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- // Copyright (c) 2012 The Chromium Authors. All rights reserved.
- // Use of this source code is governed by a BSD-style license that can be
- // found in the LICENSE file.
- #ifndef BASE_COMPILER_SPECIFIC_H_
- #define BASE_COMPILER_SPECIFIC_H_
- #include "build/build_config.h"
- #if defined(COMPILER_MSVC) && !defined(__clang__)
- #error "Only clang-cl is supported on Windows, see https://crbug.com/988071"
- #endif
- // This is a wrapper around `__has_cpp_attribute`, which can be used to test for
- // the presence of an attribute. In case the compiler does not support this
- // macro it will simply evaluate to 0.
- //
- // References:
- // https://wg21.link/sd6#testing-for-the-presence-of-an-attribute-__has_cpp_attribute
- // https://wg21.link/cpp.cond#:__has_cpp_attribute
- #if defined(__has_cpp_attribute)
- #define HAS_CPP_ATTRIBUTE(x) __has_cpp_attribute(x)
- #else
- #define HAS_CPP_ATTRIBUTE(x) 0
- #endif
- // A wrapper around `__has_attribute`, similar to HAS_CPP_ATTRIBUTE.
- #if defined(__has_attribute)
- #define HAS_ATTRIBUTE(x) __has_attribute(x)
- #else
- #define HAS_ATTRIBUTE(x) 0
- #endif
- // A wrapper around `__has_builtin`, similar to HAS_CPP_ATTRIBUTE.
- #if defined(__has_builtin)
- #define HAS_BUILTIN(x) __has_builtin(x)
- #else
- #define HAS_BUILTIN(x) 0
- #endif
- // Annotate a function indicating it should not be inlined.
- // Use like:
- // NOINLINE void DoStuff() { ... }
- #if defined(COMPILER_GCC) || defined(__clang__)
- #define NOINLINE __attribute__((noinline))
- #elif defined(COMPILER_MSVC)
- #define NOINLINE __declspec(noinline)
- #else
- #define NOINLINE
- #endif
- #if defined(COMPILER_GCC) && defined(NDEBUG)
- #define ALWAYS_INLINE inline __attribute__((__always_inline__))
- #elif defined(COMPILER_MSVC) && defined(NDEBUG)
- #define ALWAYS_INLINE __forceinline
- #else
- #define ALWAYS_INLINE inline
- #endif
- // Annotate a function indicating it should never be tail called. Useful to make
- // sure callers of the annotated function are never omitted from call-stacks.
- // To provide the complementary behavior (prevent the annotated function from
- // being omitted) look at NOINLINE. Also note that this doesn't prevent code
- // folding of multiple identical caller functions into a single signature. To
- // prevent code folding, see NO_CODE_FOLDING() in base/debug/alias.h.
- // Use like:
- // void NOT_TAIL_CALLED FooBar();
- #if defined(__clang__) && HAS_ATTRIBUTE(not_tail_called)
- #define NOT_TAIL_CALLED __attribute__((not_tail_called))
- #else
- #define NOT_TAIL_CALLED
- #endif
- // Specify memory alignment for structs, classes, etc.
- // Use like:
- // class ALIGNAS(16) MyClass { ... }
- // ALIGNAS(16) int array[4];
- //
- // In most places you can use the C++11 keyword "alignas", which is preferred.
- //
- // But compilers have trouble mixing __attribute__((...)) syntax with
- // alignas(...) syntax.
- //
- // Doesn't work in clang or gcc:
- // struct alignas(16) __attribute__((packed)) S { char c; };
- // Works in clang but not gcc:
- // struct __attribute__((packed)) alignas(16) S2 { char c; };
- // Works in clang and gcc:
- // struct alignas(16) S3 { char c; } __attribute__((packed));
- //
- // There are also some attributes that must be specified *before* a class
- // definition: visibility (used for exporting functions/classes) is one of
- // these attributes. This means that it is not possible to use alignas() with a
- // class that is marked as exported.
- #if defined(COMPILER_MSVC)
- #define ALIGNAS(byte_alignment) __declspec(align(byte_alignment))
- #elif defined(COMPILER_GCC)
- #define ALIGNAS(byte_alignment) __attribute__((aligned(byte_alignment)))
- #endif
- // In case the compiler supports it NO_UNIQUE_ADDRESS evaluates to the C++20
- // attribute [[no_unique_address]]. This allows annotating data members so that
- // they need not have an address distinct from all other non-static data members
- // of its class.
