Update clang_check_attributes to take into account MT_DISABLED (#4479)

nodist/clang_check_attributes

@@ -10,23 +10,37 @@ import argparse
 import os
 import sys
 import shlex
-from typing import Callable, Iterable, Optional, Union
+from typing import Callable, Iterable, Optional, Union, TYPE_CHECKING
 import dataclasses
 from dataclasses import dataclass
 import enum
 from enum import Enum
 import multiprocessing
+import re
 import tempfile
 
 import clang.cindex
 from clang.cindex import (
-    CursorKind,
     Index,
     TranslationUnitSaveError,
     TranslationUnitLoadError,
     CompilationDatabase,
 )
 
+if not TYPE_CHECKING:
+    from clang.cindex import CursorKind
+else:
+    # Workaround for missing support for members defined out-of-class in Pylance:
+    # https://github.com/microsoft/pylance-release/issues/2365#issuecomment-1035803067
+
+    class CursorKindMeta(type):
+
+        def __getattr__(cls, name: str) -> clang.cindex.CursorKind:
+            return getattr(clang.cindex.CursorKind, name)
+
+    class CursorKind(clang.cindex.CursorKind, metaclass=CursorKindMeta):
+        pass
+
 
 def fully_qualified_name(node):
     if node is None:
@@ -66,6 +80,7 @@ class VlAnnotations:
     stable_tree: bool = False
     mt_safe_postinit: bool = False
     mt_unsafe: bool = False
+    mt_disabled: bool = False
     mt_unsafe_one: bool = False
     pure: bool = False
     guarded: bool = False
@@ -87,7 +102,7 @@ class VlAnnotations:
         return self.stable_tree or self.mt_start
 
     def is_mt_unsafe_call(self):
-        return self.mt_unsafe or self.mt_unsafe_one
+        return self.mt_unsafe or self.mt_unsafe_one or self.mt_disabled
 
     def is_mt_safe_call(self):
         return (not self.is_mt_unsafe_call()
@@ -137,6 +152,8 @@ class VlAnnotations:
                     result.mt_unsafe = True
                 elif node.displayname == "MT_UNSAFE_ONE":
                     result.mt_unsafe_one = True
+                elif node.displayname == "MT_DISABLED":
+                    result.mt_disabled = True
                 elif node.displayname == "PURE":
                     result.pure = True
                 elif node.displayname in ["ACQUIRE", "ACQUIRE_SHARED"]:
@@ -209,6 +226,19 @@ class FunctionInfo:
     def copy(self, /, **changes):
         return dataclasses.replace(self, **changes)
 
+    @staticmethod
+    def from_decl_file_line_and_refd_node(file: str, line: int,
+                                          refd: clang.cindex.Cursor,
+                                          annotations: VlAnnotations):
+        file = os.path.abspath(file)
+        refd = refd.canonical
+        assert refd is not None
+        name_parts = fully_qualified_name(refd)
+        usr = refd.get_usr()
+        ftype = FunctionType.from_node(refd)
+
+        return FunctionInfo(name_parts, usr, file, line, annotations, ftype)
+
     @staticmethod
     def from_node(node: clang.cindex.Cursor,
                   refd: Optional[clang.cindex.Cursor] = None,
@@ -234,6 +264,7 @@ class DiagnosticKind(Enum):
     NON_PURE_CALL_IN_PURE_CTX = enum.auto()
     NON_MT_SAFE_CALL_IN_MT_SAFE_CTX = enum.auto()
     NON_STABLE_TREE_CALL_IN_STABLE_TREE_CTX = enum.auto()
+    MISSING_MT_DISABLED_ANNOTATION = enum.auto()
 
     def __lt__(self, other):
         return self.value < other.value
@@ -271,35 +302,142 @@ class CallAnnotationsValidator:
 
         self._index = Index.create()
 
-        self._processed_headers: set[str] = set()
+        # Map key represents translation unit initial defines
+        # (from command line and source's lines before any include)
+        self._processed_headers: dict[str, set[str]] = {}
+        self._external_decls: dict[str, set[tuple[str, int]]] = {}
 
         # Current context
+        self._main_source_file: str = ""
+        self._defines: dict[str, str] = {}
         self._call_location: Optional[FunctionInfo] = None
         self._caller: Optional[FunctionInfo] = None
-        self._level: int = 0
         self._constructor_context: list[clang.cindex.Cursor] = []
+        self._level: int = 0
+
+    def is_mt_disabled_code_unit(self):
+        return "VL_MT_DISABLED_CODE_UNIT" in self._defines
 
     def is_constructor_context(self):
         return len(self._constructor_context) > 0
 
