Use a memset upcall to zero things without static alignment

This fixes issues #843 and #1546. The cost of an upcall is
unfortunate, though. I assume there must be a way to simply manually
compute the pointer or size, using something akin to the formula in
`align_to` in `rust_util.h`. I could not get this to work,
unfortunately.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/rt/rust_upcall.cpp b/src/rt/rust_upcall.cpp
index 65299a7d244..096c814f7c9 100644
--- a/src/rt/rust_upcall.cpp
+++ b/src/rt/rust_upcall.cpp
@@ -227,6 +227,15 @@ upcall_shared_free(void* ptr) {
     UPCALL_SWITCH_STACK(&args, upcall_s_shared_free);
 }
 
+/************************************************************************
+ * Memset that, contrary to the llvm intrinsic, handles dynamic alignment
+ */
+
+extern "C" CDECL void
+upcall_memset(void* ptr, char val, unsigned size, unsigned align) {
+    memset(ptr, val, align_to(size, align));
+}
+
 /**********************************************************************
  * Called to deep copy a type descriptor onto the exchange heap.
  * Used when sending closures.  It's possible that we should have