- //
- // References:
- // * https://en.cppreference.com/w/cpp/language/attributes/no_unique_address
- // * https://wg21.link/dcl.attr.nouniqueaddr
- #if HAS_CPP_ATTRIBUTE(no_unique_address)
- #define NO_UNIQUE_ADDRESS [[no_unique_address]]
- #else
- #define NO_UNIQUE_ADDRESS
- #endif
- // Tell the compiler a function is using a printf-style format string.
- // |format_param| is the one-based index of the format string parameter;
- // |dots_param| is the one-based index of the "..." parameter.
- // For v*printf functions (which take a va_list), pass 0 for dots_param.
- // (This is undocumented but matches what the system C headers do.)
- // For member functions, the implicit this parameter counts as index 1.
- #if defined(COMPILER_GCC) || defined(__clang__)
- #define PRINTF_FORMAT(format_param, dots_param) \
- __attribute__((format(printf, format_param, dots_param)))
- #else
- #define PRINTF_FORMAT(format_param, dots_param)
- #endif
- // WPRINTF_FORMAT is the same, but for wide format strings.
- // This doesn't appear to yet be implemented in any compiler.
- // See http://gcc.gnu.org/bugzilla/show_bug.cgi?id=38308 .
- #define WPRINTF_FORMAT(format_param, dots_param)
- // If available, it would look like:
- // __attribute__((format(wprintf, format_param, dots_param)))
- // Sanitizers annotations.
- #if HAS_ATTRIBUTE(no_sanitize)
- #define NO_SANITIZE(what) __attribute__((no_sanitize(what)))
- #endif
- #if !defined(NO_SANITIZE)
- #define NO_SANITIZE(what)
- #endif
- // MemorySanitizer annotations.
- #if defined(MEMORY_SANITIZER) && !BUILDFLAG(IS_NACL)
- #include <sanitizer/msan_interface.h>
- // Mark a memory region fully initialized.
- // Use this to annotate code that deliberately reads uninitialized data, for
- // example a GC scavenging root set pointers from the stack.
- #define MSAN_UNPOISON(p, size) __msan_unpoison(p, size)
- // Check a memory region for initializedness, as if it was being used here.
- // If any bits are uninitialized, crash with an MSan report.
- // Use this to sanitize data which MSan won't be able to track, e.g. before
- // passing data to another process via shared memory.
- #define MSAN_CHECK_MEM_IS_INITIALIZED(p, size) \
- __msan_check_mem_is_initialized(p, size)
- #else // MEMORY_SANITIZER
- #define MSAN_UNPOISON(p, size)
- #define MSAN_CHECK_MEM_IS_INITIALIZED(p, size)
- #endif // MEMORY_SANITIZER
- // DISABLE_CFI_PERF -- Disable Control Flow Integrity for perf reasons.
- #if !defined(DISABLE_CFI_PERF)
- #if defined(__clang__) && defined(OFFICIAL_BUILD)
- #define DISABLE_CFI_PERF __attribute__((no_sanitize("cfi")))
- #else
- #define DISABLE_CFI_PERF
- #endif
- #endif
- // DISABLE_CFI_ICALL -- Disable Control Flow Integrity indirect call checks.
- // Security Note: if you just need to allow calling of dlsym functions use
- // DISABLE_CFI_DLSYM.
- #if !defined(DISABLE_CFI_ICALL)
- #if BUILDFLAG(IS_WIN)
- // Windows also needs __declspec(guard(nocf)).
- #define DISABLE_CFI_ICALL NO_SANITIZE("cfi-icall") __declspec(guard(nocf))
- #else
- #define DISABLE_CFI_ICALL NO_SANITIZE("cfi-icall")
- #endif
- #endif
- #if !defined(DISABLE_CFI_ICALL)
- #define DISABLE_CFI_ICALL
- #endif
- // DISABLE_CFI_DLSYM -- applies DISABLE_CFI_ICALL on platforms where dlsym
- // functions must be called. Retains CFI checks on platforms where loaded
- // modules participate in CFI (e.g. Windows).
- #if !defined(DISABLE_CFI_DLSYM)
- #if BUILDFLAG(IS_WIN)
- // Windows modules register functions when loaded so can be checked by CFG.
- #define DISABLE_CFI_DLSYM
- #else
- #define DISABLE_CFI_DLSYM DISABLE_CFI_ICALL
- #endif
- #endif
- #if !defined(DISABLE_CFI_DLSYM)
- #define DISABLE_CFI_DLSYM
- #endif
- // Macro useful for writing cross-platform function pointers.
