如何从 GetLastError ()返回的错误代码中获取错误消息？

小开

FormatMessage 将把 GetLastError的整数返回转换为文本消息。

小开

通常，需要使用 FormatMessage将 Win32错误代码转换为文本。

来自 MSDN 文件:

格式化消息字符串需要消息定义为消息定义可以输入从传递到它可以来自一条消息已加载的模块。或者调用者可以请求功能，以搜寻系统的消息表资源消息定义。该函数查找消息中的消息定义基于消息的表资源标识符和语言标识符。函数复制格式化的消息文本到输出缓冲区, 处理任何嵌入式插入如果需要的话。

格式信息声明:

DWORD WINAPI FormatMessage(
__in      DWORD dwFlags,
__in_opt  LPCVOID lpSource,
__in      DWORD dwMessageId, // your error code
__in      DWORD dwLanguageId,
__out     LPTSTR lpBuffer,
__in      DWORD nSize,
__in_opt  va_list *Arguments
);

小开

MSDN 有一些示例代码演示如何同时使用 FormatMessage()和 GetLastError(): 检索最后错误代码

小开

更新(11/2017)以考虑一些意见。

简单的例子:

wchar_t buf[256];
FormatMessageW(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
NULL, GetLastError(), MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
buf, (sizeof(buf) / sizeof(wchar_t)), NULL);

小开

//Returns the last Win32 error, in string format. Returns an empty string if there is no error.
std::string GetLastErrorAsString()
{
//Get the error message ID, if any.
DWORD errorMessageID = ::GetLastError();
if(errorMessageID == 0) {
return std::string(); //No error message has been recorded
}
    

LPSTR messageBuffer = nullptr;


//Ask Win32 to give us the string version of that message ID.
//The parameters we pass in, tell Win32 to create the buffer that holds the message for us (because we don't yet know how long the message string will be).
size_t size = FormatMessageA(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
NULL, errorMessageID, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT), (LPSTR)&messageBuffer, 0, NULL);
    

//Copy the error message into a std::string.
std::string message(messageBuffer, size);
    

//Free the Win32's string's buffer.
LocalFree(messageBuffer);
            

return message;
}

小开

如果使用 c # ，可以使用以下代码:

using System.Runtime.InteropServices;


public static class WinErrors
{
#region definitions
[DllImport("kernel32.dll", SetLastError = true)]
static extern IntPtr LocalFree(IntPtr hMem);


[DllImport("kernel32.dll", SetLastError = true)]
static extern int FormatMessage(FormatMessageFlags dwFlags, IntPtr lpSource, uint dwMessageId, uint dwLanguageId, ref IntPtr lpBuffer, uint nSize, IntPtr Arguments);


[Flags]
private enum FormatMessageFlags : uint
{
FORMAT_MESSAGE_ALLOCATE_BUFFER = 0x00000100,
FORMAT_MESSAGE_IGNORE_INSERTS = 0x00000200,
FORMAT_MESSAGE_FROM_SYSTEM = 0x00001000,
FORMAT_MESSAGE_ARGUMENT_ARRAY = 0x00002000,
FORMAT_MESSAGE_FROM_HMODULE = 0x00000800,
FORMAT_MESSAGE_FROM_STRING = 0x00000400,
}
#endregion


/// <summary>
/// Gets a user friendly string message for a system error code
/// </summary>
/// <param name="errorCode">System error code</param>
/// <returns>Error string</returns>
public static string GetSystemMessage(int errorCode)
{
try
{
IntPtr lpMsgBuf = IntPtr.Zero;


int dwChars = FormatMessage(
FormatMessageFlags.FORMAT_MESSAGE_ALLOCATE_BUFFER | FormatMessageFlags.FORMAT_MESSAGE_FROM_SYSTEM | FormatMessageFlags.FORMAT_MESSAGE_IGNORE_INSERTS,
IntPtr.Zero,
(uint) errorCode,
0, // Default language
ref lpMsgBuf,
0,
IntPtr.Zero);
if (dwChars == 0)
{
// Handle the error.
int le = Marshal.GetLastWin32Error();
return "Unable to get error code string from System - Error " + le.ToString();
}


string sRet = Marshal.PtrToStringAnsi(lpMsgBuf);


