvisibility=hidden. If so, use it, but not
+# on MinGW32 where we use a separate mechanism (__declspec).
+_LT_COMPILER_OPTION([if $compiler supports -fvisibility=hidden],
+                    ac_cv_prog_compiler_visibility,
+                    [-fvisibility=hidden],
+                    [],
+                    [have_dso_visibility=yes])
+if test "x$have_dso_visibility" = "xyes" -a "x$on_mingw32" = "xno"; then
+    LIBZMQ_EXTRA_CFLAGS="-fvisibility=hidden $LIBZMQ_EXTRA_CFLAGS"
+    LIBZMQ_EXTRA_CXXFLAGS="-fvisibility=hidden $LIBZMQ_EXTRA_CXXFLAGS"
+fi
+
 # CPU-specific optimizations
 case "${host_cpu}" in
     *sparc*)

include/zmq.h

@@ -39,6 +39,9 @@ extern "C" {
 #   endif
 #else
 #   define ZMQ_EXPORT
+#   if defined __GNUC__ && __GNUC__ >= 4
+#       pragma GCC visibility push(default)
+#   endif
 #endif
 
 /******************************************************************************/
@@ -242,6 +245,11 @@ ZMQ_EXPORT int zmq_poll (zmq_pollitem_t *items, int nitems, long timeout);
 
 ZMQ_EXPORT int zmq_device (int device, void * insocket, void* outsocket);
 
+#undef ZMQ_EXPORT
+#if defined __GNUC__ && __GNUC__ >= 4 && !defined _WIN32
+#    pragma GCC visibility pop
+#endif
+
 #ifdef __cplusplus
 }
 #endif

include/zmq_utils.h

@@ -33,6 +33,9 @@ extern "C" {
 #   endif
 #else
 #   define ZMQ_EXPORT
+#   if defined __GNUC__ && __GNUC__ >= 4
+#       pragma GCC visibility push(default)
+#   endif
 #endif
 
 /*  Helper functions are used by perf tests so that they don't have to care   */
@@ -49,6 +52,9 @@ ZMQ_EXPORT unsigned long zmq_stopwatch_stop (void *watch_);
 ZMQ_EXPORT void zmq_sleep (int seconds_);
 
 #undef ZMQ_EXPORT
+#if defined __GNUC__ && __GNUC__ >= 4 && !defined _WIN32
+#    pragma GCC visibility pop
+#endif
 
 #ifdef __cplusplus
 }

src/Makefile.am

@@ -203,7 +203,6 @@ libpgm_diff_flags = \
     -DCONFIG_HAVE_ISO_VARARGS \
     -DCONFIG_HAVE_TSC \
     -DCONFIG_HAVE_WSACMSGHDR \
-    -DCONFIG_HAVE_DSO_VISIBILITY \
     -DCONFIG_BIND_INADDR_ANY
 
 else
@@ -225,7 +224,6 @@ libpgm_diff_flags = \
     -DCONFIG_HAVE_IP_MREQN \
     -DCONFIG_HAVE_SPRINTF_GROUPING \
     -DCONFIG_HAVE_VASPRINTF \
-    -DCONFIG_HAVE_DSO_VISIBILITY \
     -DCONFIG_BIND_INADDR_ANY \
     -DCONFIG_HAVE_GETOPT
 endif
@@ -237,6 +235,7 @@ libpgm_la_CFLAGS = -I$(top_srcdir)/foreign/openpgm/@pgm_basename@/openpgm/pgm/in
     -DCONFIG_16BIT_CHECKSUM \
     -DCONFIG_GALOIS_MUL_LUT \
     -DGETTEXT_PACKAGE='"pgm"' \
+    -DPGM_GNUC_INTERNAL= \
     ${libpgm_diff_flags}
 
 libzmq_la_CXXFLAGS = -I$(top_srcdir)/foreign/openpgm/@pgm_basename@/openpgm/pgm/include/ \

src/zmq.cpp

@@ -60,6 +60,10 @@
 #include <pgm/pgm.h>
 #endif
 
+#if defined __GNUC__ && __GNUC__ >= 4 && !defined ZMQ_HAVE_WINDOWS
+#pragma GCC visibility push(default)
+#endif
+
 void zmq_version (int *major_, int *minor_, int *patch_)
 {
     *major_ = ZMQ_VERSION_MAJOR;
@@ -725,3 +729,7 @@ unsigned long zmq_stopwatch_stop (void *watch_)
     return (unsigned long) (end - start);
 }
 
+#if defined __GNUC__ && __GNUC__ >= 4 && !defined ZMQ_HAVE_WINDOWS
+#pragma GCC visibility pop
+#endif
+