Enabled plug-in loading on all hosts with support for dlopen()

Previously the code used for loading plug-ins would be built only on
Linux hosts. Now the required functions are checked for and plug-in
loading code is enabled if those are present on all platforms. Using
lstat() to check for file types also increases portability to hosts that
do not have the dirent.d_type field. If shared libraries support is
disabled plug-ins will also be automatically disabled.

Signed-off-by: Gabriele Svelto <gabriele.svelto@gmail.com>

3 files changed, 69 insertions, 19 deletions

diff --git a/configure.ac b/configure.ac
index 339cc37..50b4457 100644
--- a/configure.ac
+++ b/configure.ac
@@ -99,8 +99,6 @@ AS_CASE(["${host_os}"],
                 AC_DEFINE([XS_HAVE_ANDROID], [1], [Have Android OS])
             ]
         )
-
-        AC_CHECK_LIB([dl], [dlopen])
      ],
     [*solaris*], [
         AC_DEFINE([XS_HAVE_SOLARIS], [1], [Have Solaris OS])
@@ -191,7 +189,11 @@ LIBXS_CHECK_DOC_BUILD
 # Checks for header files.
 AC_HEADER_STDC
 AC_CHECK_HEADERS([ \
+    link.h \
+    dirent.h \
+    dlfcn.h \
     errno.h \
+    fcntl.h \
     arpa/inet.h \
     netinet/tcp.h \
     netinet/in.h \
@@ -199,6 +201,7 @@ AC_CHECK_HEADERS([ \
     stdlib.h \
     string.h \
     sys/socket.h \
+    sys/stat.h \
     sys/time.h \
     sys/types.h \
     time.h \
@@ -374,6 +377,34 @@ AS_IF([test "x$enable_libzmq" != "xno"], [
     libxs_libzmq="yes"
 ])
 
+# Plug-in support
+AC_ARG_ENABLE([plugins], [AS_HELP_STRING([--enable-plugins],
+    [enable plugins [default=auto]])],
+    [enable_plugins=$enableval], [enable_plugins=auto])
+
+AS_IF([test "x$enable_plugins" != "xno"], [
+    # Check if libdl is required, then check for dlopen and lstat, they are
+    # both needed to enable plug-in support
+    AC_SEARCH_LIBS([dlopen], [dl])
+    AC_CHECK_FUNCS([lstat dlopen], [], [
+        AS_IF([test "x$enable_plugins" = "xyes"], [
+            AC_MSG_ERROR([Plugins support not available])
+        ], [
+            AC_MSG_WARN([Plugins support disabled])
+            enable_plugins=no
+        ])
+    ])
+
+    # If shared library support is disabled disable plugins support
+    AS_IF([test "x$enable_shared" = "xno"], [
+        AC_MSG_WARN([Shared library support disabled, disabling plug-ins])
+        enable_plugins=no
+    ], [
+        enable_plugins=yes
+        AC_DEFINE([XS_HAVE_PLUGINS], [1], [Whether plugins support is enabled])
+    ])
+])
+
 #  PGM extension
 libxs_pgm_ext="no"
 
@@ -525,6 +556,7 @@ Configuration for $PACKAGE_STRING
     Polling system: $libxs_cv_poller
     Disable eventfd: $xs_disable_eventfd
     Build libzmq compatibility library and headers: $libxs_libzmq
+    Plugins support: $enable_plugins
     PGM extension: $with_pgm_ext
     Use system-provided PGM library: $with_system_pgm_ext
     Build documentation: $libxs_build_doc
diff --git a/src/ctx.cpp b/src/ctx.cpp
index f5d9719..063f96c 100644
--- a/src/ctx.cpp
+++ b/src/ctx.cpp
@@ -23,12 +23,27 @@
 #if defined XS_HAVE_WINDOWS
 #include "windows.hpp"
 #else
-#include <unistd.h>
-#endif
-
-#if defined XS_HAVE_LINUX
-#include <dlfcn.h>
-#include <dirent.h>
+#   if HAVE_UNISTD_H
+#       include <unistd.h>
+#   endif
+#   if HAVE_SYS_TYPES_H
+#       include <sys/types.h>
+#   endif
+#   if HAVE_SYS_STAT_H
+#       include <sys/stat.h>
+#   endif
+#   if HAVE_DLFCN_H
+#       include <dlfcn.h>
+#   endif
+#   if HAVE_LINK_H
+#       include <link.h>
+#   endif
+#   if HAVE_FCNTL_H
+#       include <fcntl.h>
+#   endif
+#   if HAVE_DIRENT_H
+#       include <dirent.h>
+#   endif
 #endif
 
