Backport Pavel Chupin's fixes for mingw gold plugins

Changelog modified to reflect minor changes, for
 original patch and changelog, see the links.

Thread starts in December:
http://sourceware.org/ml/binutils/2012-12/msg00255.html
..continues into January:
http://sourceware.org/ml/binutils/2013-01/msg00061.html
..and ends with the final version by Ian Lance Taylor:
http://sourceware.org/ml/binutils/2013-01/msg00167.html

ChangeLog:

2012-12-25  Pavel Chupin  <[hidden email]>

       Fix mingw gold build with plugins enabled.
       * gold/Makefile.am: Replace -ldl with @DLOPEN_LIBS@.
       * gold/configure.ac: Export DLOPEN_LIBS, add headers check.
       * gold/plugin.cc: Handle non-dlfcn case.
       * gold/Makefile.in: Regenerate.
       * gold/config.in: Regenerate.
       * gold/configure: Regenerate.
       * gold/testsuite/Makefile.in: Regenerate.

7 files changed, 79 insertions, 2 deletions

diff --git a/binutils-2.21/gold/Makefile.am b/binutils-2.21/gold/Makefile.am
index c1c3588..a8daef6 100644
--- a/binutils-2.21/gold/Makefile.am
+++ b/binutils-2.21/gold/Makefile.am
@@ -20,7 +20,7 @@ AM_CPPFLAGS = \
 LIBIBERTY = ../libiberty/libiberty.a
 
 if PLUGINS
-LIBDL = -ldl
+LIBDL = @DLOPEN_LIBS@
 endif
 
 if THREADS
diff --git a/binutils-2.21/gold/Makefile.in b/binutils-2.21/gold/Makefile.in
index aad0f3a..63369ea 100644
--- a/binutils-2.21/gold/Makefile.in
+++ b/binutils-2.21/gold/Makefile.in
@@ -246,6 +246,7 @@ CYGPATH_W = @CYGPATH_W@
 DATADIRNAME = @DATADIRNAME@
 DEFS = @DEFS@
 DEPDIR = @DEPDIR@
+DLOPEN_LIBS = @DLOPEN_LIBS@
 ECHO_C = @ECHO_C@
 ECHO_N = @ECHO_N@
 ECHO_T = @ECHO_T@
@@ -371,7 +372,7 @@ AM_CPPFLAGS = \
 	@INCINTL@
 
 LIBIBERTY = ../libiberty/libiberty.a
-@PLUGINS_TRUE@LIBDL = -ldl
+@PLUGINS_TRUE@LIBDL = @DLOPEN_LIBS@
 @THREADS_TRUE@THREADSLIB = -lpthread
 AM_YFLAGS = -d
 
diff --git a/binutils-2.21/gold/config.in b/binutils-2.21/gold/config.in
index 8611376..c96189d 100644
--- a/binutils-2.21/gold/config.in
+++ b/binutils-2.21/gold/config.in
@@ -66,6 +66,9 @@
    don't. */
 #undef HAVE_DECL_VSNPRINTF
 
+/* Define to 1 if you have the <dlfcn.h> header file. */
+#undef HAVE_DLFCN_H
+
 /* Define to 1 if you have the <ext/hash_map> header file. */
 #undef HAVE_EXT_HASH_MAP
 
@@ -162,6 +165,9 @@
 /* Define to 1 if you have the <unistd.h> header file. */
 #undef HAVE_UNISTD_H
 
+/* Define to 1 if you have the <windows.h> header file. */
+#undef HAVE_WINDOWS_H
+
 /* Define to 1 if you have the <zlib.h> header file. */
 #undef HAVE_ZLIB_H
 
diff --git a/binutils-2.21/gold/configure b/binutils-2.21/gold/configure
index 56a6116..ec510d2 100755
--- a/binutils-2.21/gold/configure
+++ b/binutils-2.21/gold/configure
@@ -594,6 +594,7 @@ LTLIBOBJS
 MAINT
 MAINTAINER_MODE_FALSE
 MAINTAINER_MODE_TRUE
+DLOPEN_LIBS
 CXXCPP
 HAVE_ZLIB_FALSE
 HAVE_ZLIB_TRUE
@@ -6941,6 +6942,35 @@ fi
 
