Patches for back porting fixes to 9.12

Author: hamishmack

builder/ghc-for-component-wrapper.nix

@@ -137,9 +137,6 @@ let
   + lib.optionalString (stdenv.hostPlatform.isWasm) ''
      rm $wrappedGhc/lib/*.mjs
      cp $unwrappedGhc/lib/*.mjs $wrappedGhc/lib/
-     substituteInPlace $wrappedGhc/lib/dyld.mjs \
-       --replace-fail "instance.exports.__wasm_apply_data_relocs();" \
-          "if(instance.exports.__wasm_apply_data_relocs) instance.exports.__wasm_apply_data_relocs(); else {}"
   ''
   # Wrap haddock, if the base GHC provides it.
   + ''

overlays/bootstrap.nix

@@ -88,6 +88,7 @@ in {
                 onNative = final.lib.optionals (final.stdenv.buildPlatform == final.stdenv.targetPlatform);
                 onCross = final.lib.optionals (final.stdenv.targetPlatform != final.stdenv.hostPlatform);
                 onGhcjs = final.lib.optionals final.stdenv.targetPlatform.isGhcjs;
+                onWasm = final.lib.optionals final.stdenv.targetPlatform.isWasm;
                 on32bit = final.lib.optionals final.stdenv.targetPlatform.is32bit;
                 # Try to avoid reordering the patches unless a patch is added or changed that
                 # will be applied to most versions of the GHC anyway (reordering the patches
@@ -338,6 +339,9 @@ in {
                 ++ onGhcjs (from        "9.13"         ./patches/ghc/ghc-9.13-ghcjs-rts-types.patch)
 
                 ++ onGhcjs (fromUntil   "9.6.7" "9.7"  ./patches/ghc/ghc-9.6-js-support-this-unit-id-10819.patch)
+
+                ++ onWasm (until                "9.13" ./patches/ghc/ghc-9.12-wasm-shared-libs.patch)
+                ++ onWasm (until                "9.13" ./patches/ghc/ghc-9.12-wasm-keep-cafs.patch)
                 ;
         in ({
             ghc8107 = traceWarnOld "8.10" (final.callPackage ../compiler/ghc {

overlays/patches/ghc/ghc-9.12-wasm-keep-cafs.patch

@@ -0,0 +1,36 @@
+From 10f06163d9adcb3b6e6438f1524faaca3bf6c3b2 Mon Sep 17 00:00:00 2001
+From: Cheng Shao <[email protected]>
+Date: Sat, 23 Aug 2025 05:11:31 +0200
+Subject: [PATCH] wasm: ensure setKeepCAFs() is called in ghci
+
+This patch is a critical bugfix for #26106, see comment and linked
+issue for details.
+---
+ utils/jsffi/dyld.mjs | 14 ++++++++++++++
+ 1 file changed, 14 insertions(+)
+
+diff --git a/utils/jsffi/dyld.mjs b/utils/jsffi/dyld.mjs
+index 285cc8b72011..8c38ebc2efa0 100755
+--- a/utils/jsffi/dyld.mjs
++++ b/utils/jsffi/dyld.mjs
+@@ -1105,6 +1105,20 @@ class DyLD {
+       if (/libHSghc-internal-\d+(\.\d+)*/i.test(soname)) {
+         this.rts_init();
+         delete this.rts_init;
++
++        // At this point the RTS symbols in linear memory are fixed
++        // and constructors are run, especially the one in JSFFI.c
++        // that does GHC RTS initialization for any code that links
++        // JSFFI.o. Luckily no Haskell computation or gc has taken
++        // place yet, so we must set keepCAFs=1 right now! Otherwise,
++        // any BCO created by later TH splice or ghci expression may
++        // refer to any CAF that's not reachable from GC roots (here
++        // our only entry point is defaultServer) and the CAF could
++        // have been GC'ed! (#26106)
++        //
++        // We call it here instead of in RTS C code, since we only
++        // want keepCAFs=1 for ghci, not user code.
++        this.exportFuncs.setKeepCAFs();
+       }
+       init();
+     }

overlays/patches/ghc/ghc-9.12-wasm-shared-libs.patch

@@ -0,0 +1,41 @@
+From cb60da245b2fea7a0c39af0e58f9ef89104a9255 Mon Sep 17 00:00:00 2001
+From: Cheng Shao <[email protected]>
+Date: Fri, 21 Feb 2025 20:30:31 +0000
+Subject: [PATCH] wasm: fix dyld for shared libraries created by llvm 20.x
+
+This patch fixes wasm dyld script for shared libraries created by llvm
+20.x. The __wasm_apply_data_relocs function is now optional and may be
+omitted for shared libraries without any runtime relocatable data
+segments, so only call __wasm_apply_data_relocs when it's present.
+---
+ utils/jsffi/dyld.mjs | 13 +++++++++----
+ 1 file changed, 9 insertions(+), 4 deletions(-)
+
+diff --git a/utils/jsffi/dyld.mjs b/utils/jsffi/dyld.mjs
+index 3c1c2106557a..c6cfedbece4f 100755
+--- a/utils/jsffi/dyld.mjs
++++ b/utils/jsffi/dyld.mjs
+@@ -796,12 +796,17 @@ class DyLD {
+ 
+       const init = () => {
+         // See
+-        // https://github.com/llvm/llvm-project/blob/llvmorg-19.1.1/lld/wasm/Writer.cpp#L1430,
+-        // there's also __wasm_init_memory (not relevant yet, we don't
++        // https://gitlab.haskell.org/haskell-wasm/llvm-project/-/blob/release/20.x/lld/wasm/Writer.cpp#L1450,
++        // __wasm_apply_data_relocs is now optional so only call it if
++        // it exists (we know for sure it exists for libc.so though).
++        // There's also __wasm_init_memory (not relevant yet, we don't
+         // use passive segments) & __wasm_apply_global_relocs but
+         // those are included in the start function and should have
+-        // been called upon instantiation.
+-        instance.exports.__wasm_apply_data_relocs();
++        // been called upon instantiation, see
++        // Writer::createStartFunction().
++        if (instance.exports.__wasm_apply_data_relocs) {
++          instance.exports.__wasm_apply_data_relocs();
++        }
+ 
+         instance.exports._initialize();
+       };
+-- 
+GitLab