Index: src/bfd/pe-x86_64.c
===================================================================
--- src.orig/bfd/pe-x86_64.c	2010-04-17 16:30:01.126279000 +0200
+++ src/bfd/pe-x86_64.c	2010-04-22 08:20:25.604257600 +0200
@@ -28,7 +28,11 @@
 #define COFF_WITH_PE
 #define COFF_WITH_pex64
 #define PCRELOFFSET 		TRUE
+#if defined (USE_MINGW64_LEADING_UNDERSCORES)
 #define TARGET_UNDERSCORE 	'_'
+#else
+#define TARGET_UNDERSCORE 	0
+#endif
 #define COFF_LONG_SECTION_NAMES
 #define COFF_SUPPORT_GNU_LINKONCE
 #define COFF_LONG_FILENAMES
Index: src/bfd/pei-x86_64.c
===================================================================
--- src.orig/bfd/pei-x86_64.c	2010-04-17 16:30:01.129279000 +0200
+++ src/bfd/pei-x86_64.c	2010-04-22 08:20:25.610257600 +0200
@@ -29,7 +29,11 @@
 #define COFF_WITH_PE
 #define COFF_WITH_pex64
 #define PCRELOFFSET 		TRUE
+#if defined (USE_MINGW64_LEADING_UNDERSCORES)
 #define TARGET_UNDERSCORE 	'_'
+#else
+#define TARGET_UNDERSCORE 	0
+#endif
 /* Long section names not allowed in executable images, only object files.  */
 #define COFF_LONG_SECTION_NAMES 0
 #define COFF_SUPPORT_GNU_LINKONCE
Index: src/bfd/config.bfd
===================================================================
--- src.orig/bfd/config.bfd	2010-04-17 16:30:01.121279000 +0200
+++ src/bfd/config.bfd	2010-04-17 16:30:14.389279200 +0200
@@ -639,7 +639,7 @@ case "${targ}" in
     targ_defvec=x86_64pe_vec
     targ_selvecs="x86_64pe_vec x86_64pei_vec bfd_elf64_x86_64_vec bfd_elf64_l1om_vec"
     want64=true
-    targ_underscore=yes
+    targ_underscore=no
     ;;
 #endif
   i[3-7]86-*-lynxos*)
Index: src/binutils/dlltool.c
===================================================================
--- src.orig/binutils/dlltool.c	2010-04-17 16:30:01.133279000 +0200
+++ src/binutils/dlltool.c	2010-04-22 08:20:25.617257600 +0200
@@ -4143,6 +4143,16 @@ main (int ac, char **av)
   /* Check if we generated PE+.  */
   create_for_pep = strcmp (mname, "i386:x86-64") == 0;
 
+  {
+    /* Check the default underscore */
+    int u = leading_underscore; /* Underscoring mode. -1 for use default.  */
+    if (u == -1)
+      bfd_get_target_info (mtable[machine].how_bfd_target, NULL, 
+                           NULL, &u, NULL);
+    if (u != -1)
+      leading_underscore = (u != 0 ? TRUE : FALSE);
+  }
+
   if (!dll_name && exp_name)
     {
       /* If we are inferring dll_name from exp_name,
Index: src/bfd/coffcode.h
===================================================================
--- src.orig/bfd/coffcode.h	2010-04-17 16:30:01.117279000 +0200
+++ src/bfd/coffcode.h	2010-04-17 17:02:06.752279200 +0200
@@ -2648,7 +2648,7 @@ coff_write_relocs (bfd * abfd, int first
 	     entries know which symbol index they point to.  So we
 	     have to look up the output symbol here.  */
 
