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// Copyright Epic Games, Inc. All Rights Reserved.
#include <zencore/crashhandler.h>
#include <stdio.h>
#include <string.h>
#if ZEN_PLATFORM_WINDOWS
# include <zencore/windows.h>
# include <DbgHelp.h>
#elif ZEN_PLATFORM_LINUX || ZEN_PLATFORM_MAC
# include <execinfo.h>
# include <signal.h>
# include <unistd.h>
#endif
namespace zen {
#if ZEN_PLATFORM_WINDOWS
static LONG WINAPI
CrashExceptionFilter(PEXCEPTION_POINTERS ExceptionInfo)
{
const char* ExceptionName = nullptr;
switch (ExceptionInfo->ExceptionRecord->ExceptionCode)
{
case EXCEPTION_ACCESS_VIOLATION:
ExceptionName = "EXCEPTION_ACCESS_VIOLATION";
break;
case EXCEPTION_ILLEGAL_INSTRUCTION:
ExceptionName = "EXCEPTION_ILLEGAL_INSTRUCTION";
break;
case EXCEPTION_INT_DIVIDE_BY_ZERO:
ExceptionName = "EXCEPTION_INT_DIVIDE_BY_ZERO";
break;
case EXCEPTION_ARRAY_BOUNDS_EXCEEDED:
ExceptionName = "EXCEPTION_ARRAY_BOUNDS_EXCEEDED";
break;
case EXCEPTION_FLT_DIVIDE_BY_ZERO:
ExceptionName = "EXCEPTION_FLT_DIVIDE_BY_ZERO";
break;
default:
return EXCEPTION_CONTINUE_SEARCH;
}
fprintf(stderr,
"\n*** FATAL: %s at address 0x%p (pid %lu)\n",
ExceptionName,
ExceptionInfo->ExceptionRecord->ExceptionAddress,
GetCurrentProcessId());
// Capture backtrace from the exception context using StackWalk64 so we get
// the actual crash site rather than the exception dispatch frames
HANDLE Process = GetCurrentProcess();
HANDLE Thread = GetCurrentThread();
// SymInitialize is safe to call if already initialized — it returns FALSE
// but existing state remains valid for SymFromAddr calls
SymInitialize(Process, NULL, TRUE);
CONTEXT Context = *ExceptionInfo->ContextRecord;
STACKFRAME64 StackFrame;
memset(&StackFrame, 0, sizeof(StackFrame));
# if ZEN_ARCH_X64
DWORD MachineType = IMAGE_FILE_MACHINE_AMD64;
StackFrame.AddrPC.Offset = Context.Rip;
StackFrame.AddrPC.Mode = AddrModeFlat;
StackFrame.AddrFrame.Offset = Context.Rbp;
StackFrame.AddrFrame.Mode = AddrModeFlat;
StackFrame.AddrStack.Offset = Context.Rsp;
StackFrame.AddrStack.Mode = AddrModeFlat;
# elif ZEN_ARCH_ARM64
DWORD MachineType = IMAGE_FILE_MACHINE_ARM64;
StackFrame.AddrPC.Offset = Context.Pc;
StackFrame.AddrPC.Mode = AddrModeFlat;
StackFrame.AddrFrame.Offset = Context.Fp;
StackFrame.AddrFrame.Mode = AddrModeFlat;
StackFrame.AddrStack.Offset = Context.Sp;
StackFrame.AddrStack.Mode = AddrModeFlat;
# endif
char SymbolBuffer[sizeof(SYMBOL_INFO) + 1024];
SYMBOL_INFO* Symbol = (SYMBOL_INFO*)SymbolBuffer;
Symbol->SizeOfStruct = sizeof(SYMBOL_INFO);
Symbol->MaxNameLen = 1023;
fprintf(stderr, "Backtrace:\n");
for (int FrameIndex = 0; FrameIndex < 64; ++FrameIndex)
{
if (!StackWalk64(MachineType, Process, Thread, &StackFrame, &Context, NULL, SymFunctionTableAccess64, SymGetModuleBase64, NULL))
{
break;
}
DWORD64 Address = StackFrame.AddrPC.Offset;
if (Address == 0)
{
break;
}
DWORD64 Displacement = 0;
if (SymFromAddr(Process, Address, &Displacement, Symbol))
{
fprintf(stderr,
" #%-2d %s+0x%llx [0x%llx]\n",
FrameIndex,
Symbol->Name,
(unsigned long long)Displacement,
(unsigned long long)Address);
}
else
{
fprintf(stderr, " #%-2d [0x%llx]\n", FrameIndex, (unsigned long long)Address);
}
}
fprintf(stderr, "\n");
fflush(stderr);
return EXCEPTION_CONTINUE_SEARCH;
}
void
InstallCrashHandler()
{
SetUnhandledExceptionFilter(CrashExceptionFilter);
}
#elif ZEN_PLATFORM_LINUX || ZEN_PLATFORM_MAC
// Async-signal-safe helper: write a decimal number to a file descriptor
static void
WriteDecimal(int Fd, unsigned long Value)
{
char Buffer[20];
int Pos = sizeof(Buffer);
if (Value == 0)
{
Buffer[--Pos] = '0';
}
else
{
while (Value > 0)
{
Buffer[--Pos] = '0' + (char)(Value % 10);
Value /= 10;
}
}
write(Fd, Buffer + Pos, sizeof(Buffer) - Pos);
}
static void
CrashSignalHandler(int Signal)
{
// Note: backtrace/backtrace_symbols_fd are not strictly async-signal-safe
// (glibc's backtrace may call malloc internally), but they are widely used
// in signal handlers in practice. This is best-effort.
const char* SignalName = "Unknown signal";
switch (Signal)
{
case SIGSEGV:
SignalName = "SIGSEGV";
break;
case SIGABRT:
SignalName = "SIGABRT";
break;
case SIGFPE:
SignalName = "SIGFPE";
break;
case SIGBUS:
SignalName = "SIGBUS";
break;
case SIGILL:
SignalName = "SIGILL";
break;
}
write(STDERR_FILENO, "\n*** FATAL: Caught ", 19);
write(STDERR_FILENO, SignalName, strlen(SignalName));
write(STDERR_FILENO, " (pid ", 6);
WriteDecimal(STDERR_FILENO, (unsigned long)getpid());
write(STDERR_FILENO, ")\nBacktrace:\n", 13);
void* Frames[64];
int FrameCount = backtrace(Frames, 64);
backtrace_symbols_fd(Frames, FrameCount, STDERR_FILENO);
write(STDERR_FILENO, "\n", 1);
// Re-raise with default handler so the process generates a core dump
// and terminates with the correct exit status
signal(Signal, SIG_DFL);
raise(Signal);
}
void
InstallCrashHandler()
{
struct sigaction Action;
memset(&Action, 0, sizeof(Action));
Action.sa_handler = CrashSignalHandler;
Action.sa_flags = SA_RESETHAND; // one-shot: auto-reset to default after firing
sigemptyset(&Action.sa_mask);
sigaction(SIGSEGV, &Action, nullptr);
sigaction(SIGABRT, &Action, nullptr);
sigaction(SIGFPE, &Action, nullptr);
sigaction(SIGBUS, &Action, nullptr);
sigaction(SIGILL, &Action, nullptr);
}
#endif
} // namespace zen
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