From 3a874d936b2fcbb1c77b146d8b1d651e52eb618f Mon Sep 17 00:00:00 2001 From: Pierre-Emmanuel Patry Date: Mon, 23 Oct 2023 15:00:54 +0200 Subject: [PATCH] gccrs: Document proc macro token tree indices Multiple references to procedural macro token trees were left as magic number in the code. This commit introduces some constexpr for those along some explanation for the selected value. gcc/rust/ChangeLog: * backend/rust-compile-base.cc (get_attributes): Add documentation for indices 3 and 4. (get_trait_name): Add documentation for index 1. Signed-off-by: Pierre-Emmanuel Patry --- gcc/rust/backend/rust-compile-base.cc | 27 +++++++++++++++++++++++---- 1 file changed, 23 insertions(+), 4 deletions(-) diff --git a/gcc/rust/backend/rust-compile-base.cc b/gcc/rust/backend/rust-compile-base.cc index fe6d5e3380f..b4a3685ad93 100644 --- a/gcc/rust/backend/rust-compile-base.cc +++ b/gcc/rust/backend/rust-compile-base.cc @@ -165,12 +165,24 @@ get_attributes (const AST::Attribute &attr) // TODO: Should we rely on fixed index ? Should we search for the // attribute tokentree instead ? - if (tt.get_token_trees ().size () > 3) + + // Derive proc macros have the following format: + // #[proc_macro_derive(TraitName, attributes(attr1, attr2, attr3))] + // -~~~~~~~~ - ~~~~~~~~~~--------------------- + // ^0 ^1 ^2 ^3 ^4 + // - "attributes" is stored at position 3 in the token tree + // - attribute are stored in the delimited token tree in position 4 + constexpr size_t attr_kw_pos = 3; + constexpr size_t attribute_list_pos = 4; + + if (tt.get_token_trees ().size () > attr_kw_pos) { - rust_assert (tt.get_token_trees ()[3]->as_string () == "attributes"); + rust_assert (tt.get_token_trees ()[attr_kw_pos]->as_string () + == "attributes"); auto attributes = static_cast ( - tt.get_token_trees ()[4].get ()); + tt.get_token_trees ()[attribute_list_pos].get ()); + auto &token_trees = attributes->get_token_trees (); for (auto i = token_trees.cbegin () + 1; // Skip opening parenthesis @@ -186,11 +198,18 @@ get_attributes (const AST::Attribute &attr) static std::string get_trait_name (const AST::Attribute &attr) { + // Derive proc macros have the following format: + // #[proc_macro_derive(TraitName, attributes(attr1, attr2, attr3))] + // -~~~~~~~~ - ~~~~~~~~~~--------------------- + // ^0 ^1 ^2 ^3 ^4 + // - The trait name is stored at position 1 + constexpr size_t trait_name_pos = 1; + rust_assert (attr.get_attr_input ().get_attr_input_type () == Rust::AST::AttrInput::TOKEN_TREE); const auto &tt = static_cast (attr.get_attr_input ()); - return tt.get_token_trees ()[1]->as_string (); + return tt.get_token_trees ()[trait_name_pos]->as_string (); } void -- 2.11.4.GIT