Syntax error! The symbol `JSCheckScriptSyntax' does not fit here.

[panmona]

In my project, I suddenly get the following error when building with GHC, which causes autocomplete (HLS) to completely fail:

Failed to build webkit2gtk3-javascriptcore-0.14.4.6.
Build log (
/home/m/.cabal/logs/ghc-9.12.2/webkit2gtk3-javascriptcore-0.14.4.6-e338888fe8281e79c6394e3e53741a95909fe0ea837ddbb440d6bba2fd75787e.log
):
[1 of 2] Compiling Main             ( dist/setup/setup.hs, dist/setup/Main.o )
[2 of 2] Linking dist/setup/setup
Configuring webkit2gtk3-javascriptcore-0.14.4.6...
Preprocessing library for webkit2gtk3-javascriptcore-0.14.4.6...
setup: Error in C header file.

/usr/include/webkitgtk-4.0/JavaScriptCore/JSBase.h:125: (column 44) [FATAL] 
  >>> Syntax error!
  The symbol `JSCheckScriptSyntax' does not fit here.

I don't have a direct dependency on this package but via reflex-dom.

Versions:

$ ghc --version
The Glorious Glasgow Haskell Compilation System, version 9.12.2
$ cabal --version
cabal-install version 3.14.1.1
compiled using version 3.14.1.1 of the Cabal library 

Let me know if you need any more information.

Discourse topic for reference: https://discourse.haskell.org/t/build-failing-for-ghcjs-project-the-symbol-jscheckscriptsyntax-does-not-fit-here/12185/4

[alexfmpe]

I've built reflex-dom with 9.12 both out of nixpkgs and with cabal many times and webkit2gtk3-javascriptcore comes along for the ride just fine.
Maybe you're building against a different version of the webkitgtk library or so?
I seem to be getting webkitgtk-2.48.2 myself

$ cd nixpkgs

$ git rev-parse HEAD
ee303125183c30e3fb9cf61cc8ea110719939d20

$ nix-build -A webkitgtk_4_0
/nix/store/4dajfxlvzhwxa2sb8bf21j3r9c3gax06-webkitgtk-2.48.2+abi=4.0

$ nix-build -A haskell.packages.ghc912.webkit2gtk3-javascriptcore
/nix/store/xhl49cqq586f52f3jlz1qqly6pjnwcx7-webkit2gtk3-javascriptcore-0.14.4.6

Looking at the source checkout, this symbol seems present in the mentioned line without fuss

$ grep -n "JSCheckScriptSyntax" webkitgtk-2.48.2/Source/JavaScriptCore/API/JSBase.h
116:@function JSCheckScriptSyntax
125:JS_EXPORT bool JSCheckScriptSyntax(JSContextRef ctx, JSStringRef script, JSStringRef sourceURL, int startingLineNumber, JSValueRef* exception);

[panmona]

Thanks for the insights, very appreciated!
A different package version seems like the likely case as I'm currently not using nix. Though I do have 2.48.2 of webkitgtk installed.

[alexfmpe]

Though I do have 2.48.2 of webkitgtk installed.

Huh we must go deeper then
Searching for the "symbol does not fit here" message gives me a few hits, and it seems like a common issue with c2hs https://github.com/haskell/c2hs/issues?q=does%20not%20fit%20here

A good deal of the issues there end up mentioning gcc/glibc versions.
FWIW I seem to always be using gcc 14.2.1 and glibc 2.40.
Maybe also check you have latest c2hs and language-c ?

[panmona]

Something I was wondering is, whether I do need to depend on webkitgtk through reflex-dom or whether I can just use reflex-dom-core. This way this problem would also be fixed. For our development we never need webkitgtk.

In a first try I was unable to get this working with a build through GHC, it is failing at mainWidgetWithHead as main expects IO () and mainWidgetWithHead returns JSM. I also tried to use liftJSM but then I get a No instance for MonadJSM.
I suspect it is not possible to do so?

main :: IO ()
main = do 
  _ <- liftJSM $ mainWidgetWithHead headElement bodyElement
  return ()

---

Regarding the versions:

$ gcc --version
gcc (GCC) 15.1.1 20250425
$ pacman -Ss glibc
core/glibc 2.41+r48+g5cb575ca9a3d-1 [installed]
    GNU C Library
$ pacman -Ss c2hs
extra/c2hs 0.28.8-250
    C->Haskell FFI tool that gives some cross-language type safety

For language-c I am not sure what you refer to? This package here: https://hackage.haskell.org/package/language-c ?

I have different versions of the tools, so I suspect this is the cause...

[alexfmpe]

it is failing at mainWidgetWithHead as main expects IO () and mainWidgetWithHead returns JSM. I also tried to use liftJSM but then I get a No instance for MonadJSM.
I suspect it is not possible to do so?

The reflex-dom package itself has little else than per-platform wrappers of mainWidgetWithHead and friends.
You could mimic this, but you'd end up depending on jsaddle-webkit2gtk directly and be back at the same place.

https://github.com/reflex-frp/reflex-dom/blob/2baa713dfc2e247d1f93380fcab443d9255f2bcb/reflex-dom/src/Reflex/Dom/Internal.hs#L98-L114

I have different versions of the tools, so I suspect this is the cause...

Assuming this is actually the issue, I don't know if it's a version mismatch, if it's something on this repo that needs to change for gcc 15 or something else.

However, if you just want the native backend for dev, HLS, etc, you probably want jsaddle-warp instead and can workaround by setting two flags. See
https://github.com/reflex-frp/reflex-dom/blob/2baa713dfc2e247d1f93380fcab443d9255f2bcb/cabal.project-nogtk#L8-L9

You'd only want jsaddle-webkit2gtk for a native GUI app I think. More details at
https://github.com/ghcjs/jsaddle/?tab=readme-ov-file#how-does-it-work-on-ghc

[panmona]

The reflex-dom package itself has little else than per-platform wrappers of mainWidgetWithHead and friends.
You could mimic this, but you'd end up depending on jsaddle-webkit2gtk directly and be back at the same place.

That makes sense!

However, if you just want the native backend for dev, HLS, etc, you probably want jsaddle-warp instead and can workaround by setting two flags. See

This works, thanks!

I needed to figure out how to exactly specify these flags options and the cabal documentation was unfortunately not as clear as I hoped it would be.
In the end I now needed to create a cabal.project file (I only had a .cabal file before, that is generated with hpack) with the following contents:

packages: .

constraints: reflex-dom +use-warp -webkit2gtk

[alexfmpe]

Huh now that you mention it I wonder if my linked snippet can only be used with local packages