X-Git-Url: http://plrg.eecs.uci.edu/git/?p=folly.git;a=blobdiff_plain;f=folly%2FPortability.h;h=15f393e0be911d2f8eacb252ddc1bad9a362f07b;hp=053b5b1632b57004db715d80be899671c24830a4;hb=1bdec475acac176a9692b6e506564c8c0ccd1984;hpb=a732ef1cd608495f5e0dfafbc7fbfda11fc95ead

diff --git a/folly/Portability.h b/folly/Portability.h
index 053b5b16..15f393e0 100644
--- a/folly/Portability.h
+++ b/folly/Portability.h
@@ -19,6 +19,7 @@
 #include <string.h>
 
 #include <cstddef>
+#include <type_traits>
 
 #include <folly/portability/Config.h>
 
@@ -31,7 +32,74 @@ constexpr bool kHasUnalignedAccess = true;
 #else
 constexpr bool kHasUnalignedAccess = false;
 #endif
-}
+
+namespace portability_detail {
+
+template <typename I, I A, I B>
+using integral_max = std::integral_constant<I, (A < B) ? B : A>;
+
+template <typename I, I A, I... Bs>
+struct integral_sequence_max
+    : integral_max<I, A, integral_sequence_max<I, Bs...>::value> {};
+
+template <typename I, I A>
+struct integral_sequence_max<I, A> : std::integral_constant<I, A> {};
+
+template <typename... Ts>
+using max_alignment = integral_sequence_max<size_t, alignof(Ts)...>;
+
+using max_basic_alignment = max_alignment<
+    std::max_align_t,
+    long double,
+    double,
+    float,
+    long long int,
+    long int,
+    int,
+    short int,
+    bool,
+    char,
+    char16_t,
+    char32_t,
+    wchar_t,
+    std::nullptr_t>;
+} // namespace portability_detail
+
+constexpr size_t max_align_v = portability_detail::max_basic_alignment::value;
+
+// max_align_t is a type which is aligned at least as strictly as the
+// most-aligned basic type (see the specification of std::max_align_t). This
+// implementation exists because 32-bit iOS platforms have a broken
+// std::max_align_t (see below).
+//
+// You should refer to this as `::folly::max_align_t` in portable code, even if
+// you have `using namespace folly;` because C11 defines a global namespace
+// `max_align_t` type.
+//
+// To be certain, we consider every non-void fundamental type specified by the
+// standard. On most platforms `long double` would be enough, but iOS 32-bit
+// has an 8-byte aligned `double` and `long long int` and a 4-byte aligned
+// `long double`.
+//
+// So far we've covered locals and other non-allocated storage, but we also need
+// confidence that allocated storage from `malloc`, `new`, etc will also be
+// suitable for objects with this alignment reuirement.
+//
+// Apple document that their implementation of malloc will issue 16-byte
+// granularity chunks for small allocations (large allocations are page-size
+// granularity and page-aligned). We think that allocated storage will be
+// suitable for these objects based on the following assumptions:
+//
+// 1. 16-byte granularity also means 16-byte aligned.
+// 2. `new` and other allocators follow the `malloc` rules.
+//
+// We also have some anecdotal evidence: we don't see lots of misaligned-storage
+// crashes on 32-bit iOS apps that use `double`.
+//
+// Apple's allocation reference: http://bit.ly/malloc-small
+struct alignas(max_align_v) max_align_t {};
+
+} // namespace folly
 
 // compiler specific attribute translation
 // msvc should come first, so if clang is in msvc mode it gets the right defines
@@ -43,7 +111,7 @@ constexpr bool kHasUnalignedAccess = false;
 #else
 # error Cannot define FOLLY_ALIGNED on this platform
 #endif
-#define FOLLY_ALIGNED_MAX FOLLY_ALIGNED(alignof(std::max_align_t))
+#define FOLLY_ALIGNED_MAX FOLLY_ALIGNED(::folly::max_align_v)
 
 // NOTE: this will only do checking in msvc with versions that support /analyze
 #if _MSC_VER
@@ -101,9 +169,9 @@ constexpr bool kHasUnalignedAccess = false;
 #endif
 
 #if defined(__aarch64__)
-# define FOLLY_A64 1
+# define FOLLY_AARCH64 1
 #else
-# define FOLLY_A64 0
+# define FOLLY_AARCH64 0
 #endif
 
