Patch: FYI: load libmagic dynamically

[Tom Tromey <tromey at redhat dot com>]

I'm checking this in.

Andrew wrote it, I just redid the configury and wrote the ChangeLog
entry.

This changes our use of libmagic to be really dynamic.  We ran into a
couple problems linking against it: static linking didn't work
properly, and some systems (I'm looking at you suse) only ship a
static libmagic.a.  Also on some systems it apparently interacted
poorly with multi-arch.

Tom

Index: ChangeLog
from  Andrew Haley  <aph@redhat.com>

	* configure, Makefile.in, include/config.h.in: Rebuilt.
	* Makefile.am (libgcj_la_LIBADD): Removed $(LIBMAGIC).
	* configure.ac: Don't check for libmagic.
	* java/net/natVMURLConnection.cc (p_magic_open, p_magic_load,
	p_magic_close, p_magic_buffer): New globals.
	(init): Look up 'magic' functions.
	(guessContentTypeFromBuffer): Updated.

Index: configure.ac
===================================================================
--- configure.ac	(revision 121138)
+++ configure.ac	(working copy)
@@ -1209,12 +1209,6 @@
       AC_CHECK_LIB(z, deflate, ZLIBSPEC=-lz, ZLIBSPEC=)
    fi
 
-   LIBMAGIC=
-   AC_CHECK_LIB(magic, magic_open, [
-      AC_DEFINE([HAVE_MAGIC_OPEN], 1, [Define if you have magic_open().])
-      LIBMAGIC="-lmagic"])
-   AC_SUBST(LIBMAGIC)
-
    # Test for Gtk stuff, if asked for.
    if test "$use_gtk_awt" = yes; then
       PKG_CHECK_MODULES(GTK, gtk+-2.0 >= 2.4)
Index: java/net/natVMURLConnection.cc
===================================================================
--- java/net/natVMURLConnection.cc	(revision 121138)
+++ java/net/natVMURLConnection.cc	(working copy)
@@ -1,4 +1,4 @@
-/* Copyright (C) 2006  Free Software Foundation
+/* Copyright (C) 2006, 2007  Free Software Foundation
 
    This file is part of libgcj.
 
@@ -11,46 +11,71 @@
 #include <java/net/VMURLConnection.h>
 #include <gcj/cni.h>
 #include <java/lang/UnsupportedOperationException.h>
+#include <stdio.h>
 
-#if defined (HAVE_MAGIC_H) && defined (HAVE_MAGIC_OPEN)
+#if defined (HAVE_MAGIC_H) && defined (USE_LTDL)
 
 #include <magic.h>
+#include <ltdl.h>
 
 static magic_t cookie;
 
-#endif /* HAVE_MAGIC_H && HAVE_MAGIC_OPEN */
+static magic_t (*p_magic_open)(int flags);
+static int (*p_magic_load)(magic_t cookie, const char *filename);
+static void (*p_magic_close)(magic_t cookie);
+static const char * (*p_magic_buffer) (magic_t cookie, const void *buffer,
+				       size_t length);
 
+#endif /* HAVE_MAGIC_H && defined (USE_LTDL) */
+
 void
 java::net::VMURLConnection::init ()
 {
-#if defined (HAVE_MAGIC_H) && defined (HAVE_MAGIC_OPEN)
-  cookie = magic_open (MAGIC_MIME);
+#if defined (HAVE_MAGIC_H) && defined (USE_LTDL)
+  lt_dlhandle handle = lt_dlopenext ("libmagic.so");
+  if (!handle)
+    return;
+
+  p_magic_open = (typeof (p_magic_open))lt_dlsym(handle, "magic_open");
+  if (p_magic_open == NULL)
+    return;
+  p_magic_buffer = (typeof (p_magic_buffer))lt_dlsym(handle, "magic_buffer");
+  if (p_magic_buffer == NULL)
+    return;
+  p_magic_close = (typeof (p_magic_close))lt_dlsym(handle, "magic_close");
+  if (p_magic_close == NULL)
+    return;
+  p_magic_load = (typeof (p_magic_load))lt_dlsym(handle, "magic_load");
+  if (p_magic_load == NULL)
+    return;
+
+  cookie = p_magic_open (MAGIC_MIME);
   if (cookie == (magic_t) NULL)
     return;
-  if (magic_load (cookie, NULL) == -1)
+  if (p_magic_load (cookie, NULL) == -1)
     {
-      magic_close (cookie);
+      p_magic_close (cookie);
       cookie = (magic_t) NULL;
     }
-#endif /* HAVE_MAGIC_H && HAVE_MAGIC_OPEN */
+#endif /* HAVE_MAGIC_H  && defined (USE_LTDL) */
 }
 
 ::java::lang::String *
 java::net::VMURLConnection::guessContentTypeFromBuffer (jbyteArray bytes,
 							jint valid)
 {
-#if defined (HAVE_MAGIC_H) && defined (HAVE_MAGIC_OPEN)
+#if defined (HAVE_MAGIC_H) && defined (USE_LTDL)
   const char *result;
 
   if (cookie == (magic_t) NULL)
     return NULL;
 
-  result = magic_buffer (cookie, elements(bytes), valid);
+  result = p_magic_buffer (cookie, elements(bytes), valid);
 
   if (result == NULL)
     return NULL;
   return _Jv_NewStringUTF (result);
 #else
   return NULL;
-#endif /* HAVE_MAGIC_H && HAVE_MAGIC_OPEN */
+#endif /* HAVE_MAGIC_H  && defined (USE_LTDL) */
 }
Index: Makefile.am
===================================================================
--- Makefile.am	(revision 121138)
+++ Makefile.am	(working copy)
@@ -240,7 +240,7 @@
 	$(all_packages_source_files:.list=.lo) \
 	$(bc_objects) \
 	$(propertyo_files) \
-	$(LIBMAGIC) $(LIBFFI) $(ZLIBS) $(GCLIBS)
+	$(LIBFFI) $(ZLIBS) $(GCLIBS)
 libgcj_la_DEPENDENCIES = libgcj-$(gcc_version).jar \
 	java/lang/Object.lo \
 	java/lang/Class.lo \