wasilibc: 19 -> 20

pkgsCross.wasi32.llvmPackages: 12 -> 16

* It appears BULK_MEMORY_SOURCES no longer needs to be set to be empty
  to compile firefox. Without it, the build of wasilibc would fail if
  enableThreads is true.

* Include preliminary support for the experimental threads support in
  wasilibc which provides pthreads API. If wasilibc is built with
  support, is exposed via passthru and libcxx / libcxxabi are built with
  threads support accordingly.

  See also:
  - WebAssembly/wasi-sdk#274
  - WebAssembly/wasi-sdk#301
  - WebAssembly/wasi-sdk#314

  wasi-sdk ships it by default, but as a separate variant of libc which
  would be a hassle for us. Let's just make it optional for now.

  You can try it out using the following overlay:

      self: super: {
        wasilibc = super.wasilibc.override { enableThreads = true; };
      }

  Flags for libc++abi are copied from wasi-sdk.

pkgs/development/compilers/llvm/16/libcxx/default.nix

@@ -79,7 +79,7 @@ stdenv.mkDerivation rec {
     ++ lib.optional (stdenv.hostPlatform.isMusl || stdenv.hostPlatform.isWasi) "-DLIBCXX_HAS_MUSL_LIBC=1"
     ++ lib.optional (stdenv.hostPlatform.useLLVM or false) "-DLIBCXX_USE_COMPILER_RT=ON"
     ++ lib.optionals stdenv.hostPlatform.isWasm [
-      "-DLIBCXX_ENABLE_THREADS=OFF"
+      "-DLIBCXX_ENABLE_THREADS=${if stdenv.cc.libc.hasThreads then "ON" else "OFF"}"
       "-DLIBCXX_ENABLE_FILESYSTEM=OFF"
       "-DLIBCXX_ENABLE_EXCEPTIONS=OFF"
     ] ++ lib.optional (!enableShared) "-DLIBCXX_ENABLE_SHARED=OFF"

pkgs/development/compilers/llvm/16/libcxxabi/default.nix

@@ -69,10 +69,26 @@ stdenv.mkDerivation rec {
   ] ++ lib.optionals (stdenv.hostPlatform.useLLVM or false) [
     "-DLLVM_ENABLE_LIBCXX=ON"
     "-DLIBCXXABI_USE_LLVM_UNWINDER=ON"
-  ] ++ lib.optionals stdenv.hostPlatform.isWasm [
-    "-DLIBCXXABI_ENABLE_THREADS=OFF"
-    "-DLIBCXXABI_ENABLE_EXCEPTIONS=OFF"
-  ] ++ lib.optionals (!enableShared) [
+  ] ++ lib.optionals stdenv.hostPlatform.isWasm (
+    [
+      "-DLIBCXXABI_ENABLE_EXCEPTIONS=OFF"
+      # CMake tests for -fno-exceptions together with -lc++ -lc++abi which fails
+      # here, without -fno-exceptions, libc++abi is unusable later.
+      # See also: https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=260005
+      # TODO(@sternenseemann): make this unconditional?
+      "-DCXX_SUPPORTS_FNO_EXCEPTIONS_FLAG=ON"
+    ]
+    ++ (if stdenv.cc.libc.hasThreads then [
+      "-DLIBCXXABI_ENABLE_THREADS=ON"
+      "-DLIBCXXABI_HAS_PTHREAD_API=ON"
+      "-DLIBCXXABI_HAS_EXTERNAL_THREAD_API=OFF"
+      "-DLIBCXXABI_BUILD_EXTERNAL_THREAD_LIBRARY=OFF"
+      "-DLIBCXXABI_HAS_WIN32_THREAD_API=OFF"
+    ] else [
+      "-DLIBCXXABI_ENABLE_THREADS=OFF"
+    ])
+  )
+  ++ lib.optionals (!enableShared) [
     "-DLIBCXXABI_ENABLE_SHARED=OFF"
   ];
 

pkgs/development/libraries/wasilibc/default.nix

@@ -2,13 +2,16 @@
 , buildPackages
 , fetchFromGitHub
 , lib
+# Enable experimental wasilibc pthread support
+, enableThreads ? false
+# For tests
 , firefox-unwrapped
 , firefox-esr-unwrapped
 }:
 
 let
   pname = "wasilibc";
-  version = "19";
+  version = "20";
 in
 stdenv.mkDerivation {
   inherit pname version;
@@ -17,7 +20,7 @@ stdenv.mkDerivation {
     owner = "WebAssembly";
     repo = "wasi-libc";
     rev = "refs/tags/wasi-sdk-${version}";
-    hash = "sha256-yQSKoSil/C/1lIHwEO9eQKC/ye3PJIFGYjHyNDn61y4=";
+    sha256 = "0knm5ch499dksmv1k0kh7356pjd9n1gjn0p3vp9bw57mn478zp8z";
     fetchSubmodules = true;
   };
 
@@ -38,8 +41,7 @@ stdenv.mkDerivation {
       "SYSROOT_LIB:=$SYSROOT_LIB"
       "SYSROOT_INC:=$SYSROOT_INC"
       "SYSROOT_SHARE:=$SYSROOT_SHARE"
-      # https://bugzilla.mozilla.org/show_bug.cgi?id=1773200
-      "BULK_MEMORY_SOURCES:="
+      "THREAD_MODEL=${if enableThreads then "posix" else "single"}"
     )
 
   '';
@@ -53,8 +55,11 @@ stdenv.mkDerivation {
     ln -s $share/share/undefined-symbols.txt $out/lib/wasi.imports
   '';
 
-  passthru.tests = {
-    inherit firefox-unwrapped firefox-esr-unwrapped;
+  passthru = {
+    tests = {
+      inherit firefox-unwrapped firefox-esr-unwrapped;
+    };
+    hasThreads = enableThreads;
   };
 
   meta = with lib; {

pkgs/top-level/all-packages.nix

@@ -16125,7 +16125,7 @@ with pkgs;
       else if platform.isFreeBSD then 12
       else if platform.isAndroid then 12
       else if platform.isLinux then 11
-      else if platform.isWasm then 12
+      else if platform.isWasm then 16
       else 14;
     # We take the "max of the mins". Why? Since those are lower bounds of the
     # supported version set, this is like intersecting those sets and then