clang-cl is clang for Windows running in MSVC mode. Chromium uses it for
Windows builds. clang-cl is weird in that it defines __clang__ and
_MSC_VER, but *NOT* __GNUC__. This is vaguely analogous to how normal
clang defines __clang__ (what it is) and __GNUC__ (what it is compatible
with).
However, clang-cl still implements most GCC extensions, being clang.
Notably, the way to control -Wformat-literal is still with
__attribute__((__format__)). For better error-checking and strict
-Wformatl-literal compatibility (see
53c478d639), define
GTEST_ATTRIBUTE_PRINTF_ in clang-cl too.
This makes it easier to use GTest in projects that build with the
-Wmissing-declarations warning. This fixes the warning in headers and
source files, though not GTest's own tests as it is rather noisy there.
On platforms with std::tuple and not std::tr1::tuple, GTEST_HAS_COMBINE
gets turned off when it works fine (due to GTEST_TUPLE_NAMESPACE_).
Elsewhere in the project, several GTEST_HAS_TR1_TUPLE checks
additionally check GTEST_HAS_STD_TUPLE_, so use that formulation.
(The ones that don't are specific to std::tr1::tuple and are followed by
an identical GTEST_HAS_STD_TUPLE_ version underneath it.)
In particular, this fixes testing::Combine on MSVC 2017, which regressed
here:
https://github.com/google/googletest/pull/1348#issuecomment-353879010
ThreadLocal class needs to be have default visibility.
Root cause is gtest uses typeinfo for the ThreadLocal class.
The problem manifests When gtest/gmock are built as a shared library
with libc++. When a class is used in typeinfo, it must have default
visibility.
There is an explanation about typeinfo and visibility here:
https://developer.apple.com/library/content/documentation/DeveloperTools/Conceptual/CppRuntimeEnv/Articles/SymbolVisibility.html
When libc++ is used with gtest in shared library mode, any tests
that are compiled with -fvisibility=hidden and exercise the
macro EXPECT_CALL, it results in an abort like:
[ FATAL ] /usr/include/gtest/internal/gtest-port.h:1394::
Condition typeid(*base) == typeid(Derived) failed.
This is because the typeinfo for ThreadLocal class is not visible.
Therefore, linker failed to match it to the shared library symbol, creating a
new symbol instead.
This fixes https://github.com/google/googletest/issues/1207.
TempDir() function is declared twice, once in `internal/gtest-port.h`
and a second time in `gtest.h`.
Fixes a warning with GCC when -Wredundant-decls is given.