 done
 
+
+for ac_header in windows.h
+do :
+  ac_fn_cxx_check_header_mongrel "$LINENO" "windows.h" "ac_cv_header_windows_h" "$ac_includes_default"
+if test "x$ac_cv_header_windows_h" = x""yes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_WINDOWS_H 1
+_ACEOF
+
+fi
+
+done
+
+for ac_header in dlfcn.h
+do :
+  ac_fn_cxx_check_header_mongrel "$LINENO" "dlfcn.h" "ac_cv_header_dlfcn_h" "$ac_includes_default"
+if test "x$ac_cv_header_dlfcn_h" = x""yes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_DLFCN_H 1
+_ACEOF
+ DLOPEN_LIBS="-ldl"
+else
+  DLOPEN_LIBS=""
+fi
+
+done
+
+
+
 for ac_func in mallinfo posix_fallocate readv sysconf times
 do :
   as_ac_var=`$as_echo "ac_cv_func_$ac_func" | $as_tr_sh`
diff --git a/binutils-2.21/gold/configure.ac b/binutils-2.21/gold/configure.ac
index 1bceb1e..41d3552 100644
--- a/binutils-2.21/gold/configure.ac
+++ b/binutils-2.21/gold/configure.ac
@@ -445,6 +445,13 @@ AC_LANG_PUSH(C++)
 AC_CHECK_HEADERS(tr1/unordered_set tr1/unordered_map)
 AC_CHECK_HEADERS(ext/hash_map ext/hash_set)
 AC_CHECK_HEADERS(byteswap.h)
+
+dnl When plugins enabled dynamic loader interface is required. Check headers
+dnl which may provide this interface. In case of dlfcn.h add libdl to link.
+AC_CHECK_HEADERS(windows.h)
+AC_CHECK_HEADERS(dlfcn.h, [DLOPEN_LIBS="-ldl"], [DLOPEN_LIBS=""])
+AC_SUBST(DLOPEN_LIBS)
+
 AC_CHECK_FUNCS(mallinfo posix_fallocate readv sysconf times)
 AC_CHECK_DECLS([basename, ffs, asprintf, vasprintf, snprintf, vsnprintf, strverscmp, strndup, memmem])
 
diff --git a/binutils-2.21/gold/plugin.cc b/binutils-2.21/gold/plugin.cc
index 8ce152c..aab0410 100644
--- a/binutils-2.21/gold/plugin.cc
+++ b/binutils-2.21/gold/plugin.cc
@@ -29,9 +29,39 @@
 #include <vector>
 
 #ifdef ENABLE_PLUGINS
+#ifdef HAVE_DLFCN_H
 #include <dlfcn.h>
+#elif defined (HAVE_WINDOWS_H)
+#include <windows.h>
+#else
+#error Unknown how to handle dynamic-load-libraries.
 #endif
 
+#if !defined (HAVE_DLFCN_H) && defined (HAVE_WINDOWS_H)
+
+#define RTLD_NOW 0      /* Dummy value.  */
+static void *
+dlopen(const char *file, int mode ATTRIBUTE_UNUSED)
+{
+  return LoadLibrary(file);
+}
+
+static void *
+dlsym(void *handle, const char *name)
+{
+  return reinterpret_cast<void *>(
+     GetProcAddress(static_cast<HMODULE>(handle),name));
+}
+
+static const char *
+dlerror(void)
+{
+  return "unable to load dll";
+}
+
+#endif /* !defined (HAVE_DLFCN_H) && defined (HAVE_WINDOWS_H)  */
+#endif /* ENABLE_PLUGINS */
+
 #include "parameters.h"
 #include "errors.h"
 #include "fileread.h"
diff --git a/binutils-2.21/gold/testsuite/Makefile.in b/binutils-2.21/gold/testsuite/Makefile.in
index 4b1cd54..77d4351 100644
--- a/binutils-2.21/gold/testsuite/Makefile.in
+++ b/binutils-2.21/gold/testsuite/Makefile.in
@@ -1750,6 +1750,7 @@ CYGPATH_W = @CYGPATH_W@
 DATADIRNAME = @DATADIRNAME@
 DEFS = @DEFS@
 DEPDIR = @DEPDIR@
+DLOPEN_LIBS = @DLOPEN_LIBS@
 ECHO_C = @ECHO_C@
 ECHO_N = @ECHO_N@
 ECHO_T = @ECHO_T@
@@ -1757,6 +1758,8 @@ EGREP = @EGREP@
 EXEEXT = @EXEEXT@
 GENCAT = @GENCAT@
 GMSGFMT = @GMSGFMT@
+GOLD_LDADD = @GOLD_LDADD@
+GOLD_LDFLAGS = @GOLD_LDFLAGS@
 GREP = @GREP@
 INCINTL = @INCINTL@
 INSTALL = @INSTALL@