Merge branch 'r3d/zero-leak' into lang/uifree

runtime/native/vk.ludic

@@ -28,6 +28,8 @@ import "vk_api.ludic"
 # Once a frame: on macOS drains what MoltenVK and the layer autoreleased during the last one (a
 # program pumping its own events has no other pool); nothing elsewhere.
 extern function vk_frame_pool() = "lvk_frame_pool"
+# malloc's live bytes (macOS; 0 elsewhere): a test that a path allocates nothing, frame after frame
+extern function vk_heap_bytes() -> long = "lvk_heap_bytes"
 extern function vk_sl_prefer(on: int) = "lvk_sl_prefer"
 extern function vk_sl_active() -> int = "lvk_sl_active"
 extern function vk_sl_init(pref: pointer, sdk_version: long) -> int = "lsl_slInit"

runtime/native/vk_mac.ll

@@ -250,3 +250,17 @@ push:
   store ptr %p, ptr @lvk_pool
   ret void
 }
+
+; ---- the heap in use --------------------------------------------------------------------------
+; malloc's live bytes across the default zones, for a test that proves a path allocates nothing in
+; its steady state (render3d's examples/rendering/steady.ludic). malloc_statistics_t is four
+; words: blocks_in_use (u32, padded), size_in_use, max_size_in_use, size_allocated.
+declare void @malloc_zone_statistics(ptr, ptr)
+define i64 @lvk_heap_bytes() {
+entry:
+  %st = alloca [4 x i64], align 8
+  call void @malloc_zone_statistics(ptr null, ptr %st)
+  %p = getelementptr [4 x i64], ptr %st, i32 0, i32 1
+  %n = load i64, ptr %p
+  ret i64 %n
+}

runtime/native/vk_win.ll

@@ -369,3 +369,9 @@ define void @lvk_frame_pool() {
 entry:
   ret void
 }
+
+; the heap's live bytes are asked for on the Mac only (vk_mac.ll); 0 here, and a test skips its check
+define i64 @lvk_heap_bytes() {
+entry:
+  ret i64 0
+}