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TMessagesProj/jni/voip/webrtc/base/immediate_crash.h

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+// Copyright 2019 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_IMMEDIATE_CRASH_H_
+#define BASE_IMMEDIATE_CRASH_H_
+
+#include "build/build_config.h"
+
+// Crashes in the fastest possible way with no attempt at logging.
+// There are several constraints; see http://crbug.com/664209 for more context.
+//
+// - TRAP_SEQUENCE_() must be fatal. It should not be possible to ignore the
+//   resulting exception or simply hit 'continue' to skip over it in a debugger.
+// - Different instances of TRAP_SEQUENCE_() must not be folded together, to
+//   ensure crash reports are debuggable. Unlike __builtin_trap(), asm volatile
+//   blocks will not be folded together.
+//   Note: TRAP_SEQUENCE_() previously required an instruction with a unique
+//   nonce since unlike clang, GCC folds together identical asm volatile
+//   blocks.
+// - TRAP_SEQUENCE_() must produce a signal that is distinct from an invalid
+//   memory access.
+// - TRAP_SEQUENCE_() must be treated as a set of noreturn instructions.
+//   __builtin_unreachable() is used to provide that hint here. clang also uses
+//   this as a heuristic to pack the instructions in the function epilogue to
+//   improve code density.
+//
+// Additional properties that are nice to have:
+// - TRAP_SEQUENCE_() should be as compact as possible.
+// - The first instruction of TRAP_SEQUENCE_() should not change, to avoid
+//   shifting crash reporting clusters. As a consequence of this, explicit
+//   assembly is preferred over intrinsics.
+//   Note: this last bullet point may no longer be true, and may be removed in
+//   the future.
+
+// Note: TRAP_SEQUENCE Is currently split into two macro helpers due to the fact
+// that clang emits an actual instruction for __builtin_unreachable() on certain
+// platforms (see https://crbug.com/958675). In addition, the int3/bkpt/brk will
+// be removed in followups, so splitting it up like this now makes it easy to
+// land the followups.
+
+#if defined(COMPILER_GCC)
+
+#if defined(OS_NACL)
+
+// Crash report accuracy is not guaranteed on NaCl.
+#define TRAP_SEQUENCE1_() __builtin_trap()
+#define TRAP_SEQUENCE2_() asm volatile("")
+
+#elif defined(ARCH_CPU_X86_FAMILY)
+
+// TODO(https://crbug.com/958675): In theory, it should be possible to use just
+// int3. However, there are a number of crashes with SIGILL as the exception
+// code, so it seems likely that there's a signal handler that allows execution
+// to continue after SIGTRAP.
+#define TRAP_SEQUENCE1_() asm volatile("int3")
+
+#if defined(OS_MACOSX)
+// Intentionally empty: __builtin_unreachable() is always part of the sequence
+// (see IMMEDIATE_CRASH below) and already emits a ud2 on Mac.
+#define TRAP_SEQUENCE2_() asm volatile("")
+#else
+#define TRAP_SEQUENCE2_() asm volatile("ud2")
+#endif  // defined(OS_MACOSX)
+
+#elif defined(ARCH_CPU_ARMEL)
+
+// bkpt will generate a SIGBUS when running on armv7 and a SIGTRAP when running
+// as a 32 bit userspace app on arm64. There doesn't seem to be any way to
+// cause a SIGTRAP from userspace without using a syscall (which would be a
+// problem for sandboxing).
+// TODO(https://crbug.com/958675): Remove bkpt from this sequence.
+#define TRAP_SEQUENCE1_() asm volatile("bkpt #0")
+#define TRAP_SEQUENCE2_() asm volatile("udf #0")
+
+#elif defined(ARCH_CPU_ARM64)
+
+// This will always generate a SIGTRAP on arm64.
+// TODO(https://crbug.com/958675): Remove brk from this sequence.
+#define TRAP_SEQUENCE1_() asm volatile("brk #0")
+#define TRAP_SEQUENCE2_() asm volatile("hlt #0")
+
+#else
+
+// Crash report accuracy will not be guaranteed on other architectures, but at
+// least this will crash as expected.
+#define TRAP_SEQUENCE1_() __builtin_trap()
+#define TRAP_SEQUENCE2_() asm volatile("")
+
+#endif  // ARCH_CPU_*
+
+#elif defined(COMPILER_MSVC)
+
+#if !defined(__clang__)
+
+// MSVC x64 doesn't support inline asm, so use the MSVC intrinsic.
+#define TRAP_SEQUENCE1_() __debugbreak()
+#define TRAP_SEQUENCE2_()
+
+#elif defined(ARCH_CPU_ARM64)
+
+// Windows ARM64 uses "BRK #F000" as its breakpoint instruction, and
+// __debugbreak() generates that in both VC++ and clang.
+#define TRAP_SEQUENCE1_() __debugbreak()
+// Intentionally empty: __builtin_unreachable() is always part of the sequence
+// (see IMMEDIATE_CRASH below) and already emits a ud2 on Win64,
+// https://crbug.com/958373
+#define TRAP_SEQUENCE2_() __asm volatile("")
+
+#else
+
+#define TRAP_SEQUENCE1_() asm volatile("int3")
+#define TRAP_SEQUENCE2_() asm volatile("ud2")
+
+#endif  // __clang__
+
+#else
+
+#error No supported trap sequence!
+
+#endif  // COMPILER_GCC
+
+#define TRAP_SEQUENCE_() \
+  do {                   \
+    TRAP_SEQUENCE1_();   \
+    TRAP_SEQUENCE2_();   \
+  } while (false)
+
+// CHECK() and the trap sequence can be invoked from a constexpr function.
+// This could make compilation fail on GCC, as it forbids directly using inline
+// asm inside a constexpr function. However, it allows calling a lambda
+// expression including the same asm.
+// The side effect is that the top of the stacktrace will not point to the
+// calling function, but to this anonymous lambda. This is still useful as the
+// full name of the lambda will typically include the name of the function that
+// calls CHECK() and the debugger will still break at the right line of code.
+#if !defined(COMPILER_GCC)
+
+#define WRAPPED_TRAP_SEQUENCE_() TRAP_SEQUENCE_()
+
+#else
+
+#define WRAPPED_TRAP_SEQUENCE_() \
+  do {                           \
+    [] { TRAP_SEQUENCE_(); }();  \
+  } while (false)
+
+#endif  // !defined(COMPILER_GCC)
+
+#if defined(__clang__) || defined(COMPILER_GCC)
+
+// __builtin_unreachable() hints to the compiler that this is noreturn and can
+// be packed in the function epilogue.
+#define IMMEDIATE_CRASH()     \
+  ({                          \
+    WRAPPED_TRAP_SEQUENCE_(); \
+    __builtin_unreachable();  \
+  })
+
+#else
+
+// This is supporting non-chromium user of logging.h to build with MSVC, like
+// pdfium. On MSVC there is no __builtin_unreachable().
+#define IMMEDIATE_CRASH() WRAPPED_TRAP_SEQUENCE_()
+
+#endif  // defined(__clang__) || defined(COMPILER_GCC)
+
+#endif  // BASE_IMMEDIATE_CRASH_H_