Uncaught (in promise) TypeError: Cannot convert 1623120 to a BigInt When -sEMULATE_FUNCTION_POINTER_CASTS Is Used

[kala7a]

I observe following error when I try to use -sEMULATE_FUNCTION_POINTER_CASTS linker option when building with gst.wasm

Initially I observed it in internal project that was using this flag once we intergrated gst.wasm inside
But issue seems to happen also with gst.wasm examples if we add the flag:
I've put the flag in this example:

diff --git a/gst.wasm/subprojects/samples/codecs/meson.build b/gst.wasm/subprojects/samples/codecs/meson.build
index 23bb276..c744719 100644
--- a/gst.wasm/subprojects/samples/codecs/meson.build
+++ b/gst.wasm/subprojects/samples/codecs/meson.build
@@ -19,7 +19,8 @@ executable(executable_name,
       # This is giving problems when running the WebRunner at set_format (RDI-2850)
       '-sPROXY_TO_PTHREAD',
       '-lGL',
-      '-sOFFSCREENCANVAS_SUPPORT'
+      '-sOFFSCREENCANVAS_SUPPORT',
+      '-sEMULATE_FUNCTION_POINTER_CASTS'
     ],
     name_suffix: 'js',
     install: true,

codecs-example.js:1 Uncaught (in promise) TypeError: Cannot convert 1623120 to a BigInt
    at ffi_call_js (codecs-example.js:1:237206)
    at codecs-example.wasm:0x60e012
    at codecs-example.wasm:0x3603b1
    at codecs-example.wasm:0x60e868
    at codecs-example.wasm:0x367132
    at codecs-example.wasm:0x1eef4
    at codecs-example.wasm:0x23df44
    at codecs-example.wasm:0x533cda
    at codecs-example.wasm:0x380433
    at codecs-example.wasm:0x7e6c7

I see also that this EMULATE_FUNCTION_POINTER_CASTS flag is marked deprecated so I have to analyze how to remove it from our internal project.

But might be also something fixable on gst.wasm side?

[turran]

Hello @kala7a,

As you commented, the flag EMULATE_FUNCTION_POINTER_CASTS is deprecated. I wouldn't use it in new code, not only because of its deprecation status but also because there are plenty of documented errors about its behavior. Internally, it converts all the parameters a function receives/calls into 10 int64-based arguments.

In gst.wasm, we had to manually patch both GLib and GStreamer to avoid casts, especially on the GObject class registration code. At the end, due to the impossibility of upstreaming such changes, we decided to improve LLVM to support the castings at the frontend level (check llvm/llvm-project#153168).

We are currently removing the casting commits we did to simply use the new LLVM. So far, everything is working. I recommend using this new LLVM branch and avoiding the flag.

Let me know how it went out.