Auto merge of #809 - RalfJung:intptrcast, r=RalfJung

use intptrcast for heap_allocator test; then it should work on Windows

tests/run-pass/heap_allocator.rs

@@ -1,3 +1,4 @@
+// compile-flags: -Zmiri-seed=
 #![feature(allocator_api)]
 
 use std::ptr::NonNull;
@@ -32,8 +33,8 @@ fn check_overalign_requests<T: Alloc>(mut allocator: T) {
     let size = 8;
     // Greater than `size`.
     let align = 16;
-    // Miri is deterministic; no need to try many times.
-    let iterations = 1;
+
+    let iterations = 5;
     unsafe {
         let pointers: Vec<_> = (0..iterations).map(|_| {
             allocator.alloc(Layout::from_size_align(size, align).unwrap()).unwrap()
@@ -75,7 +76,6 @@ fn box_to_global() {
 fn main() {
     check_alloc(System);
     check_alloc(Global);
-    #[cfg(not(target_os = "windows"))] // TODO: Inspects allocation base address on Windows; needs intptrcast model
     check_overalign_requests(System);
     check_overalign_requests(Global);
     global_to_box();