Optimize Google Test process startup

Google Test performs hidden test registration during process
startup. For test binaries that contain a large number of tests, this
registration can be costly. In this CL, we reduce the overhead of
registration via several tactics:

- Treat CodeLocation and FilePath as value types, using std::move to
  pass them around.
- Reduce string copies in various places by either passing std::string
  values via std::move, or passing const-refs to std::string instances.
- Use std::to_string to stringify an int in DefaultParamName rather than
  a std::stringstream.
- Pull some std::string instances out of nested loops in
  ParameterizedTestSuiteInfo::RegisterTests so as to reuse some
  allocations, and replace stringstream with ordinary string appends.
- Use std::unordered_map in UnitTestImpl::GetTestSuite and
  ParameterizedTestSuiteRegistry::GetTestSuitePatternHolder to spend a
  little memory to turn O(N) lookups into constant time lookpus.
- Use range-based for loops in various places.
- Use emplace-ish methods to add to containers where appropriate.

All together, these changes reduce the overall runtime of a series of 50
death tests in a single Chromium test executable by ~38% due to the
fact that the registration costs are paid in every death test's child
process.

PiperOrigin-RevId: 612763676
Change-Id: I1f46e012ccb9004c009e1027e4f7c38780ffb9e2

googletest/include/gtest/gtest.h

@@ -607,15 +607,15 @@ class GTEST_API_ TestInfo {
   friend class internal::UnitTestImpl;
   friend class internal::StreamingListenerTest;
   friend TestInfo* internal::MakeAndRegisterTestInfo(
-      const char* test_suite_name, const char* name, const char* type_param,
+      std::string test_suite_name, const char* name, const char* type_param,
       const char* value_param, internal::CodeLocation code_location,
       internal::TypeId fixture_class_id, internal::SetUpTestSuiteFunc set_up_tc,
       internal::TearDownTestSuiteFunc tear_down_tc,
       internal::TestFactoryBase* factory);
 
   // Constructs a TestInfo object. The newly constructed instance assumes
   // ownership of the factory object.
-  TestInfo(const std::string& test_suite_name, const std::string& name,
+  TestInfo(std::string test_suite_name, std::string name,
            const char* a_type_param,   // NULL if not a type-parameterized test
            const char* a_value_param,  // NULL if not a value-parameterized test
            internal::CodeLocation a_code_location,
@@ -683,7 +683,7 @@ class GTEST_API_ TestSuite {
   //                 this is not a type-parameterized test.
   //   set_up_tc:    pointer to the function that sets up the test suite
   //   tear_down_tc: pointer to the function that tears down the test suite
-  TestSuite(const char* name, const char* a_type_param,
+  TestSuite(const std::string& name, const char* a_type_param,
             internal::SetUpTestSuiteFunc set_up_tc,
             internal::TearDownTestSuiteFunc tear_down_tc);
 

googletest/include/gtest/internal/gtest-filepath.h

@@ -43,6 +43,7 @@
 #define GOOGLETEST_INCLUDE_GTEST_INTERNAL_GTEST_FILEPATH_H_
 
 #include <string>
+#include <utility>
 
 #include "gtest/internal/gtest-port.h"
 #include "gtest/internal/gtest-string.h"
@@ -70,15 +71,20 @@ class GTEST_API_ FilePath {
  public:
   FilePath() : pathname_("") {}
   FilePath(const FilePath& rhs) : pathname_(rhs.pathname_) {}
+  FilePath(FilePath&& rhs) : pathname_(std::move(rhs.pathname_)) {}
 
-  explicit FilePath(const std::string& pathname) : pathname_(pathname) {
+  explicit FilePath(std::string pathname) : pathname_(std::move(pathname)) {
     Normalize();
   }
 
