From: Matt Corallo Date: Sun, 30 May 2021 16:17:25 +0000 (+0000) Subject: Add an export tag to indicate users cannot implement a given trait X-Git-Tag: v0.0.98~5^2~6 X-Git-Url: http://git.bitcoin.ninja/index.cgi?a=commitdiff_plain;h=abc2e0d8b1b385b820387da354bfe3694d433bb2;p=ldk-c-bindings Add an export tag to indicate users cannot implement a given trait Specifically, for the LDK `EventsProvider` trait, we can't (trivially) implement the `process_pending_events` function, defined as: `fn process_pending_events(&self, handler: H) where H::Target: EventHandler;` We currently do not support implementing generic methods, as we'd need to wrap them in a generic Rust-trait-to-C-trait conversion utility, which we do not currently have. Thus, because users almost certainly have no reason to implement the `EventsProvider` themselves, its simpler to simply prevent the use of the C trait struct as the Rust trait. Concretely, this means just skipping the `impl rustEventsProvider for CEventsProvider` block, which works fine as no Rust functions take an `EventsProvider` as an argument. --- diff --git a/c-bindings-gen/src/main.rs b/c-bindings-gen/src/main.rs index 94d25e8..4d0bf58 100644 --- a/c-bindings-gen/src/main.rs +++ b/c-bindings-gen/src/main.rs @@ -221,8 +221,10 @@ macro_rules! walk_supertraits { ($t: expr, $types: expr, ($( $($pat: pat)|* => $ /// a concrete Deref to the Rust trait. fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, types: &mut TypeResolver<'b, 'a>, extra_headers: &mut File, cpp_headers: &mut File) { let trait_name = format!("{}", t.ident); + let implementable; match export_status(&t.attrs) { - ExportStatus::Export => {}, + ExportStatus::Export => { implementable = true; } + ExportStatus::NotImplementable => { implementable = false; }, ExportStatus::NoExport|ExportStatus::TestOnly => return, } writeln_docs(w, &t.attrs, ""); @@ -247,6 +249,7 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty }, ExportStatus::Export => {}, ExportStatus::TestOnly => continue, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } if m.default.is_some() { unimplemented!(); } @@ -505,15 +508,17 @@ fn writeln_trait<'a, 'b, W: std::io::Write>(w: &mut W, t: &'a syn::ItemTrait, ty // Finally, implement the original Rust trait for the newly created mapped trait. writeln!(w, "\nuse {}::{} as rust{};", types.module_path, t.ident, trait_name).unwrap(); - write!(w, "impl rust{}", t.ident).unwrap(); - maybe_write_generics(w, &t.generics, types, false); - writeln!(w, " for {} {{", trait_name).unwrap(); - impl_trait_for_c!(t, "", types); - writeln!(w, "}}\n").unwrap(); - writeln!(w, "// We're essentially a pointer already, or at least a set of pointers, so allow us to be used").unwrap(); - writeln!(w, "// directly as a Deref trait in higher-level structs:").unwrap(); - writeln!(w, "impl std::ops::Deref for {} {{\n\ttype Target = Self;", trait_name).unwrap(); - writeln!(w, "\tfn deref(&self) -> &Self {{\n\t\tself\n\t}}\n}}").unwrap(); + if implementable { + write!(w, "impl rust{}", t.ident).unwrap(); + maybe_write_generics(w, &t.generics, types, false); + writeln!(w, " for {} {{", trait_name).unwrap(); + impl_trait_for_c!(t, "", types); + writeln!(w, "}}\n").unwrap(); + writeln!(w, "// We're essentially a pointer already, or at least a set of pointers, so allow us to be used").unwrap(); + writeln!(w, "// directly as a Deref trait in higher-level structs:").unwrap(); + writeln!(w, "impl std::ops::Deref for {} {{\n\ttype Target = Self;", trait_name).unwrap(); + writeln!(w, "\tfn deref(&self) -> &Self {{\n\t\tself\n\t}}\n}}").unwrap(); + } writeln!(w, "/// Calls the free function if one is set").unwrap(); writeln!