[bindings] Use the same SipHash keys to make C++ header stable

Author: TheBlueMatt

.github/workflows/build.yml

@@ -173,15 +173,7 @@ jobs:
             cat lightning-c-bindings/include/lightning.h | grep -v "Generated with cbindgen:[0-9\.]*" | sort > lightning-c-bindings/include/lightning.h.sorted
             cat lightning-c-bindings/include/lightning.h.new | grep -v "Generated with cbindgen:[0-9\.]*" | sort > lightning-c-bindings/include/lightning.h.new.sorted
             diff lightning-c-bindings/include/lightning.h.sorted lightning-c-bindings/include/lightning.h.new.sorted
-            #
-            mv lightning-c-bindings/include/lightningpp.hpp lightning-c-bindings/include/lightningpp.hpp.new
-            git checkout lightning-c-bindings/include/lightningpp.hpp
-            cat lightning-c-bindings/include/lightningpp.hpp | sort > lightning-c-bindings/include/lightningpp.hpp.sorted
-            cat lightning-c-bindings/include/lightningpp.hpp.new | sort > lightning-c-bindings/include/lightningpp.hpp.new.sorted
-            diff lightning-c-bindings/include/lightningpp.hpp.sorted lightning-c-bindings/include/lightningpp.hpp.new.sorted
-            #
             [ "$(diff lightning-c-bindings/include/lightning.h.sorted lightning-c-bindings/include/lightning.h.new.sorted)" != "" ] && exit 2
-            [ "$(diff lightning-c-bindings/include/lightningpp.hpp.sorted lightning-c-bindings/include/lightningpp.hpp.new.sorted)" != "" ] && exit 3
             git diff --exit-code
           fi
 

c-bindings-gen/src/main.rs

@@ -1350,7 +1350,7 @@ fn main() {
 	// ...then walk the ASTs tracking what types we will map, and how, so that we can resolve them
 	// when parsing other file ASTs...
 	let mut libtypes = CrateTypes { traits: HashMap::new(), opaques: HashMap::new(), mirrored_enums: HashMap::new(),
-		type_aliases: HashMap::new(), templates_defined: HashMap::new(), template_file: &mut derived_templates };
+		type_aliases: HashMap::new(), templates_defined: HashMap::default(), template_file: &mut derived_templates };
 	walk_ast(&args[1], "/lib.rs", "".to_string(), &libast, &mut libtypes);
 
 	// ... finally, do the actual file conversion/mapping, writing out types as we go.

c-bindings-gen/src/types.rs

@@ -1,6 +1,7 @@
 use std::collections::HashMap;
 use std::fs::File;
 use std::io::Write;
+use std::hash;
 
 use proc_macro2::{TokenTree, Span};
 
@@ -225,6 +226,13 @@ pub enum DeclType<'a> {
 	EnumIgnored,
 }
 
+// templates_defined is walked to write the C++ header, so if we use the default hashing it get
+// reordered on each genbindings run. Instead, we use SipHasher (which defaults to 0-keys) so that
+// the sorting is stable across runs. It is deprecated, but the "replacement" doesn't actually
+// accomplish the same goals, so we just ignore it.
+#[allow(deprecated)]
+type NonRandomHash = hash::BuildHasherDefault<hash::SipHasher>;
+
 /// Top-level struct tracking everything which has been defined while walking the crate.
 pub struct CrateTypes<'a> {
 	/// This may contain structs or enums, but only when either is mapped as
@@ -240,7 +248,7 @@ pub struct CrateTypes<'a> {
 	/// exists.
 	///
 	/// This is used at the end of processing to make C++ wrapper classes
-	pub templates_defined: HashMap<String, bool>,
+	pub templates_defined: HashMap<String, bool, NonRandomHash>,
 	/// The output file for any created template container types, written to as we find new
 	/// template containers which need to be defined.
 	pub template_file: &'a mut File,