Re: [gst-devel] Undefined symbols

[David S. <ds...@sc...>]

On Mon, Apr 05, 2004 at 10:37:32PM +0200, Julio M. Merino Vidal wrote:
> So, if I understood it correctly, here is what's going on when I do
> 'gst-inspect esdsink':
> 
> 1) gst-inspect finds and opens the esdsink plugin, which is the libgstesd.so
>    shared file.
> 2) It searches for the plugin_init function and calls it.

Actually, it looks for gst_plugin_desc, which is a structure that
almost always contains a pointer to a function called plugin_init,
for historical reasons.

> 3) plugin_init from libgstesd.so does a gst_library_load to load the
>    libgstaudio.so plugin, so that it can later call its functions.
> 4) esdsink calls a function from libgstaudio, and should work because the
>    library has been loaded.  But instead, it fails.
> 
> Am I right?

Yes.

> If so, I've prepared a simple testcase that tries to simulate
> this behavior (w/o using any of the gst/glib code, just plain calls to
> dlopen and other functions).  You can find it here (less than 1kb):
> 
> 	ftp://ftp.NetBSD.org/pub/NetBSD/misc/jmmv/plugins-tc.tar.gz
> 
> This fails under NetBSD, as seen below:

It also fails under Linux.  Patch below.  I'm not entirely certain
how to interpret the POSIX spec in this case.

(Have I mentioned that I really dislike dlopen()?)



dave...


diff -u plugins-tc/Makefile plugins-tc-ds/Makefile
--- plugins-tc/Makefile	2004-04-05 13:25:52.000000000 -0700
+++ plugins-tc-ds/Makefile	2004-04-05 14:15:32.000000000 -0700
@@ -1,7 +1,7 @@
 all: main plugin1.so plugin2.so
 
 main: main.c
-	cc -o main main.c
+	cc -o main main.c -ldl
 
 plugin1.so: plugin1.c
 	cc -shared -Wl,--export-dynamic -fPIC -DPIC -o plugin1.so plugin1.c -ldl
diff -u plugins-tc/main.c plugins-tc-ds/main.c
--- plugins-tc/main.c	2004-04-05 13:25:40.000000000 -0700
+++ plugins-tc-ds/main.c	2004-04-05 14:15:12.000000000 -0700
@@ -2,7 +2,7 @@
 #include <stdio.h>
 
 #if defined(__NetBSD__)
-#define RTDL_LAZY DL_LAZY
+#define RTLD_LAZY DL_LAZY
 #endif
 
 int
@@ -12,7 +12,7 @@
 	void (*plugin_init)(void);
 	void (*plugin_func)(void);
 
-	if ((handle = dlopen("./plugin1.so", RTDL_LAZY)) == NULL)
+	if ((handle = dlopen("./plugin1.so", RTLD_LAZY)) == NULL)
 		dlerror();
 
 	plugin_init = dlsym(handle, "plugin1_init");
diff -u plugins-tc/plugin1.c plugins-tc-ds/plugin1.c
--- plugins-tc/plugin1.c	2004-04-05 13:25:34.000000000 -0700
+++ plugins-tc-ds/plugin1.c	2004-04-05 14:16:48.000000000 -0700
@@ -2,13 +2,13 @@
 #include <stdio.h>
 
 #if defined(__NetBSD__)
-#define RTDL_LAZY DL_LAZY
+#define RTLD_LAZY DL_LAZY
 #endif
 
 void
 plugin1_init(void)
 {
-	if (dlopen("./plugin2.so", RTDL_LAZY) == NULL)
+	if (dlopen("./plugin2.so", RTLD_LAZY | RTLD_GLOBAL) == NULL)
 		dlerror();
 	(void)printf("plugin1 initialized\n");
 }



dave...