Remove C++14 implementation of C++17 STL code in template_util.h.
This is a subset of the work done in https://crbug.com/1320019 for
Chromium's copy of base/template_util.h:
- Switch from pdfium::base::void_t to std::void_t
- Remove workarounds for very old compilers
- Remove pdfium::base::in_place_t and pdfium::base::disjunction
Bug: pdfium:1766
Change-Id: I1a6aeebe067d12eaa37711b9b295b566d78be619
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/93374
Commit-Queue: Lei Zhang <thestig@chromium.org>
Reviewed-by: Tom Sepez <tsepez@chromium.org>
diff --git a/third_party/base/containers/contains.h b/third_party/base/containers/contains.h
index 73218d4..fd2ca35 100644
--- a/third_party/base/containers/contains.h
+++ b/third_party/base/containers/contains.h
@@ -23,29 +23,31 @@
struct HasFindWithNpos<
Container,
Element,
- void_t<decltype(std::declval<const Container&>().find(
- std::declval<const Element&>()) != Container::npos)>>
- : std::true_type {};
+ std::void_t<decltype(std::declval<const Container&>().find(
+ std::declval<const Element&>()) !=
+ Container::npos)>> : std::true_type {};
template <typename Container, typename Element, typename = void>
struct HasFindWithEnd : std::false_type {};
template <typename Container, typename Element>
-struct HasFindWithEnd<Container,
- Element,
- void_t<decltype(std::declval<const Container&>().find(
- std::declval<const Element&>()) !=
- std::declval<const Container&>().end())>>
+struct HasFindWithEnd<
+ Container,
+ Element,
+ std::void_t<decltype(std::declval<const Container&>().find(
+ std::declval<const Element&>()) !=
+ std::declval<const Container&>().end())>>
: std::true_type {};
template <typename Container, typename Element, typename = void>
struct HasContains : std::false_type {};
template <typename Container, typename Element>
-struct HasContains<Container,
- Element,
- void_t<decltype(std::declval<const Container&>().contains(
- std::declval<const Element&>()))>> : std::true_type {};
+struct HasContains<
+ Container,
+ Element,
+ std::void_t<decltype(std::declval<const Container&>().contains(
+ std::declval<const Element&>()))>> : std::true_type {};
} // namespace internal
diff --git a/third_party/base/template_util.h b/third_party/base/template_util.h
index 2e26a8b..895d8dc 100644
--- a/third_party/base/template_util.h
+++ b/third_party/base/template_util.h
@@ -14,28 +14,6 @@
#include "build/build_config.h"
-// Some versions of libstdc++ have partial support for type_traits, but misses
-// a smaller subset while removing some of the older non-standard stuff. Assume
-// that all versions below 5.0 fall in this category, along with one 5.0
-// experimental release. Test for this by consulting compiler major version,
-// the only reliable option available, so theoretically this could fail should
-// you attempt to mix an earlier version of libstdc++ with >= GCC5. But
-// that's unlikely to work out, especially as GCC5 changed ABI.
-#define CR_GLIBCXX_5_0_0 20150123
-#if (defined(__GNUC__) && __GNUC__ < 5) || \
- (defined(__GLIBCXX__) && __GLIBCXX__ == CR_GLIBCXX_5_0_0)
-#define CR_USE_FALLBACKS_FOR_OLD_EXPERIMENTAL_GLIBCXX
-#endif
-
-// This hacks around using gcc with libc++ which has some incompatibilies.
-// - is_trivially_* doesn't work: https://llvm.org/bugs/show_bug.cgi?id=27538
-// TODO(danakj): Remove this when android builders are all using a newer version
-// of gcc, or the android ndk is updated to a newer libc++ that works with older
-// gcc versions.
-#if !defined(__clang__) && defined(_LIBCPP_VERSION)
-#define CR_USE_FALLBACKS_FOR_GCC_WITH_LIBCXX
-#endif
-
namespace pdfium {
template <class T> struct is_non_const_reference : std::false_type {};
@@ -44,25 +22,6 @@
namespace internal {
-// Implementation detail of pdfium::void_t below.
-template <typename...>
-struct make_void {
- using type = void;
-};
-
-} // namespace internal
-
-// pdfium::void_t is an implementation of std::void_t from C++17.
