rustc: Mark an obstack fencepost when entering a dynamically-sized frame

src/comp/middle/trans.rs

@@ -466,6 +466,14 @@ fn alloca(cx: &@block_ctxt, t: TypeRef) -> ValueRef {
 }
 
 fn array_alloca(cx: &@block_ctxt, t: TypeRef, n: ValueRef) -> ValueRef {
+    alt bcx_fcx(cx).llobstacktoken {
+        none. {
+            bcx_fcx(cx).llobstacktoken =
+                some(cx.build.Call(bcx_ccx(cx).upcalls.dynastack_mark,
+                     ~[bcx_fcx(cx).lltaskptr]));
+        }
+        some(_) { /* no-op */ }
+    }
     ret new_builder(cx.fcx.lldynamicallocas).ArrayAlloca(t, n);
 }
 
@@ -5632,18 +5640,6 @@ fn llderivedtydescs_block_ctxt(fcx: &@fn_ctxt) -> @block_ctxt {
           fcx: fcx};
 }
 
-fn lldynamicallocas_block_ctxt(fcx: &@fn_ctxt) -> @block_ctxt {
-    let cleanups: [cleanup] = ~[];
-    ret @{llbb: fcx.lldynamicallocas,
-          build: new_builder(fcx.lldynamicallocas),
-          parent: parent_none,
-          kind: SCOPE_BLOCK,
-          mutable cleanups: cleanups,
-          sp: fcx.sp,
-          fcx: fcx};
-}
-
-
 
 fn alloc_ty(cx: &@block_ctxt, t: &ty::t) -> result {
     let bcx = cx;
@@ -5798,6 +5794,7 @@ fn new_fn_ctxt_w_id(cx: @local_ctxt, sp: &span, llfndecl: ValueRef,
           mutable llderivedtydescs_first: llbbs.dt,
           mutable llderivedtydescs: llbbs.dt,
           mutable lldynamicallocas: llbbs.da,
+          mutable llobstacktoken: none::<ValueRef>,
           mutable llself: none::<val_self_pair>,
           mutable lliterbody: none::<ValueRef>,
           mutable iterbodyty: none::<ty::t>,

src/comp/middle/trans_common.rs

@@ -214,6 +214,10 @@ type fn_ctxt = {
     // alloca'd by code in llallocas?
     mutable lldynamicallocas: BasicBlockRef,
 
+    // The token used to clear the dynamic allocas at the end of this frame.
+    // Will be |none| if there are no dynamic allocas.
+    mutable llobstacktoken: option::t<ValueRef>,
+
     // The 'self' object currently in use in this function, if there
     // is one.
     mutable llself: option::t<val_self_pair>,

src/rt/rust_obstack.cpp

@@ -58,6 +58,14 @@ rust_obstack::alloc_new(size_t len) {
     return chunk->alloc(len);
 }
 
+rust_obstack::~rust_obstack() {
+    while (chunk) {
+        rust_obstack_chunk *prev = chunk->prev;
+        task->free(chunk);
+        chunk = prev;
+    }
+}
+
 void *
 rust_obstack::alloc(size_t len) {
     if (!chunk)

src/rt/rust_obstack.h

@@ -15,6 +15,7 @@ class rust_obstack {
 
 public:
     rust_obstack(rust_task *in_task) : chunk(NULL), task(in_task) {}
+    ~rust_obstack();
 
     void *alloc(size_t len);
     void free(void *ptr);