rs_bindings_from_cc/ast_visitor.cc

// Part of the Crubit project, under the Apache License v2.0 with LLVM
// Exceptions. See /LICENSE for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

#include "rs_bindings_from_cc/ast_visitor.h"

#include <memory>
#include <string>
#include <utility>
#include <vector>

#include "base/logging.h"
#include "rs_bindings_from_cc/ir.h"
#include "third_party/absl/container/flat_hash_set.h"
#include "third_party/absl/strings/cord.h"
#include "third_party/llvm/llvm-project/clang/include/clang/AST/ASTContext.h"
#include "third_party/llvm/llvm-project/clang/include/clang/AST/Decl.h"
#include "third_party/llvm/llvm-project/clang/include/clang/AST/Mangle.h"
#include "third_party/llvm/llvm-project/clang/include/clang/AST/Type.h"

namespace rs_bindings_from_cc {

bool AstVisitor::TraverseDecl(clang::Decl* decl) {
  if (seen_decls_.insert(decl->getCanonicalDecl()).second) {
    return Base::TraverseDecl(decl);
  }
  return false;
}

bool AstVisitor::TraverseTranslationUnitDecl(
    clang::TranslationUnitDecl* translation_unit_decl) {
  mangler_.reset(translation_unit_decl->getASTContext().createMangleContext());

  // TODO(hlopko): Make the generated C++ code include-what-you-use clean.
  // Currently we pass public headers of the library to the src_code_gen.
  // Through those Clang has access to all declarations needed by the public API
  // of the library. However the code violates IWYU - it will not directly
  // include all the headers declaring names used in the generated source. This
  // could be fixed by passing not only public headers of the library to the
  // tool, but also all public headers of the direct dependencies of the
  // library. This way if the library was IWYU clean, the generated code will be
  // too.
  for (const std::string& header : public_headers_) {
    ir_.UsedHeaders().emplace_back(HeaderName(absl::Cord(header)));
  }

  return Base::TraverseTranslationUnitDecl(translation_unit_decl);
}

bool AstVisitor::VisitFunctionDecl(clang::FunctionDecl* function_decl) {
  // TODO(hlopko): Skip decls from other headers
  // TODO(hlopko): Generate thunks + C++ impls for inline functions
  // TODO(hlopko): Handle lowercased snakecased conflicts
  // TODO(hlopko): Convert primitive types (bool -> bool, int -> i64 (?) and
  // so on)
  // TODO(hlopko): Import return type properly
  // TODO(hlopko): Import parameter types properly
  // TODO(hlopko): Import clang doc comment
  // TODO(hlopko): Handle member functions
  // TODO(hlopko): Handle static member functions
  // TODO(hlopko): Handle constructors/operators/special members
  // TODO(hlopko): Handle destructors
  // TODO(hlopko): Do not import deleted members
  // TODO(hlopko): Handle function templates
  // TODO(hlopko): Do not import private/protected members
  // TODO(hlopko): Handle (?) variadic functions
  // TODO(hlopko): Fail when exceptions enabled?
  std::vector<FuncParam> params;
  for (const clang::ParmVarDecl* param : function_decl->parameters()) {
    params.emplace_back(ConvertType(param->getType()),
                        GetTranslatedName(param));
  }

  ir_.Functions().emplace_back(
      GetTranslatedName(function_decl), GetMangledName(function_decl),
      ConvertType(function_decl->getReturnType()), params);
  return true;
}

Type AstVisitor::ConvertType(clang::QualType qual_type) const {
  // TODO(hlopko): Handle all builtin types
  // TODO(hlopko): Handle user-defined types
  // TODO(hlopko): Handle user-defined types defined elsewhere (with fully
  // qualified paths)
  if (const clang::BuiltinType* builtin_type =
          qual_type->getAs<clang::BuiltinType>()) {
    if (builtin_type->isIntegerType()) {
      // TODO(hlopko): look at the actual width of the type.
      return Type(absl::Cord("i32"));
    }
    if (builtin_type->isVoidType()) {
      return Type::Void();
    }
  }
  LOG(FATAL) << "Unsupported type " << qual_type.getAsString() << "\n";
}

absl::Cord AstVisitor::GetMangledName(
    const clang::NamedDecl* named_decl) const {
  std::string name;
  llvm::raw_string_ostream stream(name);
  mangler_->mangleName(named_decl, stream);
  stream.flush();
  return absl::Cord(std::move(name));
}

Identifier AstVisitor::GetTranslatedName(
    const clang::NamedDecl* named_decl) const {
  // TODO(hlopko): handle the case where the name is not a simple identifier.
  return Identifier(absl::Cord(named_decl->getName()));
}

}  // namespace rs_bindings_from_cc