win32: Don't use dllexport/import when only building statically

If the prototypes in the public API have dllimport in them when building
statically on Windows, the compiler will look for symbols with symbol
mangling and indirection corresponding to a DLL. This will cause a build
failure when trying to link tests/examples/etc.

External users of GStreamer also need to define -DGST_STATIC_COMPILATION
if they want to link to static gstreamer libraries on Windows.

A similar version of this patch has been committed to all gstreamer
repositories.

https://bugzilla.gnome.org/show_bug.cgi?id=767463

diff --git a/configure.ac b/configure.ac
index d40d33a..6aa06e3 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -188,6 +188,12 @@ fi
 AC_SUBST(GST_PLUGIN_LIBTOOLFLAGS)
 AM_CONDITIONAL(GST_PLUGIN_BUILD_STATIC, test "x$enable_static_plugins" = "xyes")
 
+dnl If only building static libraries, define GST_STATIC_COMPILATION. This is
+dnl needed only on Windows, but it doesn't hurt to have it everywhere.
+if test x$enable_static = xyes -a x$enable_shared = xno; then
+  GST_OBJ_STATIC_CFLAGS="-DGST_STATIC_COMPILATION"
+fi
+
 dnl building of tests
 AC_ARG_ENABLE(tests,
   AS_HELP_STRING([--disable-tests],[disable building test apps]),
@@ -950,8 +956,8 @@ AC_SUBST(GST_LIB_LDFLAGS)
 dnl GST_OBJ_*
 dnl default vars for all internal objects built on libgstreamer
 dnl includes GST_ALL_*
-GST_OBJ_CFLAGS="\$(GST_ALL_CFLAGS)"
-GST_OBJ_CXXFLAGS="\$(GST_ALL_CXXFLAGS)"
+GST_OBJ_CFLAGS="\$(GST_ALL_CFLAGS) $GST_OBJ_STATIC_CFLAGS"
+GST_OBJ_CXXFLAGS="\$(GST_ALL_CXXFLAGS) $GST_OBJ_STATIC_CFLAGS"
 GST_OBJ_LIBS="\$(top_builddir)/gst/libgstreamer-$GST_API_VERSION.la \$(GST_ALL_LIBS)"
 AC_SUBST(GST_OBJ_CFLAGS)
 AC_SUBST(GST_OBJ_CXXFLAGS)

diff --git a/gst/gstconfig.h.in b/gst/gstconfig.h.in
index 41f76b6..8a951fb 100644 (file)
--- a/gst/gstconfig.h.in
+++ b/gst/gstconfig.h.in
@@ -133,7 +133,13 @@
  * On Windows, this exports the plugin definition from the DLL.
  * On other platforms, this gets defined as a no-op.
  */
-#ifdef _WIN32 /* Both 32-bit and 64-bit; both GCC and MSVC */
+/* Macro _WIN32 is defined on 32-bit and 64-bit Windows; by both GCC and MSVC
+ *
+ * NOTE: To link to Windows statically on Windows, you must define
+ * GST_STATIC_COMPILATION or the prototypes will cause the compiler to search
+ * for the symbol inside a DLL
+ */
+#if defined(_WIN32) && !defined(GST_STATIC_COMPILATION)
 # define GST_PLUGIN_EXPORT __declspec(dllexport) extern
 # ifdef GST_EXPORTS
 #  define GST_EXPORT __declspec(dllexport) extern