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LibJSGCVerifier: Detect missing JS_DECLARE_ALLOCATOR() calls

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C++ classes that inherit from JS::Cell and are leaf classes should have
their own type-specific allocator. We also do this for non-leaf classes
that are constructable from JS.

To do this, JSON messages are passed to communicate information about
each class the Clang tool comes across. This is the only message we have
to worry about for now, but in the future if we want to transmit
different kinds of information, we can make this message format more
generic.
This commit is contained in:
Matthew Olsson 2024-04-06 09:44:32 -07:00 • committed by Andreas Kling
parent dfce95ab0f
commit 312bc94ac9
2 changed files with 44 additions and 0 deletions
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30
Meta/Lagom/Tools/LibJSGCVerifier/src/CellsHandler.cpp
View file

@ -14,6 +14,7 @@
#include <clang/Frontend/CompilerInstance.h>
#include <filesystem>
#include <llvm/Support/Casting.h>
#include <llvm/Support/JSON.h>
#include <llvm/Support/raw_ostream.h>
#include <unordered_set>
#include <vector>
@ -230,6 +231,33 @@ FieldValidationResult validate_field(clang::FieldDecl const* field_decl)
return result;
}
void emit_record_json_data(clang::CXXRecordDecl const& record)
{
llvm::json::Object obj;
obj.insert({ "name", record.getQualifiedNameAsString() });
std::vector<std::string> bases;
record.forallBases([&](clang::CXXRecordDecl const* base) {
bases.push_back(base->getQualifiedNameAsString());
return true;
});
obj.insert({ "parents", bases });
bool has_cell_allocator = false;
bool has_js_constructor = false;
for (auto const& decl : record.decls()) {
if (auto* var_decl = llvm::dyn_cast<clang::VarDecl>(decl); var_decl && var_decl->getQualifiedNameAsString().ends_with("::cell_allocator")) {
has_cell_allocator = true;
} else if (auto* fn_decl = llvm::dyn_cast<clang::CXXMethodDecl>(decl); fn_decl && fn_decl->getQualifiedNameAsString().ends_with("::construct_impl")) {
has_js_constructor = true;
}
}
obj.insert({ "has_cell_allocator", has_cell_allocator });
obj.insert({ "has_js_constructor", has_js_constructor });
llvm::outs() << std::move(obj) << "\n";
}
void CollectCellsHandler::run(clang::ast_matchers::MatchFinder::MatchResult const& result)
{
check_cells(result);
@ -278,6 +306,8 @@ void CollectCellsHandler::check_cells(clang::ast_matchers::MatchFinder::MatchRes
if (!record_inherits_from_cell(*record))
return;
emit_record_json_data(*record);
clang::DeclarationName const name = &result.Context->Idents.get("visit_edges");
auto const* visit_edges_method = record->lookup(name).find_first<clang::CXXMethodDecl>();
if (!visit_edges_method && !fields_that_need_visiting.empty()) {

14
Meta/Lagom/Tools/LibJSGCVerifier/src/main.py
View file

@ -92,3 +92,17 @@ with multiprocessing.Pool(processes=multiprocessing.cpu_count() - 2, initializer
except KeyboardInterrupt:
pool.terminate()
pool.join()
# Process output data
clang_results = {r['name']: r for r in clang_results}
leaf_objects = set(clang_results.keys())
for result in clang_results.values():
leaf_objects.difference_update(result['parents'])
for key, value in clang_results.items():
if key == 'JS::HeapBlock::FreelistEntry' or key == 'JS::HeapFunction':
# These are Heap-related classes and don't need their own allocator
continue
if not value['has_cell_allocator'] and (key in leaf_objects or value['has_js_constructor']):
print(f'Class {key} is missing a JS_DECLARE_ALLOCATOR() declaration in its header file')