[bindings] Allow cloning opaque types when inner is NULL

Previously we'd segfault trying to deref the NULL page, but there
is no reason to not simply clone by creating another opaque instance
with a null inner. This comes up specifically when cloning
ChannelSigners as the pubkeys instance is NULL on construction
before get_pubkeys is called.

diff --git a/c-bindings-gen/src/main.rs b/c-bindings-gen/src/main.rs
index d927d2ae71c816af9f92ee824861103715117d0f..97fc9b8731849df13ddfe041755c6c85e7c39058 100644 (file)
--- a/c-bindings-gen/src/main.rs
+++ b/c-bindings-gen/src/main.rs
@@ -559,7 +559,8 @@ fn writeln_opaque<W: std::io::Write>(w: &mut W, ident: &syn::Ident, struct_name:
                writeln!(w, "impl Clone for {} {{", struct_name).unwrap();
                writeln!(w, "\tfn clone(&self) -> Self {{").unwrap();
                writeln!(w, "\t\tSelf {{").unwrap();
-               writeln!(w, "\t\t\tinner: Box::into_raw(Box::new(unsafe {{ &*self.inner }}.clone())),").unwrap();
+               writeln!(w, "\t\t\tinner: if self.inner.is_null() {{ std::ptr::null_mut() }} else {{").unwrap();
+               writeln!(w, "\t\t\t\tBox::into_raw(Box::new(unsafe {{ &*self.inner }}.clone())) }},").unwrap();
                writeln!(w, "\t\t\tis_owned: true,").unwrap();
                writeln!(w, "\t\t}}\n\t}}\n}}").unwrap();
                writeln!(w, "#[allow(unused)]").unwrap();
@@ -569,7 +570,7 @@ fn writeln_opaque<W: std::io::Write>(w: &mut W, ident: &syn::Ident, struct_name:
                writeln!(w, "}}").unwrap();
                writeln!(w, "#[no_mangle]").unwrap();
                writeln!(w, "pub extern \"C\" fn {}_clone(orig: &{}) -> {} {{", struct_name, struct_name, struct_name).unwrap();
-               writeln!(w, "\t{} {{ inner: Box::into_raw(Box::new(unsafe {{ &*orig.inner }}.clone())), is_owned: true }}", struct_name).unwrap();
+               writeln!(w, "\torig.clone()").unwrap();
                writeln!(w, "}}").unwrap();
        }