-//
-// We use |pdfium::internal::make_void| as a helper struct to avoid a C++14
-// defect:
-// http://en.cppreference.com/w/cpp/types/void_t
-// http://open-std.org/JTC1/SC22/WG21/docs/cwg_defects.html#1558
-template <typename... Ts>
-using void_t = typename ::pdfium::internal::make_void<Ts...>::type;
-
-namespace internal {
-
// Uses expression SFINAE to detect whether using operator<< would work.
template <typename T, typename = void>
struct SupportsOstreamOperator : std::false_type {};
@@ -79,100 +38,13 @@
struct is_iterator : std::false_type {};
template <typename T>
-struct is_iterator<T,
- void_t<typename std::iterator_traits<T>::iterator_category>>
+struct is_iterator<
+ T,
+ std::void_t<typename std::iterator_traits<T>::iterator_category>>
: std::true_type {};
} // namespace internal
-// is_trivially_copyable is especially hard to get right.
-// - Older versions of libstdc++ will fail to have it like they do for other
-// type traits. This has become a subset of the second point, but used to be
-// handled independently.
-// - An experimental release of gcc includes most of type_traits but misses
-// is_trivially_copyable, so we still have to avoid using libstdc++ in this
-// case, which is covered by CR_USE_FALLBACKS_FOR_OLD_EXPERIMENTAL_GLIBCXX.
-// - When compiling libc++ from before r239653, with a gcc compiler, the
-// std::is_trivially_copyable can fail. So we need to work around that by not
-// using the one in libc++ in this case. This is covered by the
-// CR_USE_FALLBACKS_FOR_GCC_WITH_LIBCXX define, and is discussed in
-// https://llvm.org/bugs/show_bug.cgi?id=27538#c1 where they point out that
-// in libc++'s commit r239653 this is fixed by libc++ checking for gcc 5.1.
-// - In both of the above cases we are using the gcc compiler. When defining
-// this ourselves on compiler intrinsics, the __is_trivially_copyable()
-// intrinsic is not available on gcc before version 5.1 (see the discussion in
-// https://llvm.org/bugs/show_bug.cgi?id=27538#c1 again), so we must check for
-// that version.
-// - When __is_trivially_copyable() is not available because we are on gcc older
-// than 5.1, we need to fall back to something, so we use __has_trivial_copy()
-// instead based on what was done one-off in bit_cast() previously.
-
-// TODO(crbug.com/554293): Remove this when all platforms have this in the std
-// namespace and it works with gcc as needed.
-#if defined(CR_USE_FALLBACKS_FOR_OLD_EXPERIMENTAL_GLIBCXX) || \
- defined(CR_USE_FALLBACKS_FOR_GCC_WITH_LIBCXX)
-template <typename T>
-struct is_trivially_copyable {
-// TODO(danakj): Remove this when android builders are all using a newer version
-// of gcc, or the android ndk is updated to a newer libc++ that does this for
-// us.
-#if _GNUC_VER >= 501
- static constexpr bool value = __is_trivially_copyable(T);
-#else
- static constexpr bool value =
- __has_trivial_copy(T) && __has_trivial_destructor(T);
-#endif
-};
-#else
-template <class T>
-using is_trivially_copyable = std::is_trivially_copyable<T>;
-#endif
-
-#if defined(__GNUC__) && !defined(__clang__) && __GNUC__ <= 7
-// Workaround for g++7 and earlier family.
-// Due to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80654, without this
-// absl::optional<std::vector<T>> where T is non-copyable causes a compile
-// error. As we know it is not trivially copy constructible, explicitly declare
-// so.
-template <typename T>
-struct is_trivially_copy_constructible
- : std::is_trivially_copy_constructible<T> {};
-
-template <typename... T>
-struct is_trivially_copy_constructible<std::vector<T...>> : std::false_type {};
-#else
-// Otherwise use std::is_trivially_copy_constructible as is.
-template <typename T>
-using is_trivially_copy_constructible = std::is_trivially_copy_constructible<T>;
-#endif
-
-// pdfium::in_place_t is an implementation of std::in_place_t from
-// C++17. A tag type used to request in-place construction in template vararg
-// constructors.
-
-// Specification:
-// https://en.cppreference.com/w/cpp/utility/in_place
-struct in_place_t {};
-constexpr in_place_t in_place = {};
-
-// C++14 implementation of C++17's std::disjunction.
-//
-// Reference: https://en.cppreference.com/w/cpp/types/disjunction
-// Specification: https://wg21.link/meta.logical#itemdecl:2
-template <typename...>
-struct disjunction : std::false_type {};
-
-template <typename B1>
-struct disjunction<B1> : B1 {};
-
-template <typename B1, typename... Bn>
-struct disjunction<B1, Bn...>
- : std::conditional_t<static_cast<bool>(B1::value), B1, disjunction<Bn...>> {
-};
-
} // namespace pdfium
-#undef CR_USE_FALLBACKS_FOR_GCC_WITH_LIBCXX
-#undef CR_USE_FALLBACKS_FOR_OLD_EXPERIMENTAL_GLIBCXX
-
#endif // THIRD_PARTY_BASE_TEMPLATE_UTIL_H_
