diff --git i/ext/dl/dl.c w/ext/dl/dl.c
index 200c1d6..856ef78 100644
--- i/ext/dl/dl.c
+++ w/ext/dl/dl.c
@@ -17,6 +17,38 @@ VALUE rb_eDLTypeError;
 ID rbdl_id_cdecl;
 ID rbdl_id_stdcall;
 
+#ifndef DLTYPE_SSIZE_T
+# if SIZEOF_SIZE_T == SIZEOF_INT
+#   define DLTYPE_SSIZE_T DLTYPE_INT
+# elif SIZEOF_SIZE_T == SIZEOF_LONG
+#   define DLTYPE_SSIZE_T DLTYPE_LONG
+# elif defined HAVE_LONG_LONG && SIZEOF_SIZE_T == SIZEOF_LONG_LONG
+#   define DLTYPE_SSIZE_T DLTYPE_LONG_LONG
+# endif
+#endif
+#define DLTYPE_SIZE_T (SIGNEDNESS_OF_SIZE_T*DLTYPE_SSIZE_T)
+
+#ifndef DLTYPE_PTRDIFF_T
+# if SIZEOF_PTRDIFF_T == SIZEOF_INT
+#   define DLTYPE_PTRDIFF_T DLTYPE_INT
+# elif SIZEOF_PTRDIFF_T == SIZEOF_LONG
+#   define DLTYPE_PTRDIFF_T DLTYPE_LONG
+# elif defined HAVE_LONG_LONG && SIZEOF_PTRDIFF_T == SIZEOF_LONG_LONG
+#   define DLTYPE_PTRDIFF_T DLTYPE_LONG_LONG
+# endif
+#endif
+
+#ifndef DLTYPE_INTPTR_T
+# if SIZEOF_INTPTR_T == SIZEOF_INT
+#   define DLTYPE_INTPTR_T DLTYPE_INT
+# elif SIZEOF_INTPTR_T == SIZEOF_LONG
+#   define DLTYPE_INTPTR_T DLTYPE_LONG
+# elif defined HAVE_LONG_LONG && SIZEOF_INTPTR_T == SIZEOF_LONG_LONG
+#   define DLTYPE_INTPTR_T DLTYPE_LONG_LONG
+# endif
+#endif
+#define DLTYPE_UINTPTR_T (-DLTYPE_INTPTR_T)
+
 VALUE
 rb_dl_dlopen(int argc, VALUE argv[], VALUE self)
 {
@@ -271,6 +303,36 @@ Init_dl(void)
      */
     rb_define_const(rb_mDL, "TYPE_DOUBLE",  INT2NUM(DLTYPE_DOUBLE));
 
+    /* Document-const: TYPE_SIZE_T
+     *
+     * DL::CFunc type - size_t
+     */
+    rb_define_const(rb_mDL, "TYPE_SIZE_T",  INT2NUM(DLTYPE_SIZE_T));
+
+    /* Document-const: TYPE_SSIZE_T
+     *
+     * DL::CFunc type - ssize_t
+     */
+    rb_define_const(rb_mDL, "TYPE_SSIZE_T", INT2NUM(DLTYPE_SSIZE_T));
+
+    /* Document-const: TYPE_PTRDIFF_T
+     *
+     * DL::CFunc type - ptrdiff_t
+     */
+    rb_define_const(rb_mDL, "TYPE_PTRDIFF_T", INT2NUM(DLTYPE_PTRDIFF_T));
+
+    /* Document-const: TYPE_INTPTR_T
+     *
+     * DL::CFunc type - intptr_t
+     */
+    rb_define_const(rb_mDL, "TYPE_INTPTR_T", INT2NUM(DLTYPE_INTPTR_T));
+
+    /* Document-const: TYPE_UINTPTR_T
+     *
+     * DL::CFunc type - uintptr_t
+     */
+    rb_define_const(rb_mDL, "TYPE_UINTPTR_T", INT2NUM(DLTYPE_UINTPTR_T));
+
     /* Document-const: ALIGN_VOIDP
      *
      * The alignment size of a void*
@@ -321,6 +383,36 @@ Init_dl(void)
      */
     rb_define_const(rb_mDL, "ALIGN_DOUBLE",INT2NUM(ALIGN_DOUBLE));
 
