[Git][ghc/ghc][wip/wasm-prim-improve] 2 commits: wasm: make JSVal internal Weak# point to lifted JSVal
Cheng Shao (@TerrorJack)
gitlab at gitlab.haskell.org
Tue Mar 4 14:38:22 UTC 2025
Cheng Shao pushed to branch wip/wasm-prim-improve at Glasgow Haskell Compiler / GHC
Commits:
b232796c by Cheng Shao at 2025-03-04T14:35:55+00:00
wasm: make JSVal internal Weak# point to lifted JSVal
JSVal has an internal Weak# with the unlifted JSVal# object as key to
arrange its builtin finalization logic. The Weak# used to designate
Unit_closure as a dummy value; now this commit designates the lifted
JSVal closure as the Weak# value. This allows the implementation of
mkWeakJSVal which can be used to observe the liveliness of a JSVal and
attach a user-specified finalizer.
- - - - -
c5fb34e2 by Cheng Shao at 2025-03-04T14:36:45+00:00
ghc-experimental: add mkWeakJSVal
This commit adds a mkWeakJSVal function that can be used to set up a
Weak pointer with a JSVal key to observe the key's lifetime and
optionally attach a finalizer.
- - - - -
5 changed files:
- libraries/ghc-experimental/src/GHC/Wasm/Prim.hs
- libraries/ghc-internal/src/GHC/Internal/Wasm/Prim.hs
- libraries/ghc-internal/src/GHC/Internal/Wasm/Prim/Types.hs
- rts/wasm/JSFFI.c
- testsuite/tests/jsffi/jsffigc.hs
Changes:
=====================================
libraries/ghc-experimental/src/GHC/Wasm/Prim.hs
=====================================
@@ -4,6 +4,7 @@ module GHC.Wasm.Prim (
-- User-facing JSVal type and freeJSVal
JSVal,
freeJSVal,
+ mkWeakJSVal,
-- The JSString type and conversion from/to Haskell String
JSString (..),
=====================================
libraries/ghc-internal/src/GHC/Internal/Wasm/Prim.hs
=====================================
@@ -4,6 +4,7 @@ module GHC.Internal.Wasm.Prim (
-- User-facing JSVal type and freeJSVal
JSVal (..),
freeJSVal,
+ mkWeakJSVal,
-- The JSString type and conversion from/to Haskell String
JSString (..),
=====================================
libraries/ghc-internal/src/GHC/Internal/Wasm/Prim/Types.hs
=====================================
@@ -8,6 +8,7 @@ module GHC.Internal.Wasm.Prim.Types (
JSVal# (..),
JSVal (..),
freeJSVal,
+ mkWeakJSVal,
JSString (..),
fromJSString,
toJSString,
@@ -26,6 +27,7 @@ import GHC.Internal.IO.Encoding
import GHC.Internal.Num
import GHC.Internal.Show
import GHC.Internal.Stable
+import GHC.Internal.Weak
{-
@@ -82,7 +84,7 @@ newtype JSVal#
= JSVal# (Any :: UnliftedType)
data JSVal
- = forall a . JSVal JSVal# (Weak# JSVal#) (StablePtr# a)
+ = forall a . JSVal JSVal# (Weak# JSVal) (StablePtr# a)
freeJSVal :: JSVal -> IO ()
freeJSVal v@(JSVal _ w sp) = do
@@ -94,6 +96,12 @@ freeJSVal v@(JSVal _ w sp) = do
IO $ \s0 -> case finalizeWeak# w s0 of
(# s1, _, _ #) -> (# s1, () #)
+mkWeakJSVal :: JSVal -> Maybe (IO ()) -> IO (Weak JSVal)
+mkWeakJSVal v@(JSVal k _ _) (Just (IO fin)) = IO $ \s0 ->
+ case mkWeak# k v fin s0 of
+ (# s1, w #) -> (# s1, Weak w #)
+mkWeakJSVal (JSVal _ w _) Nothing = pure $ Weak w
+
foreign import javascript unsafe "if (!__ghc_wasm_jsffi_finalization_registry.unregister($1)) { throw new WebAssembly.RuntimeError('js_callback_unregister'); }"
js_callback_unregister :: JSVal -> IO ()
=====================================
rts/wasm/JSFFI.c
=====================================
@@ -107,7 +107,6 @@ HaskellObj rts_mkJSVal(Capability *cap, HsJSVal v) {
SET_HDR(w, &stg_WEAK_info, CCS_SYSTEM);
w->cfinalizers = (StgClosure *)cfin;
w->key = p;
- w->value = Unit_closure;
w->finalizer = &stg_NO_FINALIZER_closure;
w->link = cap->weak_ptr_list_hd;
cap->weak_ptr_list_hd = w;
@@ -120,7 +119,9 @@ HaskellObj rts_mkJSVal(Capability *cap, HsJSVal v) {
box->payload[0] = p;
box->payload[1] = (HaskellObj)w;
box->payload[2] = NULL;
- return TAG_CLOSURE(1, box);
+
+ w->value = TAG_CLOSURE(1, box);
+ return w->value;
}
__attribute__((import_module("ghc_wasm_jsffi"), import_name("getJSVal")))
=====================================
testsuite/tests/jsffi/jsffigc.hs
=====================================
@@ -4,7 +4,7 @@ module Test where
import Data.Maybe
import GHC.Exts
-import GHC.Internal.Wasm.Prim
+import GHC.Wasm.Prim
import GHC.Weak
import System.Mem
@@ -22,13 +22,6 @@ foreign import javascript "wrapper"
foreign export javascript "testDynExportFree sync"
testDynExportFree :: Int -> Int -> Int -> IO ()
--- JSVal uses Weak# under the hood for garbage collection support,
--- this exposes the internal Weak# to observe the liveliness of
--- JSVal#. Do not use this in your own codebase since this is purely
--- an implementation detail of JSVal and subject to change!
-jsvalWeak :: JSVal -> Weak JSVal
-jsvalWeak (JSVal _ w _) = Weak $ unsafeCoerce# Weak w
-
probeWeak :: Weak v -> IO ()
probeWeak wk = print =<< isJust <$> deRefWeak wk
@@ -42,7 +35,7 @@ testDynExportFree x y z = do
-- wk_js observe the liveliness of the JavaScript callback on the
-- Haskell heap. Make sure it's eagerly evaluated and isn't a thunk
-- that retains cb.
- let !wk_js = jsvalWeak cb
+ !wk_js <- mkWeakJSVal cb Nothing
print $ js_to_hs cb x y
-- Eagerly drop references to both the JavaScript callback and the
-- Haskell function closure.
@@ -60,7 +53,7 @@ testDynExportGC x y z = do
let fn a b = a * b + z
wk_fn <- mkWeak fn () Nothing
cb <- js_from_hs fn
- let !wk_js = jsvalWeak cb
+ !wk_js <- mkWeakJSVal cb Nothing
print $ js_to_hs cb x y
-- Why performGC twice? The first run gathers some C finalizers
-- which will be invoked in the second run to free the JSVal
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/b9c27390d828250dc836333ac8fd7ae57ff00861...c5fb34e2cb46a5387b7f0766c4e845febd1a9917
--
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/compare/b9c27390d828250dc836333ac8fd7ae57ff00861...c5fb34e2cb46a5387b7f0766c4e845febd1a9917
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