+    # Parses all lines in a form: `#define KEY VALUE` located before any `#include` line.
+    # The parsing is very simple, there is no support for line breaks, etc.
+    @staticmethod
+    def parse_initial_defines(source_file: str) -> dict[str, str]:
+        defs: dict[str, str] = {}
+        with open(source_file, "r", encoding="utf-8") as file:
+            for line in file:
+                line = line.strip()
+                match = re.fullmatch(
+                    r"^#\s*(define\s+(\w+)(?:\s+(.*))?|include\s+.*)$", line)
+                if match:
+                    if match.group(1).startswith("define"):
+                        key = match.group(2)
+                        value = match.groups("1")[2]
+                        defs[key] = value
+                    elif match.group(1).startswith("include"):
+                        break
+        return defs
+
+    @staticmethod
+    def filter_out_unsupported_compiler_args(
+            args: list[str]) -> tuple[list[str], dict[str, str]]:
+        filtered_args = []
+        defines = {}
+        args_iter = iter(args)
+        try:
+            while arg := next(args_iter):
+                # Skip positional arguments (input file name).
+                if not arg.startswith("-") and (arg.endswith(".cpp")
+                                                or arg.endswith(".c")
+                                                or arg.endswith(".h")):
+                    continue
+
+                # Skipped options with separate value argument.
+                if arg in ["-o", "-T", "-MT", "-MQ", "-MF"
+                           "-L"]:
+                    next(args_iter)
+                    continue
+
+                # Skipped options without separate value argument.
+                if arg == "-c" or arg.startswith("-W") or arg.startswith("-L"):
+                    continue
+
+                # Preserved options with separate value argument.
+                if arg in [
+                        "-x"
+                        "-Xclang", "-I", "-isystem", "-iquote", "-include",
+                        "-include-pch"
+                ]:
+                    filtered_args += [arg, next(args_iter)]
+                    continue
+
+                kv_str = None
+                d_or_u = None
+                # Preserve define/undefine with separate value argument.
+                if arg in ["-D", "-U"]:
+                    filtered_args.append(arg)
+                    d_or_u = arg[1]
+                    kv_str = next(args_iter)
+                    filtered_args.append(kv_str)
+                # Preserve define/undefine without separate value argument.
+                elif arg[0:2] in ["-D", "-U"]:
+                    filtered_args.append(arg)
+                    kv_str = arg[2:]
+                    d_or_u = arg[1]
+                # Preserve everything else.
+                else:
+                    filtered_args.append(arg)
+                    continue
+
+                # Keep track of defines for class' internal purposes.
+                key_value = kv_str.split("=", 1)
+                key = key_value[0]
+                val = "1" if len(key_value) == 1 else key_value[1]
+
+                if d_or_u == "D":
+                    defines[key] = val
+                elif d_or_u == "U" and key in defines:
+                    del defines[key]
+
+        except StopIteration:
+            pass
+
+        return (filtered_args, defines)
+
     def compile_and_analyze_file(self, source_file: str,
                                  compiler_args: list[str],
                                  build_dir: Optional[str]):
         filename = os.path.abspath(source_file)
         initial_cwd = "."
 
+        filtered_args, defines = self.filter_out_unsupported_compiler_args(
+            compiler_args)
+        defines.update(self.parse_initial_defines(source_file))
+
         if build_dir:
             initial_cwd = os.getcwd()
             os.chdir(build_dir)
-        translation_unit = self._index.parse(filename, compiler_args)
+        try:
-        has_errors = False
+            translation_unit = self._index.parse(filename, filtered_args)
-        for diag in translation_unit.diagnostics:
+        except TranslationUnitLoadError:
-            if diag.severity > clang.cindex.Diagnostic.Error:
+            translation_unit = None
-                has_errors = True
+        errors = []
-        if translation_unit and not has_errors:
+        if translation_unit:
+            for diag in translation_unit.diagnostics:
+                if diag.severity >= clang.cindex.Diagnostic.Error:
+                    errors.append(str(diag))
+        if translation_unit and len(errors) == 0:
+            self._defines = defines
+            self._main_source_file = filename
             self.process_translation_unit(translation_unit)
+            self._main_source_file = ""
+            self._defines = {}
         else:
             print(f"%Error: parsing failed: {filename}", file=sys.stderr)
+            for error in errors:
+                print(f"        {error}", file=sys.stderr)
         if build_dir:
             os.chdir(initial_cwd)
 
