GCC fix: Make UUID POD

This eliminates all constructors, but nearly all points of use were
using the default constructor to initialize a UUID member variable as in
uuid_(). This syntax will still produce a zeroed-out UUID.

While compiling, for example, minidump_rva_list_writer.cc:

In file included from ../../minidump/minidump_rva_list_writer.h:25:0,
                 from ../../minidump/minidump_rva_list_writer.cc:15:
../../minidump/minidump_extensions.h:412:8: error: ignoring packed attribute because of unpacked non-POD field ‘crashpad::UUID crashpad::MinidumpCrashpadInfo::report_id’ [-Werror]
   UUID report_id;
        ^~~~~~~~~
../../minidump/minidump_extensions.h:424:8: error: ignoring packed attribute because of unpacked non-POD field ‘crashpad::UUID crashpad::MinidumpCrashpadInfo::client_id’ [-Werror]
   UUID client_id;
        ^~~~~~~~~

Tested with:
 - GCC 4.9 from NDK r13 targeting arm with SDK 16
 - GCC 4.9 from NDK r13 targeting arm64 with SDK 21
 - GCC 6.2 targeting x86_64

BUG=crashpad:30

Change-Id: Iec6b1557441b69d75246f2f75c59c4158fb7ca29
Reviewed-on: https://chromium-review.googlesource.com/409641
Reviewed-by: Scott Graham <scottmg@chromium.org>

snapshot/win/process_snapshot_win_test.cc

@@ -31,7 +31,8 @@ namespace test {
 namespace {
 
 void TestImageReaderChild(const base::string16& directory_modification) {
-  UUID done_uuid(UUID::InitializeWithNewTag{});
+  UUID done_uuid;
+  done_uuid.InitializeWithNew();
   ScopedKernelHANDLE done(
       CreateEvent(nullptr, true, false, done_uuid.ToString16().c_str()));
   ASSERT_TRUE(done.get());

util/misc/uuid.cc

@@ -42,23 +42,15 @@ namespace crashpad {
 static_assert(sizeof(UUID) == 16, "UUID must be 16 bytes");
 
 #if CXX_LIBRARY_VERSION >= 2011
-static_assert(std::is_standard_layout<UUID>::value,
-              "UUID must be standard layout");
+static_assert(std::is_pod<UUID>::value, "UUID must be POD");
 #endif
 
-UUID::UUID() : data_1(0), data_2(0), data_3(0), data_4(), data_5() {
-}
-
-UUID::UUID(InitializeWithNewTag) {
-  CHECK(InitializeWithNew());
-}
-
-UUID::UUID(const uint8_t* bytes) {
-  InitializeFromBytes(bytes);
-}
-
 bool UUID::operator==(const UUID& that) const {
-  return memcmp(this, &that, sizeof(UUID)) == 0;
+  return memcmp(this, &that, sizeof(*this)) == 0;
+}
+
+void UUID::InitializeToZero() {
+  memset(this, 0, sizeof(*this));
 }
 
 void UUID::InitializeFromBytes(const uint8_t* bytes) {
@@ -132,7 +124,7 @@ void UUID::InitializeFromSystemUUID(const ::UUID* system_uuid) {
                 "unexpected system uuid size");
   static_assert(offsetof(::UUID, Data1) == offsetof(UUID, data_1),
                 "unexpected system uuid layout");
-  memcpy(this, system_uuid, sizeof(::UUID));
+  memcpy(this, system_uuid, sizeof(*this));
 }
 #endif  // OS_WIN
 

util/misc/uuid.h

@@ -36,27 +36,14 @@ namespace crashpad {
 //!
 //! A %UUID is a unique 128-bit number specified by RFC 4122.
 //!
-//! This is a standard-layout structure.
+//! This is a POD structure.
 struct UUID {
-  //! \brief Initializes the %UUID to zero.
-  UUID();
-
-  //! \brief Tag to pass to constructor to indicate it should initialize with
-  //!     generated data.
-  struct InitializeWithNewTag {};
-
-  //! \brief Initializes the %UUID using a standard system facility to generate
-  //!     the value.
-  //!
-  //! CHECKs on failure with a message logged.
-  explicit UUID(InitializeWithNewTag);
-
-  //! \copydoc InitializeFromBytes()
-  explicit UUID(const uint8_t* bytes);
-
   bool operator==(const UUID& that) const;
   bool operator!=(const UUID& that) const { return !operator==(that); }
 