-	  if (q->sym_ptr_ptr[0]->the_bfd != abfd)
+	  if (q->sym_ptr_ptr[0] != NULL && q->sym_ptr_ptr[0]->the_bfd != abfd)
 	    {
 	      int j;
 	      const char *sname = q->sym_ptr_ptr[0]->name;
@@ -2677,7 +2677,7 @@ coff_write_relocs (bfd * abfd, int first
 	    n.r_symndx = q->addend;
 	  else
 #endif
-	    if (q->sym_ptr_ptr)
+	    if (q->sym_ptr_ptr && q->sym_ptr_ptr[0] != NULL)
 	      {
 #ifdef SECTION_RELATIVE_ABSOLUTE_SYMBOL_P
 		if (SECTION_RELATIVE_ABSOLUTE_SYMBOL_P (q, s))
Index: src/ld/pe-dll.c
===================================================================
--- src.orig/ld/pe-dll.c	2010-04-05 10:57:35.000000000 +0200
+++ src/ld/pe-dll.c	2010-04-18 12:53:58.338184400 +0200
@@ -385,7 +385,7 @@ static const autofilter_entry_type autof
   { STRING_COMMA_LEN ("__rtti_") },
   { STRING_COMMA_LEN ("__builtin_") },
   /* Don't re-export auto-imported symbols.  */
-  { STRING_COMMA_LEN ("_nm_") },
+  { STRING_COMMA_LEN ("__nm_") },
   /* Don't export symbols specifying internal DLL layout.  */
   { STRING_COMMA_LEN ("_head_") },
   { STRING_COMMA_LEN ("_IMPORT_DESCRIPTOR_") },
@@ -2135,11 +2135,11 @@ make_one (def_file_export *exp, bfd *par
       /* Symbol to reference ord/name of imported
 	 data symbol, used to implement auto-import.  */
       if (exp->flag_data)
-	quick_symbol (abfd, U ("_nm_"), U (""), exp->internal_name, id6,
+	quick_symbol (abfd, "__nm_", U (""), exp->internal_name, id6,
 		      BSF_GLOBAL,0);
     }
   if (pe_dll_compat_implib)
-    quick_symbol (abfd, U ("__imp_"), exp->internal_name, "", id5,
+    quick_symbol (abfd, "___imp_", exp->internal_name, "", id5,
 		  BSF_GLOBAL, 0);
 
   if (include_jmp_stub)
@@ -2286,7 +2286,7 @@ make_singleton_name_imp (const char *imp
   symptr = 0;
   symtab = xmalloc (3 * sizeof (asymbol *));
   id5 = quick_section (abfd, ".idata$5", SEC_HAS_CONTENTS, 2);
-  quick_symbol (abfd, U ("_imp_"), import, "", id5, BSF_GLOBAL, 0);
+  quick_symbol (abfd, "__imp_", import, "", id5, BSF_GLOBAL, 0);
 
   /* We need space for the real thunk and for the null terminator.  */
   bfd_set_section_size (abfd, id5, PE_IDATA5_SIZE * 2);
@@ -2327,8 +2327,8 @@ make_singleton_name_thunk (const char *i
   symptr = 0;
   symtab = xmalloc (3 * sizeof (asymbol *));
   id4 = quick_section (abfd, ".idata$4", SEC_HAS_CONTENTS, 2);
-  quick_symbol (abfd, U ("_nm_thnk_"), import, "", id4, BSF_GLOBAL, 0);
-  quick_symbol (abfd, U ("_nm_"), import, "", UNDSEC, BSF_GLOBAL, 0);
+  quick_symbol (abfd, "__nm_thnk_", import, "", id4, BSF_GLOBAL, 0);
+  quick_symbol (abfd, "__nm_", import, "", UNDSEC, BSF_GLOBAL, 0);
 
   /* We need space for the real thunk and for the null terminator.  */
   bfd_set_section_size (abfd, id4, PE_IDATA4_SIZE * 2);
@@ -2420,12 +2420,12 @@ make_import_fixup_entry (const char *nam
   symtab = xmalloc (6 * sizeof (asymbol *));
   id2 = quick_section (abfd, ".idata$2", SEC_HAS_CONTENTS, 2);
 
-  quick_symbol (abfd, U ("_nm_thnk_"), name, "", UNDSEC, BSF_GLOBAL, 0);
+  quick_symbol (abfd, "__nm_thnk_", name, "", UNDSEC, BSF_GLOBAL, 0);
   quick_symbol (abfd, U (""), symname, "_iname", UNDSEC, BSF_GLOBAL, 0);
   /* For relocator v2 we have to use the .idata$5 element and not 
      fixup_name.  */
   if (link_info.pei386_runtime_pseudo_reloc == 2)
-    quick_symbol (abfd, U ("_imp_"), name, "", UNDSEC, BSF_GLOBAL, 0);
+    quick_symbol (abfd, "__imp_", name, "", UNDSEC, BSF_GLOBAL, 0);
   else
     quick_symbol (abfd, "", fixup_name, "", UNDSEC, BSF_GLOBAL, 0);
 
