Use panic hooks instead of using catch_unwind

One of the advantages of doing this is that `ParseCallbacks` no longer
needs to implement `UnwindSafe` which means that users can rely on
`RefCell` and `Cell` to extract information from the callbacks.

Users relying on `catch_unwind` can still achieve similar behavior using
`std::thread::spawn`.

Fixes #2147.

bindgen-cli/main.rs

@@ -6,7 +6,6 @@ extern crate env_logger;
 extern crate log;
 
 use std::env;
-use std::panic;
 
 mod options;
 use crate::options::builder_from_flags;
@@ -41,18 +40,18 @@ pub fn main() {
         Ok((builder, output, verbose)) => {
             #[cfg(feature = "logging")]
             clang_version_check();
-            let builder_result = panic::catch_unwind(|| {
-                builder.generate().expect("Unable to generate bindings")
-            });
 
-            if builder_result.is_err() {
+            std::panic::set_hook(Box::new(move |_info| {
                 if verbose {
-                    print_verbose_err();
+                    print_verbose_err()
                 }
-                std::process::exit(1);
-            }
+            }));
+
+            let bindings =
+                builder.generate().expect("Unable to generate bindings");
+
+            let _ = std::panic::take_hook();
 
-            let bindings = builder_result.unwrap();
             bindings.write(output).expect("Unable to write output");
         }
         Err(error) => {

bindgen/callbacks.rs

@@ -5,7 +5,6 @@ pub use crate::ir::derive::CanDerive as ImplementsTrait;
 pub use crate::ir::enum_ty::{EnumVariantCustomBehavior, EnumVariantValue};
 pub use crate::ir::int::IntKind;
 use std::fmt;
-use std::panic::UnwindSafe;
 
 /// An enum to allow ignoring parsing of macros.
 #[derive(Copy, Clone, Debug, PartialEq, Eq)]
@@ -25,7 +24,7 @@ impl Default for MacroParsingBehavior {
 
 /// A trait to allow configuring different kinds of types in different
 /// situations.
-pub trait ParseCallbacks: fmt::Debug + UnwindSafe {
+pub trait ParseCallbacks: fmt::Debug {
     /// This function will be run on every macro that is identified.
     fn will_parse_macro(&self, _name: &str) -> MacroParsingBehavior {
         MacroParsingBehavior::Default

bindgen/lib.rs

@@ -2103,11 +2103,6 @@ struct BindgenOptions {
     merge_extern_blocks: bool,
 }
 
-/// TODO(emilio): This is sort of a lie (see the error message that results from
-/// removing this), but since we don't share references across panic boundaries
-/// it's ok.
-impl ::std::panic::UnwindSafe for BindgenOptions {}
-
 impl BindgenOptions {
     fn build(&mut self) {
         let mut regex_sets = [