   FilePath& operator=(const FilePath& rhs) {
     Set(rhs);
     return *this;
   }
+  FilePath& operator=(FilePath&& rhs) {
+    pathname_ = std::move(rhs.pathname_);
+    return *this;
+  }
 
   void Set(const FilePath& rhs) { pathname_ = rhs.pathname_; }
 

googletest/include/gtest/internal/gtest-internal.h

@@ -474,8 +474,8 @@ using SetUpTestSuiteFunc = void (*)();
 using TearDownTestSuiteFunc = void (*)();
 
 struct CodeLocation {
-  CodeLocation(const std::string& a_file, int a_line)
-      : file(a_file), line(a_line) {}
+  CodeLocation(std::string a_file, int a_line)
+      : file(std::move(a_file)), line(a_line) {}
 
   std::string file;
   int line;
@@ -564,7 +564,7 @@ struct SuiteApiResolver : T {
 //                     The newly created TestInfo instance will assume
 //                     ownership of the factory object.
 GTEST_API_ TestInfo* MakeAndRegisterTestInfo(
-    const char* test_suite_name, const char* name, const char* type_param,
+    std::string test_suite_name, const char* name, const char* type_param,
     const char* value_param, CodeLocation code_location,
     TypeId fixture_class_id, SetUpTestSuiteFunc set_up_tc,
     TearDownTestSuiteFunc tear_down_tc, TestFactoryBase* factory);
@@ -595,8 +595,7 @@ class GTEST_API_ TypedTestSuitePState {
       fflush(stderr);
       posix::Abort();
     }
-    registered_tests_.insert(
-        ::std::make_pair(test_name, CodeLocation(file, line)));
+    registered_tests_.emplace(test_name, CodeLocation(file, line));
     return true;
   }
 
@@ -700,7 +699,7 @@ class TypeParameterizedTest {
   // specified in INSTANTIATE_TYPED_TEST_SUITE_P(Prefix, TestSuite,
   // Types).  Valid values for 'index' are [0, N - 1] where N is the
   // length of Types.
-  static bool Register(const char* prefix, const CodeLocation& code_location,
+  static bool Register(const char* prefix, CodeLocation code_location,
                        const char* case_name, const char* test_names, int index,
                        const std::vector<std::string>& type_names =
                            GenerateNames<DefaultNameGenerator, Types>()) {
@@ -712,8 +711,7 @@ class TypeParameterizedTest {
     // list.
     MakeAndRegisterTestInfo(
         (std::string(prefix) + (prefix[0] == '\0' ? "" : "/") + case_name +
-         "/" + type_names[static_cast<size_t>(index)])
-            .c_str(),
+         "/" + type_names[static_cast<size_t>(index)]),
         StripTrailingSpaces(GetPrefixUntilComma(test_names)).c_str(),
         GetTypeName<Type>().c_str(),
         nullptr,  // No value parameter.
@@ -725,21 +723,17 @@ class TypeParameterizedTest {
         new TestFactoryImpl<TestClass>);
 
     // Next, recurses (at compile time) with the tail of the type list.
-    return TypeParameterizedTest<Fixture, TestSel,
-                                 typename Types::Tail>::Register(prefix,
-                                                                 code_location,
-                                                                 case_name,
-                                                                 test_names,
-                                                                 index + 1,
-                                                                 type_names);
+    return TypeParameterizedTest<Fixture, TestSel, typename Types::Tail>::
+        Register(prefix, std::move(code_location), case_name, test_names,
+                 index + 1, type_names);
   }
 };
 
 // The base case for the compile time recursion.
 template <GTEST_TEMPLATE_ Fixture, class TestSel>
 class TypeParameterizedTest<Fixture, TestSel, internal::None> {
  public:
-  static bool Register(const char* /*prefix*/, const CodeLocation&,
+  static bool Register(const char* /*prefix*/, CodeLocation,
                        const char* /*case_name*/, const char* /*test_names*/,
                        int /*index*/,
                        const std::vector<std::string>& =
@@ -786,7 +780,8 @@ class TypeParameterizedTestSuite {
 
     // Next, recurses (at compile time) with the tail of the test list.
     return TypeParameterizedTestSuite<Fixture, typename Tests::Tail,
-                                      Types>::Register(prefix, code_location,
+                                      Types>::Register(prefix,
+                                                       std::move(code_location),
                                                        state, case_name,
                                                        SkipComma(test_names),
                                                        type_names);