自制一个c++ log库-part4

1. 支持打印异常堆栈

   为了能捕获到异常，考虑使用

   __try
   {}
   __except
   {}

   为了防止异常信息丢失，考虑直接写入文件，而不是存入缓存队列等待另一个线程提取再写日志。

   __except里可以拿到exception的结构体，看起来试这样

   __except (GetExceptionInformation())

   GetExceptionInformation 是个宏，能获取_EXCEPTION_POINTERS* ，声明如下：

   typedef struct _EXCEPTION_POINTERS {
       PEXCEPTION_RECORD ExceptionRecord;
       PCONTEXT ContextRecord;
   } EXCEPTION_POINTERS, *PEXCEPTION_POINTERS; 

   其中PEXCEPTION_RECORD 声明如下：

   typedef struct _EXCEPTION_RECORD {
       DWORD    ExceptionCode;
       DWORD ExceptionFlags;
       struct _EXCEPTION_RECORD *ExceptionRecord;
       PVOID ExceptionAddress;
       DWORD NumberParameters;
       ULONG_PTR ExceptionInformation[EXCEPTION_MAXIMUM_PARAMETERS];
       } EXCEPTION_RECORD;

   可以看到里面可以获取到ExceptionCode ，类型是DWORD ，通过这个code可以获取到简单的错误信息：

   const char* Log4Cpp::LogFile::getExcepMsg(const DWORD& code)
   {
   	switch (code) {
   	case EXCEPTION_ACCESS_VIOLATION:         return "EXCEPTION_ACCESS_VIOLATION";
   	case EXCEPTION_ARRAY_BOUNDS_EXCEEDED:    return "EXCEPTION_ARRAY_BOUNDS_EXCEEDED";
   	case EXCEPTION_BREAKPOINT:               return "EXCEPTION_BREAKPOINT";
   	case EXCEPTION_DATATYPE_MISALIGNMENT:    return "EXCEPTION_DATATYPE_MISALIGNMENT";
   	case EXCEPTION_FLT_DENORMAL_OPERAND:     return "EXCEPTION_FLT_DENORMAL_OPERAND";
   	case EXCEPTION_FLT_DIVIDE_BY_ZERO:       return "EXCEPTION_FLT_DIVIDE_BY_ZERO";
   	case EXCEPTION_FLT_INEXACT_RESULT:       return "EXCEPTION_FLT_INEXACT_RESULT";
   	case EXCEPTION_FLT_INVALID_OPERATION:    return "EXCEPTION_FLT_INVALID_OPERATION";
   	case EXCEPTION_FLT_OVERFLOW:             return "EXCEPTION_FLT_OVERFLOW";
   	case EXCEPTION_FLT_STACK_CHECK:          return "EXCEPTION_FLT_STACK_CHECK";
   	case EXCEPTION_FLT_UNDERFLOW:            return "EXCEPTION_FLT_UNDERFLOW";
   	case EXCEPTION_ILLEGAL_INSTRUCTION:      return "EXCEPTION_ILLEGAL_INSTRUCTION";
   	case EXCEPTION_IN_PAGE_ERROR:            return "EXCEPTION_IN_PAGE_ERROR";
   	case EXCEPTION_INT_DIVIDE_BY_ZERO:       return "EXCEPTION_INT_DIVIDE_BY_ZERO";
   	case EXCEPTION_INT_OVERFLOW:             return "EXCEPTION_INT_OVERFLOW";
   	case EXCEPTION_INVALID_DISPOSITION:      return "EXCEPTION_INVALID_DISPOSITION";
   	case EXCEPTION_NONCONTINUABLE_EXCEPTION: return "EXCEPTION_NONCONTINUABLE_EXCEPTION";
   	case EXCEPTION_PRIV_INSTRUCTION:         return "EXCEPTION_PRIV_INSTRUCTION";
   	case EXCEPTION_SINGLE_STEP:              return "EXCEPTION_SINGLE_STEP";
   	case EXCEPTION_STACK_OVERFLOW:           return "EXCEPTION_STACK_OVERFLOW";
   	default: return "UNKNOWN EXCEPTION";
   	}
   }

   另外_EXCEPTION_POINTER 还有个上下文： ContextRecord ，堆栈就主要从这个上下文来获取：

   LONG __stdcall Log4Cpp::LogFile::LogException(_EXCEPTION_POINTERS* exceptionInfo)
   {
   	FILE* pFile = fopen(LOG_ERROR_FILE_Path, "at");
   	if (!pFile)
   		return EXCEPTION_EXECUTE_HANDLER;
   
