[cleanup] Msvc warnings (#9263)

* Fix and reenable signed/unsigned warning C4018

* Only disable unary minus warning C4146 in tests

BUILD

@@ -28,9 +28,7 @@ ZLIB_DEPS = ["@zlib//:zlib"]
 ################################################################################
 
 MSVC_COPTS = [
-    "/wd4018",  # -Wno-sign-compare
     "/wd4065",  # switch statement contains 'default' but no 'case' labels
-    "/wd4146",  # unary minus operator applied to unsigned type, result still unsigned
     "/wd4244",  # 'conversion' conversion from 'type1' to 'type2', possible loss of data
     "/wd4251",  # 'identifier' : class 'type' needs to have dll-interface to be used by clients of class 'type2'
     "/wd4267",  # 'var' : conversion from 'size_t' to 'type', possible loss of data

cmake/CMakeLists.txt

@@ -215,9 +215,7 @@ if (MSVC)
   add_definitions(/utf-8)
   # MSVC warning suppressions
   add_definitions(
-    /wd4018 # 'expression' : signed/unsigned mismatch
     /wd4065 # switch statement contains 'default' but no 'case' labels
-    /wd4146 # unary minus operator applied to unsigned type, result still unsigned
     /wd4244 # 'conversion' conversion from 'type1' to 'type2', possible loss of data
     /wd4251 # 'identifier' : class 'type' needs to have dll-interface to be used by clients of class 'type2'
     /wd4267 # 'var' : conversion from 'size_t' to 'type', possible loss of data

cmake/README.md

@@ -320,8 +320,6 @@ The following warnings have been disabled while building the protobuf libraries
 and compiler.  You may have to disable some of them in your own project as
 well, or live with them.
 
-* C4018 - 'expression' : signed/unsigned mismatch
-* C4146 - unary minus operator applied to unsigned type, result still unsigned
 * C4244 - Conversion from 'type1' to 'type2', possible loss of data.
 * C4251 - 'identifier' : class 'type' needs to have dll-interface to be used by
   clients of class 'type2'

cmake/tests.cmake

@@ -222,6 +222,11 @@ if(MINGW)
 endif()
 
 add_executable(tests ${tests_files} ${common_test_files} ${tests_proto_files} ${lite_test_proto_files})
+if (MSVC)
+  target_compile_options(tests PRIVATE
+    /wd4146 # unary minus operator applied to unsigned type, result still unsigned
+  )
+endif()
 target_link_libraries(tests libprotoc libprotobuf gmock_main)
 
 set(test_plugin_files

src/google/protobuf/descriptor.cc

@@ -1007,7 +1007,7 @@ class TableArena {
     }
 
     for (int i = kSmallSizes.size(); --i >= 0;) {
-      if (to_relocate->space_left() >= 1 + kSmallSizes[i]) {
+      if (to_relocate->space_left() >= 1U + kSmallSizes[i]) {
         to_relocate->PrependTo(small_size_blocks_[i]);
         return;
       }

src/google/protobuf/io/io_win32_unittest.cc

@@ -164,8 +164,8 @@ void IoWin32Test::SetUp() {
   test_tmpdir.clear();
   wtest_tmpdir.clear();
   DWORD size = ::GetCurrentDirectoryW(MAX_PATH, working_directory);
-  EXPECT_GT(size, 0);
-  EXPECT_LT(size, MAX_PATH);
+  EXPECT_GT(size, 0U);
+  EXPECT_LT(size, static_cast<DWORD>(MAX_PATH));
 
   string tmp;
   bool ok = false;
@@ -581,7 +581,7 @@ TEST_F(IoWin32Test, ExpandWildcardsFailsIfNoFileMatchesTest) {
 TEST_F(IoWin32Test, AsWindowsPathTest) {
   DWORD size = GetCurrentDirectoryW(0, nullptr);
   std::unique_ptr<wchar_t[]> cwd_str(new wchar_t[size]);
-  EXPECT_GT(GetCurrentDirectoryW(size, cwd_str.get()), 0);
+  EXPECT_GT(GetCurrentDirectoryW(size, cwd_str.get()), 0U);
   wstring cwd = wstring(L"\\\\?\\") + cwd_str.get();
 
   ASSERT_EQ(testonly_utf8_to_winpath("relative_mkdirtest"),

src/google/protobuf/stubs/int128.cc

@@ -173,12 +173,13 @@ std::ostream& operator<<(std::ostream& o, const uint128& b) {
 
   // Add the requisite padding.
   std::streamsize width = o.width(0);
-  if (width > rep.size()) {
+  auto repSize = static_cast<std::streamsize>(rep.size());
+  if (width > repSize) {
     if ((flags & std::ios::adjustfield) == std::ios::left) {
-      rep.append(width - rep.size(), o.fill());
+      rep.append(width - repSize, o.fill());
     } else {
       rep.insert(static_cast<std::string::size_type>(0),
-                 width - rep.size(), o.fill());
+                 width - repSize, o.fill());
     }
   }