 #include <new>
@@ -114,7 +129,7 @@ next:
     BOOL brc = FindClose (fh);
     win_assert (brc != 0);
 
-#elif defined XS_HAVE_LINUX
+#elif XS_HAVE_PLUGINS
 
     //  Load all the installed plug-ins.
     std::string path (XS_PREFIX_PATH);
@@ -126,12 +141,17 @@ next:
     errno_assert (dp);
 
     dirent dir, *dirp;
+    struct stat stats;
+
     while (true) {
         rc = readdir_r (dp, &dir, &dirp);
         assert (rc == 0);
         if (!dirp)
             break;
-        if (dir.d_type == DT_REG) {
+
+        rc = lstat (dirp->d_name, &stats);
+
+        if ((rc == 0) && S_ISREG (stats.st_mode)) {
 
             //  Ignore the files without .xsp extension.
             std::string file = dir.d_name;
@@ -139,7 +159,7 @@ next:
                 continue;
             if (file.substr (file.size () - 4) != ".xsp")
                 continue;
-            
+
             //  Open the specified dynamic library.
             std::string filename = path + "/" + file;
             void *dl = dlopen (filename.c_str (), RTLD_LOCAL | RTLD_NOW);
@@ -260,7 +280,7 @@ int xs::ctx_t::terminate ()
           it != plugins.end (); ++it)
         FreeLibrary (*it);
     opt_sync.unlock ();
-#elif defined XS_HAVE_LINUX
+#elif XS_HAVE_PLUGINS
     opt_sync.lock ();
     for (plugins_t::iterator it = plugins.begin ();
           it != plugins.end (); ++it)
@@ -412,7 +432,7 @@ void xs::ctx_t::destroy_socket (class socket_base_t *socket_)
     //  Free the associared thread slot.
     uint32_t tid = socket_->get_tid ();
     empty_slots.push_back (tid);
-    slots [tid] = NULL;    
+    slots [tid] = NULL;
 
     //  Remove the socket from the list of sockets.
     sockets.erase (socket_);
@@ -497,7 +517,7 @@ void xs::ctx_t::unregister_endpoints (socket_base_t *socket_)
         }
         ++it;
     }
-        
+
     endpoints_sync.unlock ();
 }
 
@@ -528,4 +548,3 @@ xs::endpoint_t xs::ctx_t::find_endpoint (const char *addr_)
 //  is a global variable. Thus, even sockets created in different contexts have
 //  unique IDs.
 xs::atomic_counter_t xs::ctx_t::max_socket_id;
-
diff --git a/src/ctx.hpp b/src/ctx.hpp
index 7b0b74b..8e2fd03 100644
--- a/src/ctx.hpp
+++ b/src/ctx.hpp
@@ -54,7 +54,7 @@ namespace xs
 
     //  Context object encapsulates all the global state associated with
     //  the library.
-    
+
     class ctx_t
     {
     public:
@@ -173,7 +173,7 @@ namespace xs
 #if defined XS_HAVE_WINDOWS
         typedef std::vector <HMODULE> plugins_t;
         plugins_t plugins;
-#elif defined XS_HAVE_LINUX
+#elif defined XS_HAVE_PLUGINS
         typedef std::vector <void*> plugins_t;
         plugins_t plugins;
 #endif
@@ -185,8 +185,7 @@ namespace xs
         ctx_t (const ctx_t&);
         const ctx_t &operator = (const ctx_t&);
     };
-    
+
 }
 
 #endif
-