+    /* Document-const: ALIGN_SIZE_T
+     *
+     * The alignment size of a size_t
+     */
+    rb_define_const(rb_mDL, "ALIGN_SIZE_T", INT2NUM(ALIGN_OF(size_t)));
+
+    /* Document-const: ALIGN_SSIZE_T
+     *
+     * The alignment size of a ssize_t
+     */
+    rb_define_const(rb_mDL, "ALIGN_SSIZE_T", INT2NUM(ALIGN_OF(size_t))); /* same as size_t */
+
+    /* Document-const: ALIGN_PTRDIFF_T
+     *
+     * The alignment size of a ptrdiff_t
+     */
+    rb_define_const(rb_mDL, "ALIGN_PTRDIFF_T", INT2NUM(ALIGN_OF(ptrdiff_t)));
+
+    /* Document-const: ALIGN_INTPTR_T
+     *
+     * The alignment size of a intptr_t
+     */
+    rb_define_const(rb_mDL, "ALIGN_INTPTR_T", INT2NUM(ALIGN_OF(intptr_t)));
+
+    /* Document-const: ALIGN_UINTPTR_T
+     *
+     * The alignment size of a uintptr_t
+     */
+    rb_define_const(rb_mDL, "ALIGN_UINTPTR_T", INT2NUM(ALIGN_OF(uintptr_t)));
+
     /* Document-const: SIZEOF_VOIDP
      *
      * size of a void*
@@ -371,6 +463,36 @@ Init_dl(void)
      */
     rb_define_const(rb_mDL, "SIZEOF_DOUBLE",INT2NUM(sizeof(double)));
 
+    /* Document-const: SIZEOF_SIZE_T
+     *
+     * size of a size_t
+     */
+    rb_define_const(rb_mDL, "SIZEOF_SIZE_T",  INT2NUM(sizeof(size_t)));
+
+    /* Document-const: SIZEOF_SSIZE_T
+     *
+     * size of a ssize_t
+     */
+    rb_define_const(rb_mDL, "SIZEOF_SSIZE_T",  INT2NUM(sizeof(size_t))); /* same as size_t */
+
+    /* Document-const: SIZEOF_PTRDIFF_T
+     *
+     * size of a ptrdiff_t
+     */
+    rb_define_const(rb_mDL, "SIZEOF_PTRDIFF_T",  INT2NUM(sizeof(ptrdiff_t)));
+
+    /* Document-const: SIZEOF_INTPTR_T
+     *
+     * size of a intptr_t
+     */
+    rb_define_const(rb_mDL, "SIZEOF_INTPTR_T",  INT2NUM(sizeof(intptr_t)));
+
+    /* Document-const: SIZEOF_UINTPTR_T
+     *
+     * size of a intptr_t
+     */
+    rb_define_const(rb_mDL, "SIZEOF_UINTPTR_T",  INT2NUM(sizeof(uintptr_t)));
+
     rb_define_module_function(rb_mDL, "dlwrap", rb_dl_value2ptr, 1);
     rb_define_module_function(rb_mDL, "dlunwrap", rb_dl_ptr2value, 1);
 
diff --git i/ext/dl/extconf.rb w/ext/dl/extconf.rb
index 6d4d6c5..4ef46f8 100644
--- i/ext/dl/extconf.rb
+++ w/ext/dl/extconf.rb
@@ -25,6 +25,19 @@ else
 end
 
 if check
+  config = File.read(RbConfig.expand(File.join($arch_hdrdir, "ruby/config.h")))
+  types = {"SIZE_T"=>"SSIZE_T", "PTRDIFF_T"=>nil, "INTPTR_T"=>nil}
+  types.each do |type, signed|
+    if /^\#define\s+SIZEOF_#{type}\s+(SIZEOF_(.+)|\d+)/ =~ config
+      if size = $2 and size != 'VOIDP'
+        size = types.fetch(size) {size}
+        $defs << format("-DDLTYPE_%s=DLTYPE_%s", signed||type, size)
+      end
+      if signed
+        check_signedness(type.downcase, "stddef.h")
+      end
+    end
+  end
   $defs << %[-DRUBY_VERSION=\\"#{RUBY_VERSION}\\"]
   create_makefile("dl")
 end
diff --git i/ext/dl/lib/dl/cparser.rb w/ext/dl/lib/dl/cparser.rb
index 210f953..7aae9ea 100644
--- i/ext/dl/lib/dl/cparser.rb
+++ w/ext/dl/lib/dl/cparser.rb
@@ -95,6 +95,16 @@ module DL
         return TYPE_FLOAT
       when "double"
         return TYPE_DOUBLE
+      when "size_t"
+        return TYPE_SIZE_T
+      when "ssize_t"
+        return TYPE_SSIZE_T
+      when "ptrdiff_t"
+        return TYPE_PTRDIFF_T
+      when "intptr_t"
+        return TYPE_INTPTR_T
+      when "uintptr_t"
+        return TYPE_UINTPTR_T
       when /\*/, /\[\s*\]/
         return TYPE_VOIDP
       else
diff --git i/ext/dl/lib/dl/types.rb w/ext/dl/lib/dl/types.rb
index 3dfa408..d5724e4 100644
--- i/ext/dl/lib/dl/types.rb
+++ w/ext/dl/lib/dl/types.rb
@@ -40,11 +40,7 @@ module DL
         typealias "UINT", "unsigned int"
         typealias "ULONG", "unsigned long"
         typealias "UCHAR", "unsigned char"
-        if [nil].pack('p').bytesize == 8
-          typealias "HANDLE", "unsigned long long"
-        else
-          typealias "HANDLE", "unsigned long"
-        end
+        typealias "HANDLE", "uintptr_t"
         typealias "PHANDLE", "void*"
         typealias "PVOID", "void*"
         typealias "LPCSTR", "char*"
diff --git i/ext/fiddle/extconf.rb w/ext/fiddle/extconf.rb
index 03b0ac2..da67545 100644
--- i/ext/fiddle/extconf.rb
+++ w/ext/fiddle/extconf.rb
@@ -19,6 +19,20 @@ end
 
 have_header 'sys/mman.h'
 