- #if !defined(CDECL)
- #if BUILDFLAG(IS_WIN)
- #define CDECL __cdecl
- #else // BUILDFLAG(IS_WIN)
- #define CDECL
- #endif // BUILDFLAG(IS_WIN)
- #endif // !defined(CDECL)
- // Macro for hinting that an expression is likely to be false.
- #if !defined(UNLIKELY)
- #if defined(COMPILER_GCC) || defined(__clang__)
- #define UNLIKELY(x) __builtin_expect(!!(x), 0)
- #else
- #define UNLIKELY(x) (x)
- #endif // defined(COMPILER_GCC)
- #endif // !defined(UNLIKELY)
- #if !defined(LIKELY)
- #if defined(COMPILER_GCC) || defined(__clang__)
- #define LIKELY(x) __builtin_expect(!!(x), 1)
- #else
- #define LIKELY(x) (x)
- #endif // defined(COMPILER_GCC)
- #endif // !defined(LIKELY)
- // Compiler feature-detection.
- // clang.llvm.org/docs/LanguageExtensions.html#has-feature-and-has-extension
- #if defined(__has_feature)
- #define HAS_FEATURE(FEATURE) __has_feature(FEATURE)
- #else
- #define HAS_FEATURE(FEATURE) 0
- #endif
- #if defined(COMPILER_GCC)
- #define PRETTY_FUNCTION __PRETTY_FUNCTION__
- #elif defined(COMPILER_MSVC)
- #define PRETTY_FUNCTION __FUNCSIG__
- #else
- // See https://en.cppreference.com/w/c/language/function_definition#func
- #define PRETTY_FUNCTION __func__
- #endif
- #if !defined(CPU_ARM_NEON)
- #if defined(__arm__)
- #if !defined(__ARMEB__) && !defined(__ARM_EABI__) && !defined(__EABI__) && \
- !defined(__VFP_FP__) && !defined(_WIN32_WCE) && !defined(ANDROID)
- #error Chromium does not support middle endian architecture
- #endif
- #if defined(__ARM_NEON__)
- #define CPU_ARM_NEON 1
- #endif
- #endif // defined(__arm__)
- #endif // !defined(CPU_ARM_NEON)
- #if !defined(HAVE_MIPS_MSA_INTRINSICS)
- #if defined(__mips_msa) && defined(__mips_isa_rev) && (__mips_isa_rev >= 5)
- #define HAVE_MIPS_MSA_INTRINSICS 1
- #endif
- #endif
- #if defined(__clang__) && HAS_ATTRIBUTE(uninitialized)
- // Attribute "uninitialized" disables -ftrivial-auto-var-init=pattern for
- // the specified variable.
- // Library-wide alternative is
- // 'configs -= [ "//build/config/compiler:default_init_stack_vars" ]' in .gn
- // file.
- //
- // See "init_stack_vars" in build/config/compiler/BUILD.gn and
- // http://crbug.com/977230
- // "init_stack_vars" is enabled for non-official builds and we hope to enable it
- // in official build in 2020 as well. The flag writes fixed pattern into
- // uninitialized parts of all local variables. In rare cases such initialization
- // is undesirable and attribute can be used:
- // 1. Degraded performance
- // In most cases compiler is able to remove additional stores. E.g. if memory is
- // never accessed or properly initialized later. Preserved stores mostly will
- // not affect program performance. However if compiler failed on some
- // performance critical code we can get a visible regression in a benchmark.
- // 2. memset, memcpy calls
- // Compiler may replaces some memory writes with memset or memcpy calls. This is
- // not -ftrivial-auto-var-init specific, but it can happen more likely with the
- // flag. It can be a problem if code is not linked with C run-time library.
- //
- // Note: The flag is security risk mitigation feature. So in future the
- // attribute uses should be avoided when possible. However to enable this
- // mitigation on the most of the code we need to be less strict now and minimize
- // number of exceptions later. So if in doubt feel free to use attribute, but
- // please document the problem for someone who is going to cleanup it later.
- // E.g. platform, bot, benchmark or test name in patch description or next to
- // the attribute.
- #define STACK_UNINITIALIZED __attribute__((uninitialized))
- #else
- #define STACK_UNINITIALIZED
- #endif
- // Attribute "no_stack_protector" disables -fstack-protector for the specified
- // function.
- //
- // "stack_protector" is enabled on most POSIX builds. The flag adds a canary
- // to each stack frame, which on function return is checked against a reference
- // canary. If the canaries do not match, it's likely that a stack buffer
- // overflow has occurred, so immediately crashing will prevent exploitation in
- // many cases.
