Windows: Stop calling SetProcessDEPPolicy() on 64-bit Windows

It is not supported, and always fails. Some compilers warn about the
function pointer cast on 64-bit Windows.

Fixes bug 27461; bugfix on 0.2.2.23-alpha.

changes/bug27461

@@ -0,0 +1,5 @@
+  o Minor bugfixes (compilation):
+    - Stop calling SetProcessDEPPolicy() on 64-bit Windows. It is not
+      supported, and always fails. Some compilers warn about the function
+      pointer cast on 64-bit Windows.
+      Fixes bug 27461; bugfix on 0.2.2.23-alpha.

src/or/main.c

@@ -3433,6 +3433,13 @@ tor_main(int argc, char *argv[])
 #endif
   /* On heap corruption, just give up; don't try to play along. */
   HeapSetInformation(NULL, HeapEnableTerminationOnCorruption, NULL, 0);
+
+  /* SetProcessDEPPolicy is only supported on 32-bit Windows.
+   * (On 64-bit Windows it always fails, and some compilers don't like the
+   * PSETDEP cast.)
+   * 32-bit Windows defines _WIN32.
+   * 64-bit Windows defines _WIN32 and _WIN64. */
+#ifndef _WIN64
   /* Call SetProcessDEPPolicy to permanently enable DEP.
      The function will not resolve on earlier versions of Windows,
      and failure is not dangerous. */
@@ -3446,6 +3453,7 @@ tor_main(int argc, char *argv[])
       setdeppolicy(3);
     }
   }
+#endif /* !defined(_WIN64) */
 #endif
 
   configure_backtrace_handler(get_version());