@@ -569,6 +707,18 @@ class CallAnnotationsValidator:
                   f"    from: {node.location.file.name}:{node.location.line}")
         return True
 
+    def process_function_declaration(self, node: clang.cindex.Cursor):
+        # Ignore declarations in main .cpp file
+        if node.location.file.name != self._main_source_file:
+            children = list(node.get_children())
+            annotations = VlAnnotations.from_nodes_list(children)
+            if not annotations.mt_disabled:
+                self._external_decls.setdefault(node.get_usr(), set()).add(
+                    (str(node.location.file.name), int(node.location.line)))
+            return self.iterate_children(children, self.dispatch_node)
+
+        return self.iterate_children(node.get_children(), self.dispatch_node)
+
     # Definition handling
 
     def dispatch_node_inside_definition(self, node: clang.cindex.Cursor):
@@ -599,6 +749,18 @@ class CallAnnotationsValidator:
         assert refd is not None
 
         def_annotations = VlAnnotations.from_nodes_list(node_children)
+        # Implicitly mark definitions in VL_MT_DISABLED_CODE_UNIT .cpp files as
+        # VL_MT_DISABLED. Existence of the annotation on declarations in .h
+        # files is verified below.
+        # Also sets VL_REQUIRES, as this annotation is added together with
+        # explicit VL_MT_DISABLED.
+        if self.is_mt_disabled_code_unit():
+            if node.location.file.name == self._main_source_file:
+                annotations.mt_disabled = True
+                annotations.requires = True
+            if refd.location.file.name == self._main_source_file:
+                def_annotations.mt_disabled = True
+                def_annotations.requires = True
 
         if not (def_annotations.is_empty() or def_annotations == annotations):
             # Use definition's annotations for the diagnostic
@@ -611,12 +773,26 @@ class CallAnnotationsValidator:
                 DiagnosticKind.ANNOTATIONS_DEF_DECL_MISMATCH)
 
         # Use concatenation of definition and declaration annotations
-        # for callees validation.
+        # for calls validation.
         self._caller = FunctionInfo.from_node(node, refd,
                                               def_annotations | annotations)
         prev_call_location = self._call_location
         self._call_location = self._caller
 
+        if self.is_mt_disabled_code_unit():
+            # Report declarations of this functions that don't have MT_DISABLED annotation
+            # and are located in headers.
+            if node.location.file.name == self._main_source_file:
+                usr = node.get_usr()
+                declarations = self._external_decls.get(usr, set())
+                for file, line in declarations:
+                    self.emit_diagnostic(
+                        FunctionInfo.from_decl_file_line_and_refd_node(
+                            file, line, refd, def_annotations),
+                        DiagnosticKind.MISSING_MT_DISABLED_ANNOTATION)
+                if declarations:
+                    del self._external_decls[usr]
+
         self.iterate_children(node_children,
                               self.dispatch_node_inside_definition)
 
@@ -628,34 +804,36 @@ class CallAnnotationsValidator:
     # Nodes not located inside definition
 
     def dispatch_node(self, node: clang.cindex.Cursor):
-        if node.is_definition() and node.kind in [
+        if node.kind in [
                 CursorKind.CXX_METHOD, CursorKind.FUNCTION_DECL,
                 CursorKind.CONSTRUCTOR, CursorKind.CONVERSION_FUNCTION
         ]:
-            return self.process_function_definition(node)
+            if node.is_definition():
-        if node.is_definition() and node.kind in [
+                return self.process_function_definition(node)
-                CursorKind.NAMESPACE, CursorKind.STRUCT_DECL,
+            # else:
-                CursorKind.UNION_DECL, CursorKind.CLASS_DECL
+            return self.process_function_declaration(node)
-        ]:
-            return self.iterate_children(node.get_children(),
-                                         self.dispatch_node)
 
         return self.iterate_children(node.get_children(), self.dispatch_node)
 
     def process_translation_unit(
             self, translation_unit: clang.cindex.TranslationUnit):
         self._level += 1
+        kv_defines = sorted([f"{k}={v}" for k, v in self._defines.items()])
+        concat_defines = '\n'.join(kv_defines)
+        # List of headers already processed in a TU with specified set of defines.
+        tu_processed_headers = self._processed_headers.setdefault(
+            concat_defines, set())
         for child in translation_unit.cursor.get_children():
             if self._is_ignored_top_level(child):
                 continue
-            if self._processed_headers:
+            if tu_processed_headers:
                 filename = os.path.abspath(child.location.file.name)
-                if filename in self._processed_headers:
+                if filename in tu_processed_headers:
                     continue
             self.dispatch_node(child)
         self._level -= 1
 