// Free the buffer.
lpMsgBuf = LocalFree(lpMsgBuf);
return sRet;
}
catch (Exception e)
{
return "Unable to get error code string from System -> " + e.ToString();
}
}
}

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void WinErrorCodeToString(DWORD ErrorCode, string& Message)
{
char* locbuffer = NULL;
DWORD count = FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER, NULL, ErrorCode,
0, (LPSTR)&locbuffer, 0, nullptr);
if (locbuffer)
{
if (count)
{
int c;
int back = 0;
//
// strip any trailing "\r\n"s and replace by a single "\n"
//
while (((c = *CharPrevA(locbuffer, locbuffer + count)) == '\r') ||
(c == '\n')) {
count--;
back++;
}


if (back) {
locbuffer[count++] = '\n';
locbuffer[count] = '\0';
}


Message = "Error: ";
Message += locbuffer;
}
LocalFree(locbuffer);
}
else
{
Message = "Unknown error code: " + to_string(ErrorCode);
}
}

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如果您需要支持 MBCS 和 Unicode，C64先生的回答是不够的。缓冲区必须声明为 TCHAR，并强制转换为 LPTSTR。请注意，此代码不处理 Microsoft 附加到错误消息中的恼人的换行符。

CString FormatErrorMessage(DWORD ErrorCode)
{
TCHAR   *pMsgBuf = NULL;
DWORD   nMsgLen = FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER |
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
NULL, ErrorCode, MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
reinterpret_cast<LPTSTR>(&pMsgBuf), 0, NULL);
if (!nMsgLen)
return _T("FormatMessage fail");
CString sMsg(pMsgBuf, nMsgLen);
LocalFree(pMsgBuf);
return sMsg;
}

此外，为了简洁起见，我发现下面的方法很有用:

CString GetLastErrorString()
{
return FormatErrorMessage(GetLastError());
}

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GetLastError 返回一个数值错误代码。要获得描述性错误消息(例如，向用户显示) ，可以调用格式信息:

// This functions fills a caller-defined character buffer (pBuffer)
// of max length (cchBufferLength) with the human-readable error message
// for a Win32 error code (dwErrorCode).
//
// Returns TRUE if successful, or FALSE otherwise.
// If successful, pBuffer is guaranteed to be NUL-terminated.
// On failure, the contents of pBuffer are undefined.
BOOL GetErrorMessage(DWORD dwErrorCode, LPTSTR pBuffer, DWORD cchBufferLength)
{
if (cchBufferLength == 0)
{
return FALSE;
}


DWORD cchMsg = FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS,
NULL,  /* (not used with FORMAT_MESSAGE_FROM_SYSTEM) */
dwErrorCode,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
pBuffer,
cchBufferLength,
NULL);
return (cchMsg > 0);
}

在 C + + 中，可以通过使用 std: : string 类大大简化接口:

#include <Windows.h>
#include <system_error>
#include <memory>
#include <string>
typedef std::basic_string<TCHAR> String;


String GetErrorMessage(DWORD dwErrorCode)
{
LPTSTR psz{ nullptr };
const DWORD cchMsg = FormatMessage(FORMAT_MESSAGE_FROM_SYSTEM
| FORMAT_MESSAGE_IGNORE_INSERTS
| FORMAT_MESSAGE_ALLOCATE_BUFFER,
NULL, // (not used with FORMAT_MESSAGE_FROM_SYSTEM)
dwErrorCode,
MAKELANGID(LANG_NEUTRAL, SUBLANG_DEFAULT),
reinterpret_cast<LPTSTR>(&psz),
0,
NULL);
if (cchMsg > 0)
{
// Assign buffer to smart pointer with custom deleter so that memory gets released
// in case String's c'tor throws an exception.
auto deleter = [](void* p) { ::LocalFree(p); };
std::unique_ptr<TCHAR, decltype(deleter)> ptrBuffer(psz, deleter);
return String(ptrBuffer.get(), cchMsg);
}
else
{
auto error_code{ ::GetLastError() };
throw std::system_error( error_code, std::system_category(),
"Failed to retrieve error message string.");
}
}

注意: 这些函数也适用于 HResult T 值。只需将第一个参数从 DWORDdwErrorCode 更改为 HResult ThResult。代码的其余部分可以保持不变。

与现有答案相比，这些实施工作提供了以下改进:

完整的示例代码，而不仅仅是对要调用的 API 的引用。
同时提供 C 和 C + + 实现。
适用于 Unicode 和 MBCS 项目设置。
将错误代码作为输入参数。这一点很重要，因为线程的最后一个错误代码只有在定义良好的点才有效。输入参数允许调用方遵循文档化的契约。
实现适当的异常安全。与所有其他隐式使用异常的解决方案不同，在构造返回值时引发异常时，此实现不会泄漏内存。
正确使用 FORMAT_MESSAGE_IGNORE_INSERTS标志。有关更多信息，请参见 FORMAT _ MESSAGE _ IGNORE _ INSERTS 标志的重要性。
正确的错误处理/错误报告与其他一些答案不同，它们默默地忽略错误。

这个答案是从 Stack Overflow 文档中整合的。下面的用户对示例做出了贡献: Stackptr、阿杰、 Cody Gray、我可以检查。

小开

我把这个留在这里，因为我以后需要用它。它是一个小型二进制兼容工具的源代码，在汇编、 C 和 C + + 中都能很好地工作。

GetErrorMessageLib.c (编译为 GetErrorMessageLib.dll)

#include <Windows.h>


/***
* returns 0 if there was enough space, size of buffer in bytes needed
* to fit the result, if there wasn't enough space. -1 on error.
*/
__declspec(dllexport)
int GetErrorMessageA(DWORD dwErrorCode, LPSTR lpResult, DWORD dwBytes)
{
LPSTR tmp;
DWORD result_len;


result_len = FormatMessageA (
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_ALLOCATE_BUFFER,
NULL,
dwErrorCode,
LANG_SYSTEM_DEFAULT,
(LPSTR)&tmp,
0,
NULL
);


if (result_len == 0) {
return -1;
}


// FormatMessage's return is 1 character too short.
++result_len;


strncpy(lpResult, tmp, dwBytes);


lpResult[dwBytes - 1] = 0;
LocalFree((HLOCAL)tmp);


if (result_len <= dwBytes) {
return 0;
} else {
return result_len;
}
}


/***
* returns 0 if there was enough space, size of buffer in bytes needed
* to fit the result, if there wasn't enough space. -1 on error.
*/
__declspec(dllexport)
int GetErrorMessageW(DWORD dwErrorCode, LPWSTR lpResult, DWORD dwBytes)
{
LPWSTR tmp;
DWORD nchars;
DWORD result_bytes;


nchars = dwBytes >> 1;


result_bytes = 2 * FormatMessageW (
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_ALLOCATE_BUFFER,
NULL,
dwErrorCode,
LANG_SYSTEM_DEFAULT,
(LPWSTR)&tmp,
0,
NULL
);


if (result_bytes == 0) {
return -1;
}


// FormatMessage's return is 1 character too short.
result_bytes += 2;


wcsncpy(lpResult, tmp, nchars);
lpResult[nchars - 1] = 0;
LocalFree((HLOCAL)tmp);


if (result_bytes <= dwBytes) {
return 0;
} else {
return result_bytes * 2;
}
}

内联版本(GetErrorMessage.h) :

#ifndef GetErrorMessage_H
#define GetErrorMessage_H
#include <Windows.h>


/***
* returns 0 if there was enough space, size of buffer in bytes needed
* to fit the result, if there wasn't enough space. -1 on error.
*/
static inline int GetErrorMessageA(DWORD dwErrorCode, LPSTR lpResult, DWORD dwBytes)
{
LPSTR tmp;
DWORD result_len;


result_len = FormatMessageA (
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_ALLOCATE_BUFFER,
NULL,
dwErrorCode,
LANG_SYSTEM_DEFAULT,
(LPSTR)&tmp,
0,
NULL
);


if (result_len == 0) {
return -1;
}


// FormatMessage's return is 1 character too short.
++result_len;


strncpy(lpResult, tmp, dwBytes);


lpResult[dwBytes - 1] = 0;
LocalFree((HLOCAL)tmp);


if (result_len <= dwBytes) {
return 0;
} else {
return result_len;
}
}


/***
* returns 0 if there was enough space, size of buffer in bytes needed
* to fit the result, if there wasn't enough space. -1 on error.
*/
static inline int GetErrorMessageW(DWORD dwErrorCode, LPWSTR lpResult, DWORD dwBytes)
{
LPWSTR tmp;
DWORD nchars;
DWORD result_bytes;