+  //! \brief Initializes the %UUID to zero.
+  void InitializeToZero();
+
   //! \brief Initializes the %UUID from a sequence of bytes.
   //!
   //! \a bytes is taken as a %UUID laid out in big-endian format in memory. On

util/misc/uuid_test.cc

@@ -31,6 +31,7 @@ namespace {
 
 TEST(UUID, UUID) {
   UUID uuid_zero;
+  uuid_zero.InitializeToZero();
   EXPECT_EQ(0u, uuid_zero.data_1);
   EXPECT_EQ(0u, uuid_zero.data_2);
   EXPECT_EQ(0u, uuid_zero.data_3);
@@ -60,7 +61,8 @@ TEST(UUID, UUID) {
                               0x0d,
                               0x0e,
                               0x0f};
-  UUID uuid(kBytes);
+  UUID uuid;
+  uuid.InitializeFromBytes(kBytes);
   EXPECT_EQ(0x00010203u, uuid.data_1);
   EXPECT_EQ(0x0405u, uuid.data_2);
   EXPECT_EQ(0x0607u, uuid.data_3);
@@ -78,7 +80,8 @@ TEST(UUID, UUID) {
   EXPECT_FALSE(uuid == uuid_zero);
   EXPECT_NE(uuid, uuid_zero);
 
-  UUID uuid_2(kBytes);
+  UUID uuid_2;
+  uuid_2.InitializeFromBytes(kBytes);
   EXPECT_EQ(uuid, uuid_2);
   EXPECT_FALSE(uuid != uuid_2);
 
@@ -155,7 +158,8 @@ TEST(UUID, UUID) {
   EXPECT_EQ(0x45u, uuid.data_5[5]);
   EXPECT_EQ("45454545-4545-4545-4545-454545454545", uuid.ToString());
 
-  UUID initialized_generated(UUID::InitializeWithNewTag{});
+  UUID initialized_generated;
+  initialized_generated.InitializeWithNew();
   EXPECT_NE(initialized_generated, uuid_zero);
 }
 
@@ -182,7 +186,9 @@ TEST(UUID, FromString) {
     {"6d247a34-53d5-40ec-a90d-d8dea9e94cc01", false}
   };
 
-  const std::string empty_uuid = UUID().ToString();
+  UUID uuid_zero;
+  uuid_zero.InitializeToZero();
+  const std::string empty_uuid = uuid_zero.ToString();
 
   for (size_t index = 0; index < arraysize(kCases); ++index) {
     const TestCase& test_case = kCases[index];
@@ -190,6 +196,7 @@ TEST(UUID, FromString) {
         "index %" PRIuS ": %s", index, test_case.uuid_string));
 
     UUID uuid;
+    uuid.InitializeToZero();
     EXPECT_EQ(test_case.success,
               uuid.InitializeFromString(test_case.uuid_string));
     if (test_case.success) {

util/win/process_info_test.cc

@@ -132,7 +132,8 @@ TEST(ProcessInfo, Self) {
 void TestOtherProcess(const base::string16& directory_modification) {
   ProcessInfo process_info;
 
-  UUID done_uuid(UUID::InitializeWithNewTag{});
+  UUID done_uuid;
+  done_uuid.InitializeWithNew();
 
   ScopedKernelHANDLE done(
       CreateEvent(nullptr, true, false, done_uuid.ToString16().c_str()));