- //
- // In some cases it's desirable to remove this, e.g. on hot functions, or if
- // we have purposely changed the reference canary.
- #if defined(COMPILER_GCC) || defined(__clang__)
- #if HAS_ATTRIBUTE(__no_stack_protector__)
- #define NO_STACK_PROTECTOR __attribute__((__no_stack_protector__))
- #else
- #define NO_STACK_PROTECTOR __attribute__((__optimize__("-fno-stack-protector")))
- #endif
- #else
- #define NO_STACK_PROTECTOR
- #endif
- // The ANALYZER_ASSUME_TRUE(bool arg) macro adds compiler-specific hints
- // to Clang which control what code paths are statically analyzed,
- // and is meant to be used in conjunction with assert & assert-like functions.
- // The expression is passed straight through if analysis isn't enabled.
- //
- // ANALYZER_SKIP_THIS_PATH() suppresses static analysis for the current
- // codepath and any other branching codepaths that might follow.
- #if defined(__clang_analyzer__)
- inline constexpr bool AnalyzerNoReturn() __attribute__((analyzer_noreturn)) {
- return false;
- }
- inline constexpr bool AnalyzerAssumeTrue(bool arg) {
- // AnalyzerNoReturn() is invoked and analysis is terminated if |arg| is
- // false.
- return arg || AnalyzerNoReturn();
- }
- #define ANALYZER_ASSUME_TRUE(arg) ::AnalyzerAssumeTrue(!!(arg))
- #define ANALYZER_SKIP_THIS_PATH() static_cast<void>(::AnalyzerNoReturn())
- #else // !defined(__clang_analyzer__)
- #define ANALYZER_ASSUME_TRUE(arg) (arg)
- #define ANALYZER_SKIP_THIS_PATH()
- #endif // defined(__clang_analyzer__)
- // Use nomerge attribute to disable optimization of merging multiple same calls.
- #if defined(__clang__) && HAS_ATTRIBUTE(nomerge)
- #define NOMERGE [[clang::nomerge]]
- #else
- #define NOMERGE
- #endif
- // Marks a type as being eligible for the "trivial" ABI despite having a
- // non-trivial destructor or copy/move constructor. Such types can be relocated
- // after construction by simply copying their memory, which makes them eligible
- // to be passed in registers. The canonical example is std::unique_ptr.
- //
- // Use with caution; this has some subtle effects on constructor/destructor
- // ordering and will be very incorrect if the type relies on its address
- // remaining constant. When used as a function argument (by value), the value
- // may be constructed in the caller's stack frame, passed in a register, and
- // then used and destructed in the callee's stack frame. A similar thing can
- // occur when values are returned.
- //
- // TRIVIAL_ABI is not needed for types which have a trivial destructor and
- // copy/move constructors, such as base::TimeTicks and other POD.
- //
- // It is also not likely to be effective on types too large to be passed in one
- // or two registers on typical target ABIs.
- //
- // See also:
- // https://clang.llvm.org/docs/AttributeReference.html#trivial-abi
- // https://libcxx.llvm.org/docs/DesignDocs/UniquePtrTrivialAbi.html
- #if defined(__clang__) && HAS_ATTRIBUTE(trivial_abi)
- #define TRIVIAL_ABI [[clang::trivial_abi]]
- #else
- #define TRIVIAL_ABI
- #endif
- // Marks a member function as reinitializing a moved-from variable.
- // See also
- // https://clang.llvm.org/extra/clang-tidy/checks/bugprone-use-after-move.html#reinitialization
- #if defined(__clang__) && HAS_ATTRIBUTE(reinitializes)
- #define REINITIALIZES_AFTER_MOVE [[clang::reinitializes]]
- #else
- #define REINITIALIZES_AFTER_MOVE
- #endif
- // Requires constant initialization. See constinit in C++20. Allows to rely on a
- // variable being initialized before execution, and not requiring a global
- // constructor.
- #if HAS_ATTRIBUTE(require_constant_initialization)
- #define CONSTINIT __attribute__((require_constant_initialization))
- #endif
- #if !defined(CONSTINIT)
- #define CONSTINIT
- #endif
- #if defined(__clang__)
- #define GSL_OWNER [[gsl::Owner]]
- #define GSL_POINTER [[gsl::Pointer]]
- #else
- #define GSL_OWNER
- #define GSL_POINTER
- #endif
- #endif // BASE_COMPILER_SPECIFIC_H_
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