nchars = dwBytes >> 1;


result_bytes = 2 * FormatMessageW (
FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_ALLOCATE_BUFFER,
NULL,
dwErrorCode,
LANG_SYSTEM_DEFAULT,
(LPWSTR)&tmp,
0,
NULL
);


if (result_bytes == 0) {
return -1;
}


// FormatMessage's return is 1 character too short.
result_bytes += 2;


wcsncpy(lpResult, tmp, nchars);
lpResult[nchars - 1] = 0;
LocalFree((HLOCAL)tmp);


if (result_bytes <= dwBytes) {
return 0;
} else {
return result_bytes * 2;
}
}


#endif /* GetErrorMessage_H */

动态用例(假设错误代码有效，否则需要 -1检查) :

#include <Windows.h>
#include <Winbase.h>
#include <assert.h>
#include <stdio.h>


int main(int argc, char **argv)
{
int (*GetErrorMessageA)(DWORD, LPSTR, DWORD);
int (*GetErrorMessageW)(DWORD, LPWSTR, DWORD);
char result1[260];
wchar_t result2[260];


assert(LoadLibraryA("GetErrorMessageLib.dll"));


GetErrorMessageA = (int (*)(DWORD, LPSTR, DWORD))GetProcAddress (
GetModuleHandle("GetErrorMessageLib.dll"),
"GetErrorMessageA"
);
GetErrorMessageW = (int (*)(DWORD, LPWSTR, DWORD))GetProcAddress (
GetModuleHandle("GetErrorMessageLib.dll"),
"GetErrorMessageW"
);


GetErrorMessageA(33, result1, sizeof(result1));
GetErrorMessageW(33, result2, sizeof(result2));


puts(result1);
_putws(result2);


return 0;
}

常规用例(假设错误代码有效，否则需要 -1返回检查) :

#include <stdio.h>
#include "GetErrorMessage.h"
#include <stdio.h>


int main(int argc, char **argv)
{
char result1[260];
wchar_t result2[260];


GetErrorMessageA(33, result1, sizeof(result1));
puts(result1);


GetErrorMessageW(33, result2, sizeof(result2));
_putws(result2);


return 0;
}

例如，与汇编 gnu 一起使用，如 MinGW32中所示(同样，假设错误代码有效，否则需要 -1检查)。

    .global _WinMain@16


.section .text
_WinMain@16:
// eax = LoadLibraryA("GetErrorMessageLib.dll")
push $sz0
call _LoadLibraryA@4 // stdcall, no cleanup needed


// eax = GetProcAddress(eax, "GetErrorMessageW")
push $sz1
push %eax
call _GetProcAddress@8 // stdcall, no cleanup needed


// (*eax)(errorCode, szErrorMessage)
push $200
push $szErrorMessage
push errorCode
call *%eax // cdecl, cleanup needed
add $12, %esp


push $szErrorMessage
call __putws // cdecl, cleanup needed
add $4, %esp


ret $16


.section .rodata
sz0: .asciz "GetErrorMessageLib.dll"
sz1: .asciz "GetErrorMessageW"
errorCode: .long 33


.section .data
szErrorMessage: .space 200

结果: The process cannot access the file because another process has locked a portion of the file.

小开

由于 c + + 11，您可以使用标准库而不是 FormatMessage:

#include <system_error>


if (!SomeWin32Function()){
DWORD error = ::GetLastError();
std::string message = std::system_category().message(error);
...
}

小开

解决方案

下面是使用 std: : string/wstring 的最小 C + + 示例。

可以同时使用 Unicode 和 MBCS
兼容 MSVC 6.0-> VS2022和 GCC/MinGW (兼容-lstdc + +) ，很可能也兼容 Clang。
不需要 C + + 11
适用于 WindowsXP 及更高版本。

#include <windows.h>
#include <string>


typedef std::basic_string<TCHAR> String;


String errorMessage(DWORD dwError)
{
LPTSTR lpBuffer = NULL;
String ret = TEXT("");
if (FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER | FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS, NULL, dwError, 0, (LPTSTR)&lpBuffer, 0, NULL))
ret = String(lpBuffer);
LocalFree(lpBuffer);
return ret;
}