@@ -2495,7 +2495,7 @@ make_runtime_pseudo_reloc (const char *n
 		  size += 12;
 		  runtime_pseudp_reloc_v2_init = 1;
 	    }
-      quick_symbol (abfd, U ("_imp_"), name, "", UNDSEC, BSF_GLOBAL, 0);
+      quick_symbol (abfd, "__imp_", name, "", UNDSEC, BSF_GLOBAL, 0);
 
       bfd_set_section_size (abfd, rt_rel, size);
       rt_rel_d = xmalloc (size);
@@ -2588,10 +2588,10 @@ pe_create_import_fixup (arelent *rel, as
   bfd *b;
   int need_import_table = 1;
 
-  sprintf (buf, U ("_imp_%s"), name);
+  sprintf (buf, "__imp_%s", name);
   name_imp_sym = bfd_link_hash_lookup (link_info.hash, buf, 0, 0, 1);
 
-  sprintf (buf, U ("_nm_thnk_%s"), name);
+  sprintf (buf, "__nm_thnk_%s", name);
 
   name_thunk_sym = bfd_link_hash_lookup (link_info.hash, buf, 0, 0, 1);
 
@@ -2803,8 +2803,9 @@ pe_undef_alias_cdecl_match (struct bfd_l
 
   sl = strlen (string);
   if (h->type == bfd_link_hash_undefined
-      && ((*hs == '@' && *string == '_'
-	   && strncmp (hs + 1, string + 1, sl - 1) == 0)
+      && ((*hs == '@' && (!pe_details->underscored || *string == '_')
+	   && strncmp (hs + 1, string + (pe_details->underscored != 0),
+		       sl - (pe_details->underscored != 0)) == 0)
 	  || strncmp (hs, string, sl) == 0)
       && h->root.string[sl] == '@')
     {
@@ -3149,7 +3150,7 @@ pe_implied_import_dll (const char *filen
 
       /* Skip unwanted symbols, which are
 	 exported in buggy auto-import releases.  */
-      if (! CONST_STRNEQ (erva + name_rva, "_nm_"))
+      if (! CONST_STRNEQ (erva + name_rva, "__nm_"))
  	{
  	  /* is_data is true if the address is in the data, rdata or bss
 	     segment.  */
Index: src/bfd/config.in
===================================================================
--- src.orig/bfd/config.in	2010-04-17 16:28:39.000000000 +0200
+++ src/bfd/config.in	2010-04-22 08:20:25.570257600 +0200
@@ -297,6 +297,9 @@
 /* Use b modifier when opening binary files? */
 #undef USE_BINARY_FOPEN
 
+/* Define if we should use leading underscore on 64 bit mingw targets */
+#undef USE_MINGW64_LEADING_UNDERSCORES
+
 /* Use mmap if it's available? */
 #undef USE_MMAP
 
Index: src/bfd/configure
===================================================================
--- src.orig/bfd/configure	2010-04-17 16:28:39.000000000 +0200
+++ src/bfd/configure	2010-04-22 08:20:25.588257600 +0200
@@ -785,6 +785,7 @@ enable_64_bit_bfd
 enable_targets
 with_mmap
 enable_secureplt
+enable_leading_mingw64_underscores
 with_separate_debug_dir
 enable_elf_stt_common
 with_pkgversion
@@ -1435,6 +1436,8 @@ Optional Features:
   --enable-64-bit-bfd     64-bit support (on hosts with narrower word sizes)
   --enable-targets        alternative target configurations
   --enable-secureplt      Default to creating read-only plt entries
+  --enable-leading-mingw64-underscores
+                          Enable leading underscores on 64 bit mingw targets
   --enable-elf-stt-common Allow the generation of ELF symbols with the STT_COMMON type
   --enable-werror         treat compile warnings as errors
   --enable-build-warnings enable build-time compiler warnings
@@ -11402,7 +11405,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11405 "configure"
+#line 11408 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -11508,7 +11511,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 11511 "configure"
+#line 11514 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -12049,6 +12052,17 @@ $as_echo "#define USE_SECUREPLT 1" >>con
 
 fi
 
+# Check whether --enable-leading-mingw64-underscores was given.
+if test "${enable_leading_mingw64_underscores+set}" = set; then :
+  enableval=$enable_leading_mingw64_underscores;
+fi
+
+if  test x"$enable_leading_mingw64_underscores" = xyes ; then :
+
+$as_echo "#define USE_MINGW64_LEADING_UNDERSCORES 1" >>confdefs.h
+
+fi
+
 DEBUGDIR=${libdir}/debug
 
