text: // 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)
  
  // Macros for suppressing and disabling warnings on MSVC.
  //
  // Warning numbers are enumerated at:
  // http://msdn.microsoft.com/en-us/library/8x5x43k7(VS.80).aspx
  //
  // The warning pragma:
  // http://msdn.microsoft.com/en-us/library/2c8f766e(VS.80).aspx
  //
  // Using __pragma instead of #pragma inside macros:
  // http://msdn.microsoft.com/en-us/library/d9x1s805.aspx
  
  // MSVC_PUSH_DISABLE_WARNING pushes |n| onto a stack of warnings to be disabled.
  // The warning remains disabled until popped by MSVC_POP_WARNING.
  #define MSVC_PUSH_DISABLE_WARNING(n) __pragma(warning(push)) \
                                       __pragma(warning(disable:n))
  
  // Pop effects of innermost MSVC_PUSH_* macro.
  #define MSVC_POP_WARNING() __pragma(warning(pop))
  
  #else  // Not MSVC
  
  #define MSVC_PUSH_DISABLE_WARNING(n)
  #define MSVC_POP_WARNING()
  #define MSVC_DISABLE_OPTIMIZE()
  #define MSVC_ENABLE_OPTIMIZE()
  
  #endif  // COMPILER_MSVC
  
  // These macros can be helpful when investigating compiler bugs or when
  // investigating issues in local optimized builds, by temporarily disabling
  // optimizations for a single function or file. These macros should never be
  // used to permanently work around compiler bugs or other mysteries, and should
  // not be used in landed changes.
  #if !defined(OFFICIAL_BUILD)
  #if defined(__clang__)
  #define DISABLE_OPTIMIZE() __pragma(clang optimize off)
  #define ENABLE_OPTIMIZE() __pragma(clang optimize on)
  #elif defined(COMPILER_MSVC)
  #define DISABLE_OPTIMIZE() __pragma(optimize("", off))
  #define ENABLE_OPTIMIZE() __pragma(optimize("", on))
  #else
  // These macros are not currently available for other compiler options.
  #endif
  // These macros are not available in official builds.
  #endif  // !defined(OFFICIAL_BUILD)
  
  // Annotate a variable indicating it's ok if the variable is not used.
  // (Typically used to silence a compiler warning when the assignment
  // is important for some other reason.)
  // Use like:
  //   int x = ...;
  //   ALLOW_UNUSED_LOCAL(x);
  #define ALLOW_UNUSED_LOCAL(x) (void)x
  
  // Annotate a typedef or function indicating it's ok if it's not used.
  // Use like:
  //   typedef Foo Bar ALLOW_UNUSED_TYPE;
  #if defined(COMPILER_GCC) || defined(__clang__)
  #define ALLOW_UNUSED_TYPE __attribute__((unused))
  #else
  #define ALLOW_UNUSED_TYPE
  #endif
  
  // Annotate a function indicating it should not be inlined.
  // Use like:
  //   NOINLINE void DoStuff() { ... }
  #if defined(COMPILER_GCC)
  #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
  
  // 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
  
  // Annotate a function indicating the caller must examine the return value.
  // Use like:
  //   int foo() WARN_UNUSED_RESULT;
  // To explicitly ignore a result, see |ignore_result()| in base/macros.h.
  #undef WARN_UNUSED_RESULT
  #if defined(COMPILER_GCC) || defined(__clang__)
  #define WARN_UNUSED_RESULT __attribute__((warn_unused_result))
  #else
  #define WARN_UNUSED_RESULT
  #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 defined(__has_attribute)
  #if __has_attribute(no_sanitize)
  #define NO_SANITIZE(what) __attribute__((no_sanitize(what)))
  #endif
  #endif
  #if !defined(NO_SANITIZE)
  #define NO_SANITIZE(what)
  #endif
  
  // MemorySanitizer annotations.
  #if defined(MEMORY_SANITIZER) && !defined(OS_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
  
  // Macro useful for writing cross-platform function pointers.
  #if !defined(CDECL)
  #if defined(OS_WIN)
  #define CDECL __cdecl
  #else  // defined(OS_WIN)
  #define CDECL
  #endif  // defined(OS_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
  
  // Macro for telling -Wimplicit-fallthrough that a fallthrough is intentional.
  #if defined(__clang__)
  #define FALLTHROUGH [[clang::fallthrough]]
  #else
  #define FALLTHROUGH
  #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
  
  #endif  // BASE_COMPILER_SPECIFIC_H_
  