(w, "#[no_mangle]\npub extern \"C\" fn {}_free(this_ptr: {}) {{ }}", trait_name, trait_name).unwrap(); @@ -597,6 +602,7 @@ fn writeln_struct<'a, 'b, W: std::io::Write>(w: &mut W, s: &'a syn::ItemStruct, all_fields_settable = false; continue }, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } if let Some(ident) = &field.ident { @@ -675,6 +681,7 @@ fn writeln_impl(w: &mut W, i: &syn::ItemImpl, types: &mut Typ match export_status(&i.attrs) { ExportStatus::Export => {}, ExportStatus::NoExport|ExportStatus::TestOnly => return, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } if let syn::Type::Tuple(_) = &*i.self_ty { @@ -739,7 +746,7 @@ fn writeln_impl(w: &mut W, i: &syn::ItemImpl, types: &mut Typ let export = export_status(&trait_obj.attrs); match export { - ExportStatus::Export => {}, + ExportStatus::Export|ExportStatus::NotImplementable => {}, ExportStatus::NoExport|ExportStatus::TestOnly => return, } @@ -776,6 +783,7 @@ fn writeln_impl(w: &mut W, i: &syn::ItemImpl, types: &mut Typ continue; }, ExportStatus::TestOnly => continue, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } let mut printed = false; @@ -843,6 +851,7 @@ fn writeln_impl(w: &mut W, i: &syn::ItemImpl, types: &mut Typ match export_status(&trait_method.attrs) { ExportStatus::Export => {}, ExportStatus::NoExport|ExportStatus::TestOnly => continue, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } if let syn::ReturnType::Type(_, _) = &$m.sig.output { @@ -1006,6 +1015,7 @@ fn writeln_impl(w: &mut W, i: &syn::ItemImpl, types: &mut Typ match export_status(&m.attrs) { ExportStatus::Export => {}, ExportStatus::NoExport|ExportStatus::TestOnly => continue, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } if m.defaultness.is_some() { unimplemented!(); } writeln_docs(w, &m.attrs, ""); @@ -1128,6 +1138,7 @@ fn writeln_enum<'a, 'b, W: std::io::Write>(w: &mut W, e: &'a syn::ItemEnum, type match export_status(&e.attrs) { ExportStatus::Export => {}, ExportStatus::NoExport|ExportStatus::TestOnly => return, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } if is_enum_opaque(e) { @@ -1328,6 +1339,7 @@ fn writeln_fn<'a, 'b, W: std::io::Write>(w: &mut W, f: &'a syn::ItemFn, types: & match export_status(&f.attrs) { ExportStatus::Export => {}, ExportStatus::NoExport|ExportStatus::TestOnly => return, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } writeln_docs(w, &f.attrs, ""); @@ -1481,6 +1493,7 @@ fn convert_file<'a, 'b>(libast: &'a FullLibraryAST, crate_types: &CrateTypes<'a> match export_status(&t.attrs) { ExportStatus::Export => {}, ExportStatus::NoExport|ExportStatus::TestOnly => continue, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } let mut process_alias = true; @@ -1552,6 +1565,7 @@ fn walk_ast<'a>(ast_storage: &'a FullLibraryAST, crate_types: &mut CrateTypes<'a match export_status(&s.attrs) { ExportStatus::Export => {}, ExportStatus::NoExport|ExportStatus::TestOnly => continue, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } let struct_path = format!("{}::{}", module, s.ident); crate_types.opaques.insert(struct_path, &s.ident); @@ -1560,7 +1574,7 @@ fn walk_ast<'a>(ast_storage: &'a FullLibraryAST, crate_types: &mut CrateTypes<'a syn::Item::Trait(t) => { if let syn::Visibility::Public(_) = t.vis { match export_status(&t.attrs) { - ExportStatus::Export => {}, + ExportStatus::Export|ExportStatus::NotImplementable => {}, ExportStatus::NoExport|ExportStatus::TestOnly => continue, } let trait_path = format!("{}::{}", module, t.ident); @@ -1578,6 +1592,7 @@ fn walk_ast<'a>(ast_storage: &'a FullLibraryAST, crate_types: &mut CrateTypes<'a match export_status(&t.attrs) { ExportStatus::Export => {}, ExportStatus::NoExport|ExportStatus::TestOnly => continue, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } let type_path = format!