-        self._processed_headers.update([
+        tu_processed_headers.update([
             os.path.abspath(str(hdr.source))
             for hdr in translation_unit.get_includes()
         ])
@@ -717,34 +895,40 @@ def get_filter_funcs(verilator_root: str):
 
 
 def precompile_header(compile_command: CompileCommand, tmp_dir: str) -> str:
+    initial_cwd = os.getcwd()
+    errors = []
     try:
-        initial_cwd = os.getcwd()
         os.chdir(compile_command.directory)
 
         index = Index.create()
         translation_unit = index.parse(compile_command.filename,
                                        compile_command.args)
         for diag in translation_unit.diagnostics:
-            if diag.severity > clang.cindex.Diagnostic.Error:
+            if diag.severity >= clang.cindex.Diagnostic.Error:
-                pch_file = None
+                errors.append(str(diag))
-                break
+
-        else:
+        if len(errors) == 0:
             pch_file = os.path.join(
                 tmp_dir,
                 f"{compile_command.refid:02}_{os.path.basename(compile_command.filename)}.pch"
             )
             translation_unit.save(pch_file)
 
+            if pch_file:
+                return pch_file
+
+    except (TranslationUnitSaveError, TranslationUnitLoadError,
+            OSError) as exception:
+        print(f"%Warning: {exception}", file=sys.stderr)
+
+    finally:
         os.chdir(initial_cwd)
 
-        if pch_file:
-            return pch_file
-
-    except (TranslationUnitSaveError, TranslationUnitLoadError, OSError):
-        pass
-
     print(
-        f"%Warning: Precompiling failed, skipping: {compile_command.filename}")
+        f"%Warning: Precompilation failed, skipping: {compile_command.filename}",
+        file=sys.stderr)
+    for error in errors:
+        print(f"          {error}", file=sys.stderr)
     return ""
 
 
@@ -887,6 +1071,10 @@ class TopDownSummaryPrinter():
                 name += "is pure but calls non-pure function(s)"
             elif func.reason == DiagnosticKind.NON_STABLE_TREE_CALL_IN_STABLE_TREE_CTX:
                 name += "is stable_tree but calls non-stable_tree or non-mtsafe"
+            elif func.reason == DiagnosticKind.MISSING_MT_DISABLED_ANNOTATION:
+                name += ("defined in a file marked as " +
+                         "VL_MT_DISABLED_CODE_UNIT has declaration(s) " +
+                         "without VL_MT_DISABLED annotation")
             else:
                 name += "for unknown reason (please add description)"
 

test_regress/t/t_a5_attributes_src.pl

@@ -10,20 +10,20 @@ if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); di
 
 scenarios(dist => 1);
 rerunnable(0);
+my $root = "..";
 if ($ENV{VERILATOR_TEST_NO_ATTRIBUTES}) {
     skip("Skipping due to VERILATOR_TEST_NO_ATTRIBUTES");
+} elsif (! -e "$root/src/obj_dbg/compile_commands.json") {
+    skip("compile_commands.json not found. Please install 'bear > 3.0' and rebuild Verilator.");
 } else {
     check();
 }
 sub check {
-    my $root = "..";
     # some of the files are only used in Verilation
     # and are only in "include" folder
     my @srcfiles = grep { !/\/(V3Const|Vlc\w*|\w*_test|\w*_sc|\w*.yy).cpp$/ }
-                   glob("$root/src/*.cpp $root/src/obj_opt/V3Const__gen.cpp");
+                   glob("$root/src/*.cpp $root/src/obj_dbg/V3Const__gen.cpp");
     my $srcfiles_str = join(" ", @srcfiles);
-    my $precompile_args = "-c $root/src/V3Ast.h";
-    my $clang_args = "-I$root/src/ -I$root/include/ -I$root/src/obj_opt/ -fcoroutines-ts";
 
