From 359e09f7cd4093bf9c49a47f859bdaeae4697ec9 Mon Sep 17 00:00:00 2001
From: Mike Mueller <mike.mueller@cstudio.ch>
Date: Wed, 6 May 2026 21:21:01 +0200
Subject: [PATCH] Implement panic logging for better debugging

---
 src/common.rs  | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++
 src/service.rs |  1 +
 2 files changed, 65 insertions(+)

diff --git a/src/common.rs b/src/common.rs
index 0b0b8bebf..e71615b24 100644
--- a/src/common.rs
+++ b/src/common.rs
@@ -122,6 +122,7 @@ impl Drop for SimpleCallOnReturn {
 }
 
 pub fn global_init() -> bool {
+    install_panic_hook();
     #[cfg(target_os = "linux")]
     {
         if !crate::platform::linux::is_x11() {
@@ -131,6 +132,69 @@ pub fn global_init() -> bool {
     true
 }
 
+/// Capture Rust panics so they survive the windows-subsystem build.
+///
+/// In release we have `panic = 'abort'` and `windows_subsystem = "windows"`,
+/// which means a panic prints to stderr (which is null when no console is
+/// attached) and immediately calls `abort()`. The flexi_logger file never
+/// sees the panic, and on Windows the abort doesn't reliably surface in the
+/// Application event log either, so the process appears to vanish.
+///
+/// This hook routes every panic to two places before the abort:
+/// 1. `log::error!` — works once `init_log` has set up flexi_logger.
+/// 2. `Config::log_path()/panic.log` — fallback for panics that fire before
+///    `init_log` runs (e.g. inside `load_custom_client` or `bootstrap`).
+///    The log dir is per-user/per-app on every platform and is writable by
+///    the user-session `--server` process; the install dir is not.
+fn install_panic_hook() {
+    use std::sync::Once;
+    static INIT: Once = Once::new();
+    INIT.call_once(|| {
+        let prev = std::panic::take_hook();
+        std::panic::set_hook(Box::new(move |info| {
+            let payload: &str = if let Some(s) = info.payload().downcast_ref::<&'static str>() {
+                s
+            } else if let Some(s) = info.payload().downcast_ref::<String>() {
+                s.as_str()
+            } else {
+                "<non-string panic payload>"
+            };
+            let location = info
+                .location()
+                .map(|l| format!("{}:{}:{}", l.file(), l.line(), l.column()))
+                .unwrap_or_else(|| "<unknown>".into());
+            let backtrace = std::backtrace::Backtrace::force_capture();
+            let exe = std::env::current_exe()
+                .ok()
+                .and_then(|p| p.to_str().map(|s| s.to_owned()))
+                .unwrap_or_default();
+            let pid = std::process::id();
+            let args: Vec<String> = std::env::args().collect();
+            let header = format!(
+                "PANIC pid={pid} exe={exe} args={args:?}\n  at {location}\n  payload: {payload}"
+            );
+            log::error!("{header}\n  backtrace:\n{backtrace}");
+            let mut path = config::Config::log_path();
+            let _ = std::fs::create_dir_all(&path);
+            path.push("panic.log");
+            if let Ok(mut f) = std::fs::OpenOptions::new()
+                .create(true)
+                .append(true)
+                .open(&path)
+            {
+                use std::io::Write;
+                let ts = std::time::SystemTime::now()
+                    .duration_since(std::time::UNIX_EPOCH)
+                    .map(|d| d.as_secs())
+                    .unwrap_or(0);
+                let _ = writeln!(f, "[unix={ts}] {header}\n  backtrace:\n{backtrace}\n");
+                let _ = f.flush();
+            }
+            prev(info);
+        }));
+    });
+}
+
 pub fn global_clean() {}
 
 #[inline]
diff --git a/src/service.rs b/src/service.rs
index ce1855bdb..4a3c82430 100644
--- a/src/service.rs
+++ b/src/service.rs
@@ -5,6 +5,7 @@ fn main() {}
 
 #[cfg(target_os = "macos")]
 fn main() {
+    crate::common::global_init();
     crate::common::load_custom_client();
     hbb_common::init_log(false, "service");
     crate::start_os_service();