 #if defined (__powerpc64__)
@@ -114,9 +182,9 @@ constexpr bool kHasUnalignedAccess = false;
 
 namespace folly {
 constexpr bool kIsArchAmd64 = FOLLY_X64 == 1;
-constexpr bool kIsArchAArch64 = FOLLY_A64 == 1;
+constexpr bool kIsArchAArch64 = FOLLY_AARCH64 == 1;
 constexpr bool kIsArchPPC64 = FOLLY_PPC64 == 1;
-}
+} // namespace folly
 
 namespace folly {
 
@@ -131,7 +199,7 @@ constexpr bool kIsSanitizeThread = true;
 #else
 constexpr bool kIsSanitizeThread = false;
 #endif
-}
+} // namespace folly
 
 // packing is very ugly in msvc
 #ifdef _MSC_VER
@@ -171,7 +239,7 @@ constexpr bool kIsSanitizeThread = false;
 # define FOLLY_MSVC_DISABLE_WARNING(warningNumber)
 #endif
 
-#ifdef HAVE_SHADOW_LOCAL_WARNINGS
+#ifdef FOLLY_HAVE_SHADOW_LOCAL_WARNINGS
 #define FOLLY_GCC_DISABLE_NEW_SHADOW_WARNINGS        \
   FOLLY_GCC_DISABLE_WARNING("-Wshadow-compatible-local") \
   FOLLY_GCC_DISABLE_WARNING("-Wshadow-local")
@@ -179,18 +247,6 @@ constexpr bool kIsSanitizeThread = false;
 #define FOLLY_GCC_DISABLE_NEW_SHADOW_WARNINGS /* empty */
 #endif
 
-// portable version check for clang
-#ifndef __CLANG_PREREQ
-# if defined __clang__ && defined __clang_major__ && defined __clang_minor__
-/* nolint */
-#  define __CLANG_PREREQ(maj, min) \
-    ((__clang_major__ << 16) + __clang_minor__ >= ((maj) << 16) + (min))
-# else
-/* nolint */
-#  define __CLANG_PREREQ(maj, min) 0
-# endif
-#endif
-
 /* Platform specific TLS support
  * gcc implements __thread
  * msvc implements __declspec(thread)
@@ -257,7 +313,7 @@ constexpr auto kIsDebug = false;
 #else
 constexpr auto kIsDebug = true;
 #endif
-}
+} // namespace folly
 
 // Endianness
 namespace folly {
@@ -272,7 +328,7 @@ constexpr auto kIsLittleEndian = true;
 constexpr auto kIsLittleEndian = __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__;
 #endif
 constexpr auto kIsBigEndian = !kIsLittleEndian;
-}
+} // namespace folly
 
 #ifndef FOLLY_SSE
 # if defined(__SSE4_2__)
@@ -306,7 +362,7 @@ constexpr auto kIsBigEndian = !kIsLittleEndian;
 namespace FOLLY_GFLAGS_NAMESPACE { }
 namespace gflags {
 using namespace FOLLY_GFLAGS_NAMESPACE;
-}  // namespace gflags
+} // namespace gflags
 #endif
 
 // for TARGET_OS_IPHONE
@@ -350,4 +406,31 @@ constexpr auto kMscVer = _MSC_VER;
 constexpr auto kIsWindows = false;
 constexpr auto kMscVer = 0;
 #endif
-}
+} // namespace folly
+
+// Define FOLLY_USE_CPP14_CONSTEXPR to be true if the compiler's C++14
+// constexpr support is "good enough".
+#ifndef FOLLY_USE_CPP14_CONSTEXPR
+#if defined(__clang__)
+#define FOLLY_USE_CPP14_CONSTEXPR __cplusplus >= 201300L
+#elif defined(__GNUC__)
+#define FOLLY_USE_CPP14_CONSTEXPR __cplusplus >= 201304L
+#else
+#define FOLLY_USE_CPP14_CONSTEXPR 0 // MSVC?
+#endif
+#endif
+
+#if FOLLY_USE_CPP14_CONSTEXPR
+#define FOLLY_CPP14_CONSTEXPR constexpr
+#else
+#define FOLLY_CPP14_CONSTEXPR inline
+#endif
+
+#if __cpp_coroutines >= 201703L || (_MSC_VER && _RESUMABLE_FUNCTIONS_SUPPORTED)
+#define FOLLY_HAS_COROUTINES 1
+#endif
+
+// MSVC 2017.5
+#if __cpp_noexcept_function_type >= 201510 || _MSC_FULL_VER >= 191225816
+#define FOLLY_HAVE_NOEXCEPT_FUNCTION_TYPE 1
+#endif