     sub run_clang_check {
         {
@@ -34,7 +34,12 @@ sub check {
         }
         run(logfile => $Self->{run_log_filename},
             tee => 1,
-            cmd => ["python3", "$root/nodist/clang_check_attributes --verilator-root=$root --cxxflags='$clang_args' $precompile_args $srcfiles_str"]);
+            cmd => ["python3",
+                    "$root/nodist/clang_check_attributes",
+                    "--verilator-root=$root",
+                    "--compilation-root=$root/src/obj_dbg",
+                    "--compile-commands-dir=$root/src/obj_dbg",
+                    "$srcfiles_str"]);
 
         file_grep($Self->{run_log_filename}, "Number of functions reported unsafe: 0");
     }

test_regress/t/t_dist_attributes/mt_disabled.cpp

@@ -0,0 +1,44 @@
+// -*- mode: C++; c-file-style: "cc-mode" -*-
+//
+//*************************************************************************
+//
+// Code available from: https://verilator.org
+//
+// Copyright 2022-2023 by Wilson Snyder. This program is free software; you can
+// redistribute it and/or modify it under the terms of either the GNU
+// Lesser General Public License Version 3 or the Perl Artistic License
+// Version 2.0.
+// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+//
+//*************************************************************************
+
+#define VL_MT_DISABLED_CODE_UNIT 1
+
+#include "mt_disabled.h"
+#include "mt_enabled.h"
+
+void unannotatedMtDisabledFunctionBad() {
+}
+
+void UnannotatedMtDisabledClass::unannotatedMtDisabledMethodBad() {
+}
+
+void UnannotatedMtDisabledClass::unannotatedMtDisabledStaticMethodBad() {
+}
+
+// Declarations in .cpp don't have to be annotated with VL_MT_DISABLED.
+void annotatedMtDisabledFunctionOK();
+
+void annotatedMtDisabledFunctionOK() {
+    VerilatedMutex m;
+    // REQUIRES should be ignored and mutex locking not needed.
+    nsf_aa_VL_REQUIRES(m);
+}
+
+void AnnotatedMtDisabledClass::annotatedMtDisabledMethodOK() {
+    annotatedMtDisabledFunctionOK();
+}
+
+void AnnotatedMtDisabledClass::annotatedMtDisabledStaticMethodOK() {
+    annotatedMtDisabledFunctionOK();
+}

test_regress/t/t_dist_attributes/mt_disabled.h

@@ -0,0 +1,50 @@
+// -*- mode: C++; c-file-style: "cc-mode" -*-
+//
+//*************************************************************************
+//
+// Code available from: https://verilator.org
+//
+// Copyright 2022-2023 by Wilson Snyder. This program is free software; you can
+// redistribute it and/or modify it under the terms of either the GNU
+// Lesser General Public License Version 3 or the Perl Artistic License
+// Version 2.0.
+// SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
+//
+//*************************************************************************
+
+#ifndef T_DIST_ATTRIBUTES_MT_DISABLED_H_
+#define T_DIST_ATTRIBUTES_MT_DISABLED_H_
+
+#include "verilatedos.h"
+
+#include "V3ThreadSafety.h"
+
+void unannotatedMtDisabledFunctionBad();
+
+// Duplicate to check that every declaration is reported
+void unannotatedMtDisabledFunctionBad();
+
+class UnannotatedMtDisabledClass final {
+public:
+    void unannotatedMtDisabledMethodBad();
+    static void unannotatedMtDisabledStaticMethodBad();
+
+    int unannotatedInlineMethodOK() const { return 42; }
+    static int unannotatedInlineStaticMethodOK() { return -42; }
+};
+
+void annotatedMtDisabledFunctionOK() VL_MT_DISABLED;
+
+// Duplicate
+void annotatedMtDisabledFunctionOK() VL_MT_DISABLED;
+
+class AnnotatedMtDisabledClass final {
+public:
+    void annotatedMtDisabledMethodOK() VL_MT_DISABLED;
+    static void annotatedMtDisabledStaticMethodOK() VL_MT_DISABLED;
+
+    int annotatedInlineMethodOK() const VL_MT_DISABLED { return 42; }
+    static int annotatedInlineStaticMethodOK() VL_MT_DISABLED { return -42; }
+};
+
+#endif  // T_DIST_ATTRIBUTES_MT_DISABLED_H_

test_regress/t/t_dist_attributes/mt_enabled.cpp

@@ -14,7 +14,7 @@
 
 #include "verilatedos.h"
 