   	//write log's head
   	SYSTEMTIME systime;
   	GetLocalTime(&systime);
   	fprintf(pFile, "%hu-%02hu-%02hu %02hu:%02hu:%02hu.%03hu Exception occured, code: [0x%x], info: %s\n", systime.wYear, systime.wMonth, systime.wDay, systime.wHour, systime.wMinute, systime.wSecond, systime.wMilliseconds, exceptionInfo->ExceptionRecord->ExceptionCode, getExcepMsg(exceptionInfo->ExceptionRecord->ExceptionCode));
   
   	CONTEXT* ctx = exceptionInfo->ContextRecord;
   	BOOL    result;
   	HANDLE  process;
   	HANDLE  thread;
   	HMODULE hModule;
   
   	STACKFRAME64        stack;
   	ULONG               frame;
   	DWORD64             displacement;
   
   	DWORD disp;
   	IMAGEHLP_LINE64* line;
   
   	char buffer[sizeof(SYMBOL_INFO) + MAX_SYM_NAME * sizeof(TCHAR)];
   	char name[MAX_NAME_LEN];
   	char module[MAX_NAME_LEN];
   	PSYMBOL_INFO pSymbol = (PSYMBOL_INFO)buffer;
   
   	// On x64, StackWalk64 modifies the context record, that could
   	// cause crashes, so we create a copy to prevent it
   	CONTEXT ctxCopy;
   	memcpy(&ctxCopy, ctx, sizeof(CONTEXT));
   
   	memset(&stack, 0, sizeof(STACKFRAME64));
   
   	process = GetCurrentProcess();
   	thread = GetCurrentThread();
   	displacement = 0;
   #if !defined(_M_AMD64)
   	stack.AddrPC.Offset = (*ctx).Eip;
   	stack.AddrPC.Mode = AddrModeFlat;
   	stack.AddrStack.Offset = (*ctx).Esp;
   	stack.AddrStack.Mode = AddrModeFlat;
   	stack.AddrFrame.Offset = (*ctx).Ebp;
   	stack.AddrFrame.Mode = AddrModeFlat;
   #endif
   
   	SymInitialize(process, NULL, TRUE); //load symbols
   
   	for (frame = 0; frame < 10; frame++)
   	{
   		//get next call from stack
   		result = StackWalk64
   		(
   #if defined(_M_AMD64)
   			IMAGE_FILE_MACHINE_AMD64
   #else
   			IMAGE_FILE_MACHINE_I386
   #endif
   			,
   			process,
   			thread,
   			&stack,
   			&ctxCopy,
   			NULL,
   			SymFunctionTableAccess64,
   			SymGetModuleBase64,
   			NULL
   		);
   
   		if (!result)
   			break;
   
   		//get symbol name for address
   		pSymbol->SizeOfStruct = sizeof(SYMBOL_INFO);
   		pSymbol->MaxNameLen = MAX_SYM_NAME;
   		SymFromAddr(process, (ULONG64)stack.AddrPC.Offset, &displacement, pSymbol);
   
   		line = (IMAGEHLP_LINE64*)malloc(sizeof(IMAGEHLP_LINE64));
   		if (!line)
   			return EXCEPTION_EXECUTE_HANDLER;
   
   		line->SizeOfStruct = sizeof(IMAGEHLP_LINE64);
   
   		//try to get line
   		if (SymGetLineFromAddr64(process, stack.AddrPC.Offset, &disp, line))
   		{
   			fprintf(pFile, "\tat %s():%lu\n", pSymbol->Name, line->LineNumber);
   		}
   		else
   		{
   			//failed to get line
   			hModule = NULL;
   			lstrcpyA(module, "");
   			GetModuleHandleEx(GET_MODULE_HANDLE_EX_FLAG_FROM_ADDRESS | GET_MODULE_HANDLE_EX_FLAG_UNCHANGED_REFCOUNT, (LPCTSTR)(stack.AddrPC.Offset), &hModule);
   
   			//at least print module name
   			if (hModule != NULL)
   				GetModuleFileNameA(hModule, module, MAX_NAME_LEN);
   
   			if (strcmp(module, "") != 0)
   				fprintf(pFile, "\tat %s %s()\n", module, pSymbol->Name);
   		}
   
   		free(line);
   		line = NULL;
   	}
   
   	fflush(pFile);
   	fclose(pFile);
   
   	return EXCEPTION_EXECUTE_HANDLER;
   }

   最后，只要把Log4Cpp::LogFile::LogException 传入__except，即可在捕获后调用处理函数：

   __try
   {
   		...
   }
   __except (Log4Cpp::LogFile::LogException(GetExceptionInformation()))
   {
   		...
   }

完整的代码：
Log4Cpp.zip