但是它没有任何错误检查，如果找不到指定的错误，它只返回一个空字符串。如果愿意，可以实现自己的错误检查。

为什么浪费时间写很多代码，当很少的代码做技巧？

附加信息 ^{(你可以跳过这一步)}

我为 dwLanguageId 传递了0，因为这是正确的方法，因为其他的答案没有注意到 MAKELANGID 宏是不推荐的，而 不应使用是不一致的，在某些语言中根本不起作用。

下面是 Windows SDK 10.0.19041.0(2020.05-12)中 winnt.h 的一段摘录，其中说明了这个问题:

//
// ** DEPRECATED ** DEPRECATED ** DEPRECATED ** DEPRECATED ** DEPRECATED **
//
//  DEPRECATED: The LCID/LANGID/SORTID concept is deprecated, please use
//  Locale Names instead, eg: "en-US" instead of an LCID like 0x0409.
//  See the documentation for GetLocaleInfoEx.
//
//  A language ID is a 16 bit value which is the combination of a
//  primary language ID and a secondary language ID.  The bits are
//  allocated as follows:
//
//       +-----------------------+-------------------------+
//       |     Sublanguage ID    |   Primary Language ID   |
//       +-----------------------+-------------------------+
//        15                   10 9                       0   bit
//
//  WARNING:  This pattern is broken and not followed for all languages.
//            Serbian, Bosnian & Croatian are a few examples.
//
//  WARNING:  There are > 6000 human languages.  The PRIMARYLANGID construct
//            cannot support all languages your application may encounter.
//            Please use Language Names, such as "en".
//
//  WARNING:  There are > 200 country-regions.  The SUBLANGID construct cannot
//            represent all valid dialects of languages such as English.
//            Please use Locale Names, such as "en-US".
//
//  WARNING:  Some languages may have more than one PRIMARYLANGID.  Please
//            use Locale Names, such as "en-FJ".
//
//  WARNING:  Some languages do not have assigned LANGIDs.  Please use
//            Locale Names, such as "tlh-Piqd".
//
//  It is recommended that applications test for locale names rather than
//  attempting to construct/deconstruct LANGID/PRIMARYLANGID/SUBLANGID
//
//  Language ID creation/extraction macros:
//
//    MAKELANGID    - construct language id from a primary language id and
//                    a sublanguage id.
//    PRIMARYLANGID - extract primary language id from a language id.
//    SUBLANGID     - extract sublanguage id from a language id.
//
//  Note that the LANG, SUBLANG construction is not always consistent.
//  The named locale APIs (eg GetLocaleInfoEx) are recommended.
//
//  DEPRECATED: Language IDs do not exist for all locales
//
// ** DEPRECATED ** DEPRECATED ** DEPRECATED ** DEPRECATED ** DEPRECATED **
//

看来这些信息还没有传到 MAKELANGID的官方 MSDN 文档中。

即使它工作正常，它也是最糟糕的选项，因为它试图在指定的 LangID 上查找错误字符串，而且只查找一个 ID，如果它不存在，就会失败。而使用0将很可能返回至少 什么的，即使该错误没有本地化为用户的语言。

引自 MSDN 格式信息:

[在] dwLanguageId

请求消息的语言标识符。如果 dwFlags 包含 FORAT _ MESSAGE _ FROM _ STRING，则忽略此参数。

如果在此参数中传递特定的 LANGID，FormatMessage 将仅返回该 LANGID 的消息。如果函数找不到该 LANGID 的消息，则将 Last-ERROR 设置为 ERROR _ RESOURCE _ LANG _ NOT _ FOUND。如果传入0，FormatMessage 将按以下顺序查找 LANGID 的消息:

语言中立

线程 LANGID，基于线程的区域设置值

用户默认 LANGID，基于用户的默认区域设置值

系统默认 LANGID，基于系统默认区域设置值

美式英语

如果 FormatMessage 没有找到前面任何 LANGID 的消息，它将返回存在的任何语言消息字符串。如果失败，它将返回 ERROR _ RESOURCE _ LANG _ NOT _ FOUND。

如何从 GetLastError ()返回的错误代码中获取错误消息？

解决方案

附加信息 (你可以跳过这一步)

附加信息 ^{(你可以跳过这一步)}