-#include "t_dist_attributes_bad.h"
+#include "mt_enabled.h"
 
 // Non-Static Functions, Annotated declaration, Unannotated definition.
 // (definitions)

test_regress/t/t_dist_attributes/mt_enabled.h

@@ -12,8 +12,8 @@
 //
 //*************************************************************************
 
-#ifndef T_DIST_ATTRIBUTES_BAD_H_
+#ifndef T_DIST_ATTRIBUTES_MT_ENABLED_H_
-#define T_DIST_ATTRIBUTES_BAD_H_
+#define T_DIST_ATTRIBUTES_MT_ENABLED_H_
 
 #include "verilatedos.h"
 
@@ -410,4 +410,4 @@ class TestClassConstructor {
     }
 };
 
-#endif  // T_DIST_ATTRIBUTES_BAD_H_
+#endif  // T_DIST_ATTRIBUTES_MT_ENABLED_H_

test_regress/t/t_dist_attributes_bad.pl

@@ -8,17 +8,65 @@ if (!$::Driver) { use FindBin; exec("$FindBin::Bin/bootstrap.pl", @ARGV, $0); di
 # Version 2.0.
 # SPDX-License-Identifier: LGPL-3.0-only OR Artistic-2.0
 
+use Cwd qw(abs_path);
+use JSON::PP;
+use IO::File;
+
 scenarios(dist => 1);
 if ($ENV{VERILATOR_TEST_NO_ATTRIBUTES}) {
     skip("Skipping due to VERILATOR_TEST_NO_ATTRIBUTES");
 } else {
     check();
 }
+
+sub gen_compile_commands_json {
+    my $json = JSON::PP->new->utf8->pretty;
+
+    my $root_dir = abs_path("..");
+    my $srcs_dir = abs_path("./t/t_dist_attributes");
+    my @common_args = ("clang++",
+                       "-std=c++14",
+                       "-I$root_dir/include",
+                       "-I$root_dir/src",
+                       "-c");
+
+    my $ccjson = [
+        {"directory" => "$srcs_dir",
+         "file" => "$srcs_dir/mt_enabled.cpp",
+         "output" => undef,
+         "arguments" => [@common_args]},
+        {"directory" => "$srcs_dir",
+         "file" => "$srcs_dir/mt_disabled.cpp",
+         "output" => undef,
+         "arguments" => [@common_args]},
+    ];
+
+    my @srcfiles;
+    foreach my $entry (@$ccjson) {
+        # Add "output" key
+        ($entry->{"output"} = $entry->{"file"}) =~ s/\.cpp$/.o/;
+        # Add "-o src.o src.cpp" arguments
+        push @{$entry->{"arguments"}}, ("-o", $entry->{"output"}, $entry->{"file"});
+
+        push @srcfiles, $entry->{"file"};
+    }
+
+    return (
+        \@srcfiles,
+        $json->encode($ccjson)
+    );
+}
+
 sub check {
-    my $root = "..";
+    my $root = abs_path("..");
-    my @srcfiles = glob("$root/test_regress/t/t_dist_attributes_bad.cpp");
+    my $ccjson_file = "$Self->{obj_dir}/compile_commands.json";
-    my $srcfiles_str = join(" ", @srcfiles);
+    my ($srcfiles, $ccjson) = gen_compile_commands_json();
-    my $clang_args = "-I$root/include";
+    my $srcfiles_str = join(" ", @$srcfiles);
+    {
+        my $fh = IO::File->new(">$ccjson_file") or die "%Error: $! $ccjson_file";
+        print $fh $ccjson;
+        $fh->close();
+    }
 
     sub run_clang_check {
         {
@@ -32,7 +80,11 @@ sub check {
             # With `--verilator-root` set to the current directory
             # (i.e. `test_regress`) the script will skip annotation issues in
             # headers from the `../include` directory.
-            cmd => ["python3", "$root/nodist/clang_check_attributes --verilator-root=. --cxxflags='$clang_args' $srcfiles_str"]);
+            cmd => ["python3",
+                    "$root/nodist/clang_check_attributes",
+                    "--verilator-root=.",
+                    "--compile-commands-dir=$Self->{obj_dir}",
+                    "$srcfiles_str"]);
 
         files_identical($Self->{run_log_filename}, $Self->{golden_filename});
     }