failed to construct C string from string for gl proc address

Error message

failed to construct C string from string for gl proc address

What it means

Error "failed to construct C string from string for gl proc address" thrown in emilk/egui.

Solutions

A GL function name contained an interior NUL byte: strip NUL characters before constructing the C string for the proc address lookup.

Example fix

let cname = std::ffi::CString::new(name.replace('\0', "")).expect("valid gl symbol name");

When it happens

Trigger: Thrown at crates/eframe/src/native/glow_integration.rs:227 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of emilk/egui@8fb03c9ae9 (2026-08-19). Data as JSON: /api/errors/c7266050ca52f3f3. Report an issue: GitHub.

Appendix: source

Thrown at crates/eframe/src/native/glow_integration.rs:227

        let mut glutin_window_context = unsafe {
            GlutinWindowContext::new(egui_ctx, winit_window_builder, native_options, event_loop)?
        };

        // Creates the window - must come before we create our glow context
        glutin_window_context.initialize_window(ViewportId::ROOT, event_loop)?;

        {
            let viewport = &glutin_window_context.viewports[&ViewportId::ROOT];
            let window = viewport.window.as_ref().unwrap(); // Can't fail - we just called `initialize_all_viewports`
            epi_integration::apply_window_settings(window, window_settings);
        }

        let gl = unsafe {
            profiling::scope!("glow::Context::from_loader_function");
            Arc::new(glow::Context::from_loader_function(|s| {
                let s = std::ffi::CString::new(s)
                    .expect("failed to construct C string from string for gl proc address");

                glutin_window_context.get_proc_address(&s)
            }))
        };

        let painter = egui_glow::Painter::new(
            gl,
            "",
            native_options.glow_options.shader_version,
            native_options.dithering,
        )?;

        Ok((glutin_window_context, painter))
    }

    fn init_run_state(
        &mut self,
        event_loop: &ActiveEventLoop,

View on GitHub (pinned to 8fb03c9ae9)