 # Check whether --with-separate-debug-dir was given.
Index: src/bfd/configure.in
===================================================================
--- src.orig/bfd/configure.in	2010-04-17 16:28:39.000000000 +0200
+++ src/bfd/configure.in	2010-04-22 08:20:25.600257600 +0200
@@ -75,6 +75,14 @@ if test $use_secureplt = true; then
     [Define if we should default to creating read-only plt entries])
 fi
 
+AC_ARG_ENABLE(leading-mingw64-underscores,
+  AS_HELP_STRING([--enable-leading-mingw64-underscores],
+                 [Enable leading underscores on 64 bit mingw targets]),
+  [],[])
+AS_IF([ test x"$enable_leading_mingw64_underscores" = xyes ],
+  [AC_DEFINE(USE_MINGW64_LEADING_UNDERSCORES, 1,
+    [Define if we should use leading underscore on 64 bit mingw targets])])
+
 DEBUGDIR=${libdir}/debug
 AC_ARG_WITH(separate-debug-dir,
   AS_HELP_STRING([--with-separate-debug-dir=DIR],
Index: src/binutils/testsuite/binutils-all/dlltool.exp
===================================================================
--- src.orig/binutils/testsuite/binutils-all/dlltool.exp	2010-03-31 18:24:03.000000000 +0200
+++ src/binutils/testsuite/binutils-all/dlltool.exp	2010-04-25 11:24:40.781403600 +0200
@@ -14,13 +14,14 @@
 # along with this program; if not, write to the Free Software
 # Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA.
 
-if {![istarget "i*86-*-*"] && ![istarget "x86_64-*-mingw*"] } {
+if {![istarget "i*86-*-*"] && ![istarget "x86_64-*-mingw*"] && ![istarget "arm-*-pe*]} {
     return
 }
 
 if {![istarget "i*86-*-*pe*"] \
     && ![istarget "i*86-*-cygwin*"] \
     && ![istarget "i*86-*-mingw32*"] \
+    && ![istarget "arm-*-pe*"] \
     && ![istarget "x86_64-*-mingw*"] } {
     set target_xfail "yes"
 } else {
@@ -35,8 +36,8 @@ if {[which $DLLTOOL] == 0} then {
     return
 }
 
-verbose "$DLLTOOL -d $srcdir/$subdir/fastcall.def" 1
-catch "exec $DLLTOOL -d $srcdir/$subdir/fastcall.def" err
+verbose "$DLLTOOL --leading-underscore -d $srcdir/$subdir/fastcall.def" 1
+catch "exec $DLLTOOL --leading-underscore -d $srcdir/$subdir/fastcall.def" err
 
 if ![string match "" $err] then {
     send_log "$err\n"
@@ -50,8 +51,8 @@ if { "$target_xfail" == "yes" } {
     setup_xfail *-*
 }
 
-verbose "$DLLTOOL -p prefix -l tmpdir/libalias.a -d $srcdir/$subdir/alias.def $dlltool_gas_flag" 1
-catch "exec $DLLTOOL -p prefix -l tmpdir/libalias.a -d $srcdir/$subdir/alias.def $dlltool_gas_flag" err
+verbose "$DLLTOOL -p prefix --leading-underscore -l tmpdir/libalias.a -d $srcdir/$subdir/alias.def $dlltool_gas_flag" 1
+catch "exec $DLLTOOL -p prefix --leading-underscore -l tmpdir/libalias.a -d $srcdir/$subdir/alias.def $dlltool_gas_flag" err
 
 if ![string match "" $err] then {
     send_log "$err\n"
@@ -80,8 +81,8 @@ if [regexp $want $got] then {
     fail "dlltool -p (import name)"
 }
 
-verbose "$DLLTOOL -p prefix -l tmpdir/libalias2.a -d $srcdir/$subdir/alias-2.def $dlltool_gas_flag" 1
-catch "exec $DLLTOOL -p prefix -l tmpdir/libalias2.a -d $srcdir/$subdir/alias-2.def $dlltool_gas_flag" err
+verbose "$DLLTOOL -p prefix --leading-underscore -l tmpdir/libalias2.a -d $srcdir/$subdir/alias-2.def $dlltool_gas_flag" 1
+catch "exec $DLLTOOL -p prefix --leading-underscore -l tmpdir/libalias2.a -d $srcdir/$subdir/alias-2.def $dlltool_gas_flag" err
 
 if ![string match "" $err] then {
     send_log "$err\n"