Fields in system headers (and generated code) are not really affected.

Fields in system headers (and generated) code were not rewritten even
before this CL, because |apply_edits.py| ignores edits that apply to
files that |git| doesn't know anything about.  But, before this CL, such
fields would be considered "affected" and therefore Chromium code might
see |.get()| appended when using such fields in |printf|,
|reinterpret_cast|, etc.  Such inconsistency would lead to build errors
after the rewrite.

After this CL, fields in system headers (and generated code) are
explicitly excluded (early on, in the |field_decl_matcher|).

Bug: 1069567
Change-Id: Icc9735b94558828c002572b38dcef12a812de35c
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2204305
Commit-Queue: Łukasz Anforowicz <lukasza@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Cr-Commit-Position: refs/heads/master@{#775250}

tools/clang/rewrite_raw_ptr_fields/RewriteRawPtrFields.cpp

@@ -183,6 +183,13 @@ AST_MATCHER(clang::FieldDecl, isInThirdPartyLocation) {
   return file_path.contains("third_party");
 }
 
+AST_MATCHER(clang::FieldDecl, isInGeneratedLocation) {
+  llvm::StringRef file_path =
+      GetFilePath(Finder->getASTContext().getSourceManager(), Node);
+
+  return file_path.startswith("gen/") || file_path.contains("/gen/");
+}
+
 class FieldDeclFilterFile {
  public:
   explicit FieldDeclFilterFile(const std::string& filepath) {
@@ -470,12 +477,13 @@ int main(int argc, const char* argv[]) {
   //   the source code)
   FieldDeclFilterFile fields_to_exclude(exclude_fields_param);
   auto field_decl_matcher =
-      fieldDecl(allOf(hasType(supported_pointer_types_matcher),
-                      hasUniqueTypeLoc(),
-                      unless(anyOf(isInThirdPartyLocation(),
-                                   isInMacroLocation(), isInExternCContext(),
-                                   isListedInFilterFile(fields_to_exclude),
-                                   implicit_field_decl_matcher))))
+      fieldDecl(
+          allOf(hasType(supported_pointer_types_matcher), hasUniqueTypeLoc(),
+                unless(anyOf(isInThirdPartyLocation(), isInGeneratedLocation(),
+                             isExpansionInSystemHeader(), isInMacroLocation(),
+                             isInExternCContext(),
+                             isListedInFilterFile(fields_to_exclude),
+                             implicit_field_decl_matcher))))
           .bind("fieldDecl");
   FieldDeclRewriter field_decl_rewriter(&replacements_printer);
   match_finder.addMatcher(field_decl_matcher, &field_decl_rewriter);

tools/clang/rewrite_raw_ptr_fields/tests/affected-expr-expected.cc

@@ -5,6 +5,7 @@
 #include <stdint.h>  // for uintptr_t
 
 #include "base/memory/checked_ptr.h"
+#include "gen/generated_header.h"
 
 class SomeClass {};
 class DerivedClass : public SomeClass {};
@@ -168,3 +169,17 @@ void foo(int x) {
 }
 
 }  // namespace ternary_operator_tests
+
+namespace generated_code_tests {
+
+void MyPrintf(const char* fmt, ...) {}
+
+void foo() {
+  GeneratedStruct s;
+
+  // No rewrite expected below (i.e. no |.get()| appended), because the field
+  // dereferenced below comes from (simulated) generated code.
+  MyPrintf("%p", s.ptr_field);
+}
+
+}  // namespace generated_code_tests

tools/clang/rewrite_raw_ptr_fields/tests/affected-expr-in-system-header-expected.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <stdint.h>
+
+// WARNING: This test uses a platform-specific system header.  This means that
+// the test might (expectedly) fail on platforms that don't provide such header.
+#include <dlfcn.h>
+
+void foo(const Dl_info& dl_info) {
+  // Fields in non-Chromium locations are not affected (e.g. |apply_edits.py|
+  // filters out edit directives that apply to files that |git| doesn't know
+  // about).  For example, |Dl_info::dli_fbase| won't be rewritten and therefore
+  // shouldn't be treated as "affected" in the expression below.
+  //
+  // No rewrite expected below - the expression below shouldn't turn into
+  // |dl_info.dli_fbase.get()|.
+  uintptr_t v = reinterpret_cast<uintptr_t>(dl_info.dli_fbase);
+}

tools/clang/rewrite_raw_ptr_fields/tests/affected-expr-in-system-header-original.cc

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include <stdint.h>
+
+// WARNING: This test uses a platform-specific system header.  This means that
+// the test might (expectedly) fail on platforms that don't provide such header.
+#include <dlfcn.h>
+
+void foo(const Dl_info& dl_info) {
+  // Fields in non-Chromium locations are not affected (e.g. |apply_edits.py|
+  // filters out edit directives that apply to files that |git| doesn't know
+  // about).  For example, |Dl_info::dli_fbase| won't be rewritten and therefore
+  // shouldn't be treated as "affected" in the expression below.
+  //
+  // No rewrite expected below - the expression below shouldn't turn into
+  // |dl_info.dli_fbase.get()|.
+  uintptr_t v = reinterpret_cast<uintptr_t>(dl_info.dli_fbase);
+}

tools/clang/rewrite_raw_ptr_fields/tests/affected-expr-original.cc

@@ -4,6 +4,8 @@
 
 #include <stdint.h>  // for uintptr_t
 
+#include "gen/generated_header.h"
+
 class SomeClass {};
 class DerivedClass : public SomeClass {};
 
@@ -166,3 +168,17 @@ void foo(int x) {
 }
 
 }  // namespace ternary_operator_tests
+
+namespace generated_code_tests {
+
+void MyPrintf(const char* fmt, ...) {}
+
+void foo() {
+  GeneratedStruct s;
+
+  // No rewrite expected below (i.e. no |.get()| appended), because the field
+  // dereferenced below comes from (simulated) generated code.
+  MyPrintf("%p", s.ptr_field);
+}
+
+}  // namespace generated_code_tests

tools/clang/rewrite_raw_ptr_fields/tests/gen/generated_header.h

+// Copyright 2020 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TOOLS_CLANG_REWRITE_RAW_PTR_FIELDS_TESTS_GEN_GENERATED_HEADER_H_
+#define TOOLS_CLANG_REWRITE_RAW_PTR_FIELDS_TESTS_GEN_GENERATED_HEADER_H_
+
+class SomeClass;
+
+// This file simulates a header that was generated during build.  This is
+// simulated by virtue of being located inside a directory named "gen".
+struct GeneratedStruct {
+  // No rewrite expected inside generated code.
+  int* ptr_field;
+  SomeClass* ptr_field2;
+};
+
+#endif  // TOOLS_CLANG_REWRITE_RAW_PTR_FIELDS_TESTS_GEN_GENERATED_HEADER_H_