From 209136847e7a382240650febd1452e8f5d77fa5c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tim=20De=CC=81ve=CC=81?= <timdeve@users.noreply.github.com>
Date: Thu, 9 Apr 2020 17:10:43 +0100
Subject: [PATCH] Adds fn Unsafe.leak that prevents destructor from being run
 on a value

---
 src/StartingEnv.hs | 13 ++++++++++++-
 test/unsafe.carp   | 12 ++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)
 create mode 100644 test/unsafe.carp

diff --git a/src/StartingEnv.hs b/src/StartingEnv.hs
index 620cbfae..7c3e465f 100644
--- a/src/StartingEnv.hs
+++ b/src/StartingEnv.hs
@@ -386,7 +386,7 @@ unsafeModule = Env { envBindings = bindings
                    , envUseModules = []
                    , envMode = ExternalEnv
                    , envFunctionNestingLevel = 0 }
-  where bindings = Map.fromList [ templateCoerce ]
+  where bindings = Map.fromList [ templateCoerce, templateLeak ]
 
 -- | A template for coercing (casting) a type to another type
 templateCoerce :: (String, Binder)
@@ -400,6 +400,17 @@ templateCoerce = defineTemplate
                         ,"}"])
   (const [])
 
+-- | A template function for preventing destructor from being run on a value (it's up to the user of this function to make sure that memory is freed).
+templateLeak = defineTemplate
+  (SymPath ["Unsafe"] "leak")
+  (FuncTy [(VarTy "a")] UnitTy StaticLifetimeTy)
+  "prevents a destructor from being run on a value a."
+  (toTemplate "void $NAME ($a a)")
+  (toTemplate $ unlines ["$DECL {"
+                        ,"    // Leak"
+                        ,"}"])
+  (const [])
+
 -- | The global environment before any code is run.
 startingGlobalEnv :: Bool -> Env
 startingGlobalEnv noArray =
diff --git a/test/unsafe.carp b/test/unsafe.carp
new file mode 100644
index 00000000..6e4aba2e
--- /dev/null
+++ b/test/unsafe.carp
@@ -0,0 +1,12 @@
+(load "Test.carp")
+(use Test)
+
+(deftest test
+  (assert-equal test
+                1l
+                (do
+                  (Debug.reset-memory-balance!)
+                  (let [s @"String"]
+                    (Unsafe.leak s))
+                  (Debug.memory-balance))
+                "Unsafe.leak should stop Carp from freeing allocated memory"))