[PATCH] bfd: Conditionally link against libdl for plugin support

[Meador Inge <meadori at codesourcery dot com>]

Hi All,

A few months back Kai fixed PR ld/12742 to enable plugins to work
with mingw host binaries.  With a current binutils source tree I can't
build for a i686-pc-mingw32 host (using Fedora MinGW 4.6.1-3.fc16)
because -ldl is unconditionally placed on the link line whenever
things are configured with --enable-plugins.

By my reading of PR ld/12742 others have gotten this to work.  I am not sure
how since the -ldl seems unconditional is support for plugins is enabled.  The
attached patch fixed things for me, but maybe I am missing something since
others seem to have gotten this to work with unpatched sources.

Comments?

2012-09-24  Meador Inge  <meadori@codesourcery.com>

	* Makefile.am (LIBDL): Use @plugin_libs@.
	* Makefile.in: Regenerated.
	* doc/Makefile.in: Likewise.
	* configure.in (plugin_libs): New variable.
	* configure: Regenerated.

diff --git a/bfd/Makefile.am b/bfd/Makefile.am
index 49f9662..8908c2c 100644
--- a/bfd/Makefile.am
+++ b/bfd/Makefile.am
@@ -35,7 +35,7 @@ AM_CFLAGS = $(WARN_CFLAGS)
 AM_CPPFLAGS = -DBINDIR='"$(bindir)"'
 if PLUGINS
 bfdinclude_HEADERS += $(INCDIR)/plugin-api.h
-LIBDL = -ldl
+LIBDL = @plugin_libs@
 endif
 
 # bfd.h goes here, for now
diff --git a/bfd/Makefile.in b/bfd/Makefile.in
index 5718fab..78177ad 100644
--- a/bfd/Makefile.in
+++ b/bfd/Makefile.in
@@ -297,6 +297,7 @@ mandir = @mandir@
 mkdir_p = @mkdir_p@
 oldincludedir = @oldincludedir@
 pdfdir = @pdfdir@
+plugin_libs = @plugin_libs@
 prefix = @prefix@
 program_transform_name = @program_transform_name@
 psdir = @psdir@
@@ -336,7 +337,7 @@ libbfd_la_LDFLAGS = $(am__append_1) -release `cat libtool-soversion` \
 @INSTALL_LIBBFD_FALSE@noinst_LTLIBRARIES = libbfd.la
 AM_CFLAGS = $(WARN_CFLAGS)
 AM_CPPFLAGS = -DBINDIR='"$(bindir)"'
-@PLUGINS_TRUE@LIBDL = -ldl
+@PLUGINS_TRUE@LIBDL = @plugin_libs@
 
 # bfd.h goes here, for now
 BFD_H = bfd.h
diff --git a/bfd/configure b/bfd/configure
index d81719d..5472b1d 100755
--- a/bfd/configure
+++ b/bfd/configure
@@ -660,6 +660,7 @@ REPORT_BUGS_TEXI
 REPORT_BUGS_TO
 PKGVERSION
 DEBUGDIR
+plugin_libs
 PLUGINS_FALSE
 PLUGINS_TRUE
 OTOOL64
@@ -11414,7 +11415,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11417 "configure"
+#line 11418 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11520,7 +11521,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11523 "configure"
+#line 11524 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -12003,6 +12004,7 @@ else
   PLUGINS_FALSE=
 fi
 
+plugin_libs=''
 
 if test "$plugins" = "yes"; then
   if test "$enable_dlopen" != "yes" ; then
@@ -12010,7 +12012,65 @@ if test "$plugins" = "yes"; then
       Building BFD with plugin support requires a host that supports -ldl." "$LINENO" 5
   fi
   enable_targets="$enable_targets plugin"
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking for library containing dlopen" >&5
+$as_echo_n "checking for library containing dlopen... " >&6; }
+if test "${ac_cv_search_dlopen+set}" = set; then :
+  $as_echo_n "(cached) " >&6
+else
+  ac_func_search_save_LIBS=$LIBS
+cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+/* Override any GCC internal prototype to avoid an error.
+   Use char because int might match the return type of a GCC
+   builtin and then its argument prototype would still apply.  */
+#ifdef __cplusplus
+extern "C"
+#endif
+char dlopen ();
+int
+main ()
+{
+return dlopen ();
+  ;
+  return 0;
+}
+_ACEOF
+for ac_lib in '' dl; do
+  if test -z "$ac_lib"; then
+    ac_res="none required"
+  else
+    ac_res=-l$ac_lib
+    LIBS="-l$ac_lib  $ac_func_search_save_LIBS"
+  fi
+  if ac_fn_c_try_link "$LINENO"; then :
+  ac_cv_search_dlopen=$ac_res
+fi
+rm -f core conftest.err conftest.$ac_objext \
+    conftest$ac_exeext
+  if test "${ac_cv_search_dlopen+set}" = set; then :
+  break
 fi
+done
+if test "${ac_cv_search_dlopen+set}" = set; then :
+
+else
+  ac_cv_search_dlopen=no
+fi
+rm conftest.$ac_ext
+LIBS=$ac_func_search_save_LIBS
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_search_dlopen" >&5
+$as_echo "$ac_cv_search_dlopen" >&6; }
+ac_res=$ac_cv_search_dlopen
+if test "$ac_res" != no; then :
+  test "$ac_res" = "none required" || LIBS="$ac_res $LIBS"
+  plugin_libs="-ldl"
+fi
+
+fi
+
+
 
 # Check whether --enable-64-bit-bfd was given.
 if test "${enable_64_bit_bfd+set}" = set; then :
diff --git a/bfd/configure.in b/bfd/configure.in
index 612d032..f86079d 100644
--- a/bfd/configure.in
+++ b/bfd/configure.in
@@ -29,6 +29,7 @@ LT_INIT([dlopen])
 ACX_LARGEFILE
 
 AM_CONDITIONAL(PLUGINS, test "$plugins" = "yes")
+plugin_libs=''
 
 if test "$plugins" = "yes"; then
   if test "$enable_dlopen" != "yes" ; then
@@ -36,8 +37,11 @@ if test "$plugins" = "yes"; then
       Building BFD with plugin support requires a host that supports -ldl.])
   fi
   enable_targets="$enable_targets plugin"
+  AC_SEARCH_LIBS([dlopen], [dl], [plugin_libs="-ldl"])
 fi
 
+AC_SUBST(plugin_libs)
+
 AC_ARG_ENABLE(64-bit-bfd,
 [  --enable-64-bit-bfd     64-bit support (on hosts with narrower word sizes)],
 [case "${enableval}" in
diff --git a/bfd/doc/Makefile.in b/bfd/doc/Makefile.in
index 7ba351d..169e9d5 100644
--- a/bfd/doc/Makefile.in
+++ b/bfd/doc/Makefile.in
@@ -251,6 +251,7 @@ mandir = @mandir@
 mkdir_p = @mkdir_p@
 oldincludedir = @oldincludedir@
 pdfdir = @pdfdir@
+plugin_libs = @plugin_libs@
 prefix = @prefix@
 program_transform_name = @program_transform_name@
 psdir = @psdir@