+config = File.read(RbConfig.expand(File.join($arch_hdrdir, "ruby/config.h")))
+types = {"SIZE_T"=>"SSIZE_T", "PTRDIFF_T"=>nil, "INTPTR_T"=>nil}
+types.each do |type, signed|
+  if /^\#define\s+SIZEOF_#{type}\s+(SIZEOF_(.+)|\d+)/ =~ config
+    if size = $2 and size != 'VOIDP'
+      size = types.fetch(size) {size}
+      $defs << format("-TYPE_%s=TYPE_%s", signed||type, size)
+    end
+    if signed
+      check_signedness(type.downcase, "stddef.h")
+    end
+  end
+end
+
 create_makefile 'fiddle'
 
 # :startdoc:
diff --git i/ext/fiddle/fiddle.c w/ext/fiddle/fiddle.c
index 83c0bb5..744d2f2 100644
--- i/ext/fiddle/fiddle.c
+++ w/ext/fiddle/fiddle.c
@@ -2,6 +2,38 @@
 
 VALUE mFiddle;
 
+#ifndef TYPE_SSIZE_T
+# if SIZEOF_SIZE_T == SIZEOF_INT
+#   define TYPE_SSIZE_T TYPE_INT
+# elif SIZEOF_SIZE_T == SIZEOF_LONG
+#   define TYPE_SSIZE_T TYPE_LONG
+# elif defined HAVE_LONG_LONG && SIZEOF_SIZE_T == SIZEOF_LONG_LONG
+#   define TYPE_SSIZE_T TYPE_LONG_LONG
+# endif
+#endif
+#define TYPE_SIZE_T (SIGNEDNESS_OF_SIZE_T*TYPE_SSIZE_T)
+
+#ifndef TYPE_PTRDIFF_T
+# if SIZEOF_PTRDIFF_T == SIZEOF_INT
+#   define TYPE_PTRDIFF_T TYPE_INT
+# elif SIZEOF_PTRDIFF_T == SIZEOF_LONG
+#   define TYPE_PTRDIFF_T TYPE_LONG
+# elif defined HAVE_LONG_LONG && SIZEOF_PTRDIFF_T == SIZEOF_LONG_LONG
+#   define TYPE_PTRDIFF_T TYPE_LONG_LONG
+# endif
+#endif
+
+#ifndef TYPE_INTPTR_T
+# if SIZEOF_INTPTR_T == SIZEOF_INT
+#   define TYPE_INTPTR_T TYPE_INT
+# elif SIZEOF_INTPTR_T == SIZEOF_LONG
+#   define TYPE_INTPTR_T TYPE_LONG
+# elif defined HAVE_LONG_LONG && SIZEOF_INTPTR_T == SIZEOF_LONG_LONG
+#   define TYPE_INTPTR_T TYPE_LONG_LONG
+# endif
+#endif
+#define TYPE_UINTPTR_T (-TYPE_INTPTR_T)
+
 void
 Init_fiddle(void)
 {
@@ -71,6 +103,24 @@ Init_fiddle(void)
      */
     rb_define_const(mFiddle, "TYPE_DOUBLE",    INT2NUM(TYPE_DOUBLE));
 
+    /* Document-const: TYPE_SSIZE_T
+     *
+     * C type - ssize_t
+     */
+    rb_define_const(mFiddle, "TYPE_SSIZE_T",   INT2NUM(TYPE_SSIZE_T));
+
+    /* Document-const: TYPE_PTRDIFF_T
+     *
+     * C type - ptrdiff_t
+     */
+    rb_define_const(mFiddle, "TYPE_PTRDIFF_T", INT2NUM(TYPE_PTRDIFF_T));
+
+    /* Document-const: TYPE_INTPTR_T
+     *
+     * C type - intptr_t
+     */
+    rb_define_const(mFiddle, "TYPE_INTPTR_T",  INT2NUM(TYPE_INTPTR_T));
+
     /* Document-const: WINDOWS
      *
      * Returns a boolean regarding whether the host is WIN32
diff --git i/test/ruby/memory_status.rb w/test/ruby/memory_status.rb
index 0dbfaa3..a26452b 100644
--- i/test/ruby/memory_status.rb
+++ w/test/ruby/memory_status.rb
@@ -22,11 +22,7 @@ module Memory
       extend DL::Importer
       dlload "kernel32.dll", "psapi.dll"
       include DL::Win32Types
-      if [nil].pack('p').bytesize == 8
-        typealias "SIZE_T", "DWORD64"
-      else
-        typealias "SIZE_T", "DWORD32"
-      end
+      typealias "SIZE_T", "size_t"
 
       PROCESS_MEMORY_COUNTERS = struct [
         "DWORD  cb",