("{}::{}", module, t.ident); let mut process_alias = true; @@ -1612,6 +1627,7 @@ fn walk_ast<'a>(ast_storage: &'a FullLibraryAST, crate_types: &mut CrateTypes<'a match export_status(&e.attrs) { ExportStatus::Export => {}, ExportStatus::NoExport|ExportStatus::TestOnly => continue, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } let enum_path = format!("{}::{}", module, e.ident); crate_types.opaques.insert(enum_path, &e.ident); @@ -1622,6 +1638,7 @@ fn walk_ast<'a>(ast_storage: &'a FullLibraryAST, crate_types: &mut CrateTypes<'a match export_status(&e.attrs) { ExportStatus::Export => {}, ExportStatus::NoExport|ExportStatus::TestOnly => continue, + ExportStatus::NotImplementable => panic!("(C-not implementable) must only appear on traits"), } let enum_path = format!("{}::{}", module, e.ident); crate_types.mirrored_enums.insert(enum_path, &e); diff --git a/c-bindings-gen/src/types.rs b/c-bindings-gen/src/types.rs index 740e8bd..26a0885 100644 --- a/c-bindings-gen/src/types.rs +++ b/c-bindings-gen/src/types.rs @@ -66,6 +66,11 @@ pub enum ExportStatus { Export, NoExport, TestOnly, + /// This is used only for traits to indicate that users should not be able to implement their + /// own version of a trait, but we should export Rust implementations of the trait (and the + /// trait itself). + /// Concretly, this means that we do not implement the Rust trait for the C trait struct. + NotImplementable, } /// Gets the ExportStatus of an object (struct, fn, etc) given its attributes. pub fn export_status(attrs: &[syn::Attribute]) -> ExportStatus { @@ -117,6 +122,8 @@ pub fn export_status(attrs: &[syn::Attribute]) -> ExportStatus { let line = format!("{}", lit); if line.contains("(C-not exported)") { return ExportStatus::NoExport; + } else if line.contains("(C-not implementable)") { + return ExportStatus::NotImplementable; } }, _ => unimplemented!(), @@ -138,6 +145,7 @@ pub fn is_enum_opaque(e: &syn::ItemEnum) -> bool { for field in fields.named.iter() { match export_status(&field.attrs) { ExportStatus::Export|ExportStatus::TestOnly => {}, + ExportStatus::NotImplementable => panic!("(C-not implementable) should only appear on traits!"), ExportStatus::NoExport => return true, } } @@ -145,6 +153,7 @@ pub fn is_enum_opaque(e: &syn::ItemEnum) -> bool { for field in fields.unnamed.iter() { match export_status(&field.attrs) { ExportStatus::Export|ExportStatus::TestOnly => {}, + ExportStatus::NotImplementable => panic!("(C-not implementable) should only appear on traits!"), ExportStatus::NoExport => return true, } } @@ -479,6 +488,7 @@ impl<'mod_lifetime, 'crate_lft: 'mod_lifetime> ImportResolver<'mod_lifetime, 'cr ExportStatus::Export => { declared.insert(s.ident.clone(), DeclType::StructImported); }, ExportStatus::NoExport => { declared.insert(s.ident.clone(), DeclType::StructIgnored); }, ExportStatus::TestOnly => continue, + ExportStatus::NotImplementable => panic!("(C-not implementable) should only appear on traits!"), } } }, @@ -499,13 +509,19 @@ impl<'mod_lifetime, 'crate_lft: 'mod_lifetime> ImportResolver<'mod_lifetime, 'cr match export_status(&e.attrs) { ExportStatus::Export if is_enum_opaque(e) => { declared.insert(e.ident.clone(), DeclType::EnumIgnored); }, ExportStatus::Export => { declared.insert(e.ident.clone(), DeclType::MirroredEnum); }, + ExportStatus::NotImplementable => panic!("(C-not implementable) should only appear on traits!"), _ => continue, } } }, - syn::Item::Trait(t) if export_status(&t.attrs) == ExportStatus::Export => { - if let syn::Visibility::Public(_) = t.vis { - declared.insert(t.ident.clone(), DeclType::Trait(t)); + syn::Item::Trait(t) => { + match export_status(&t.attrs) { + ExportStatus::Export|ExportStatus::NotImplementable => { + if let syn::Visibility::Public(_) = t.vis { + declared.insert(t.ident.clone(), DeclType::Trait(t)); + } + }, + _ => continue, } }, syn::Item::Mod(m) => {