don't swallow panics from spawned threads

pgrx-pg-sys/src/submodules/panic.rs

@@ -304,14 +304,23 @@ fn take_panic_location() -> ErrorReportLocation {
 }
 
 pub fn register_pg_guard_panic_hook() {
-    std::panic::set_hook(Box::new(|info| {
-        PANIC_LOCATION.with(|thread_local| {
-            thread_local.replace({
-                let mut info: ErrorReportLocation = info.into();
-                info.backtrace = Some(std::backtrace::Backtrace::capture());
-                Some(info)
-            })
-        });
+    use super::thread_check::is_os_main_thread;
+
+    let default_hook = std::panic::take_hook();
+    std::panic::set_hook(Box::new(move |info: _| {
+        if is_os_main_thread() == Some(true) {
+            // if this is the main thread, swallow the panic message and use postgres' error-reporting mechanism.
+            PANIC_LOCATION.with(|thread_local| {
+                thread_local.replace({
+                    let mut info: ErrorReportLocation = info.into();
+                    info.backtrace = Some(std::backtrace::Backtrace::capture());
+                    Some(info)
+                })
+            });
+        } else {
+            // if this isn't the main thread, we don't know which connection to associate the panic with.
+            default_hook(info)
+        }
     }))
 }
 

pgrx-pg-sys/src/submodules/thread_check.rs

@@ -47,7 +47,7 @@ pub(crate) fn check_active_thread() {
 /// Concretely, it is very important that this not return `Some(false)`
 /// incorrectly, but the other values are less important. Callers generally
 /// should compare the result against `Some(false)`.
-fn is_os_main_thread() -> Option<bool> {
+pub(super) fn is_os_main_thread() -> Option<bool> {
     #[cfg(any(target_os = "macos", target_os = "openbsd", target_os = "freebsd"))]
     return unsafe {
         match libc::pthread_main_np() {
@@ -116,7 +116,7 @@ fn thread_id_check_failed() -> ! {
     // I don't think this can ever happen, but it would be a bug if it could.
     assert_ne!(is_os_main_thread(), Some(true), "`pgrx` active thread is not the main thread!?");
     panic!(
-        "{}:  postgres FFI may not not be called from multiple threads.",
+        "{}:  postgres FFI may not be called from multiple threads.",
         std::panic::Location::caller()
     );
 }