gfx-rs/wgpu · error

Only available on WebGPU

Error message

Only available on WebGPU

What it means

Panic in the core buffer-mapped-range's as_uint8array: this method only exists to serve the WebGPU (browser) backend, where mapped memory is a JS Uint8Array; on a native core buffer there is no such array to return, so the trait method is an unreachable stub.

Source

Thrown at wgpu/src/backend/wgpu_core.rs:2844

impl dispatch::BufferMappedRangeInterface for CoreBufferMappedRange {
    #[inline]
    fn len(&self) -> usize {
        self.size
    }

    #[inline]
    unsafe fn read_slice(&self) -> &[u8] {
        unsafe { slice::from_raw_parts(self.ptr.as_ptr(), self.size) }
    }

    #[inline]
    unsafe fn write_slice(&mut self) -> WriteOnly<'_, [u8]> {
        unsafe { WriteOnly::new(NonNull::slice_from_raw_parts(self.ptr, self.size)) }
    }

    #[cfg(webgpu)]
    fn as_uint8array(&self) -> &js_sys::Uint8Array {
        panic!("Only available on WebGPU")
    }
}

View on GitHub (pinned to 3e11ff59bf)

Solutions

1. Use read_slice()/write_slice() to access native mapped memory instead of as_uint8array
2. Only call as_uint8array behind a webgpu backend check

When it happens

Trigger: Thrown at wgpu/src/backend/wgpu_core.rs:2844 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of gfx-rs/wgpu@3e11ff59bf (2026-09-03). Data as JSON: /api/errors/7730b5a8c6104912. Report an issue: GitHub.