blocks|key|1459868|text|FormatMessage会将GetLastError(http://msdn.microsoft.com/en-us/library/ms679360(VS.85%2529.aspx)'s+integer+return+)转换为文本消息。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|1459869|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/ms679351(VS.85).aspx|1|http://msdn.microsoft.com/en-us/library/ms679360(VS.85%2529.aspx)'s^0|0|D|0|S|1T|1|0^^$0|@$1|2|3|4|5|6|7|N|8|@]|9|@$A|O|B|P|1|Q]|$A|R|B|S|1|T]]|C|$]]|$1|D|3|-4|5|6|7|U|8|@]|9|@]|C|$]]]|E|$F|$5|G|H|I|C|$J|K]]|L|$5|G|H|I|C|$J|M]]]]

<a href="http://msdn.microsoft.com/en-us/library/ms679351(VS.85).aspx" rel="noreferrer">FormatMessage</a> will turn <a href="http://msdn.microsoft.com/en-us/library/ms679360(VS.85).aspx" rel="noreferrer">GetLastError</a>'s integer return into a text message.

blocks|key|1245191|text|MSDN提供了一些示例代码来演示如何同时使用FormatMessage()和GetLastError()：Retrieving+the+Last-Error+Code|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1245192|entityMap|0|LINK|mutability|MUTABLE|url|http://msdn.microsoft.com/en-us/library/ms680582%2528VS.85%2529.aspx^0|M|F|12|E|1H|U|0|0^^$0|@$1|2|3|4|5|6|7|N|8|@$9|O|A|P|B|C]|$9|Q|A|R|B|C]]|D|@$9|S|A|T|1|U]]|E|$]]|$1|F|3|-4|5|6|7|V|8|@]|D|@]|E|$]]]|G|$H|$5|I|J|K|E|$L|M]]]]

MSDN has some sample code that demonstrates how to use <code>FormatMessage()</code> and <code>GetLastError()</code> together: <a href="http://msdn.microsoft.com/en-us/library/ms680582%28VS.85%29.aspx" rel="noreferrer">Retrieving the Last-Error Code</a>

blocks|key|1245206|text|//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+%7C+FORMAT_MESSAGE_FROM_SYSTEM+%7C+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;
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1245207|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>//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)&amp;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;
}
</code></pre>

blocks|key|1245251|text|如果你使用的是c#，你可以使用下面的代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1245252|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+%7C+FormatMessageFlags.FORMAT_MESSAGE_FROM_SYSTEM+%7C+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+"+%2B+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+->+"+%2B+e.ToString();
++++++++}
++++}
}|code-block|syntax|javascript|1245253|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

If you're using c# you can use this code:

<pre><code>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

 /// &lt;summary&gt;
 /// Gets a user friendly string message for a system error code
 /// &lt;/summary&gt;
 /// &lt;param name="errorCode"&gt;System error code&lt;/param&gt;
 /// &lt;returns&gt;Error string&lt;/returns&gt;
 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 -&gt; " + e.ToString();
 }
 }
}
</code></pre>

blocks|key|1245266|text|void+WinErrorCodeToString(DWORD+ErrorCode,+string&+Message)
{
char*+locbuffer+=+NULL;
DWORD+count+=+FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM+%7C+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+%2B+count))+==+'\r')+%7C%7C
++++++++++++(c+==+'\n'))+{
++++++++++++count--;
++++++++++++back%2B%2B;
++++++++}

++++++++if+(back)+{
++++++++++++locbuffer[count%2B%2B]+=+'\n';
++++++++++++locbuffer[count]+=+'\0';
++++++++}

++++++++Message+=+"Error:+";
++++++++Message+%2B=+locbuffer;
++++}
++++LocalFree(locbuffer);
}
else
{
++++Message+=+"Unknown+error+code:+"+%2B+to_string(ErrorCode);
}
}|type|code-block|depth|inlineStyleRanges|entityRanges|data|syntax|javascript|1245267|unstyled|entityMap^0|0^^$0|@$1|2|3|4|5|6|7|G|8|@]|9|@]|A|$B|C]]|$1|D|3|-4|5|E|7|H|8|@]|9|@]|A|$]]]|F|$]]

<pre><code>void WinErrorCodeToString(DWORD ErrorCode, string&amp; Message)
{
char* locbuffer = NULL;
DWORD count = FormatMessageA(FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ALLOCATE_BUFFER, NULL, ErrorCode,
 0, (LPSTR)&amp;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);
}
}
</code></pre>

blocks|key|1460054|text|如果你需要支持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。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1460055|CString+FormatErrorMessage(DWORD+ErrorCode)
{
++++TCHAR+++*pMsgBuf+=+NULL;
++++DWORD+++nMsgLen+=+FormatMessage(FORMAT_MESSAGE_ALLOCATE_BUFFER+%7C
++++++++FORMAT_MESSAGE_FROM_SYSTEM+%7C+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;
}|code-block|syntax|javascript|1460056|此外，为了简洁起见，我发现以下方法很有用：|1460057|CString+GetLastErrorString()
{
++++return+FormatErrorMessage(GetLastError());
}|1460058|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

If you need to support MBCS as well as Unicode, Mr.C64's answer is not quite enough. The buffer must be declared TCHAR, and cast to LPTSTR. Note that this code doesn't deal with the annoying newline that Microsoft appends to the error message.

<pre><code>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&lt;LPTSTR&gt;(&amp;pMsgBuf), 0, NULL);
 if (!nMsgLen)
 return _T("FormatMessage fail");
 CString sMsg(pMsgBuf, nMsgLen);
 LocalFree(pMsgBuf);
 return sMsg;
}
</code></pre>

Also, for brevity I find the following method useful:

<pre><code>CString GetLastErrorString()
{
 return FormatErrorMessage(GetLastError());
}
</code></pre>

blocks|key|1245392|text|我会把它留在这里，因为我稍后会用到它。它是一个小的二进制兼容工具的源代码，它在汇编、C和C%2B%2B中都可以很好地工作。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|1245393|C(编译为GetErrorMessageLib.dll)|1245394|#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+%7C+FORMAT_MESSAGE_IGNORE_INSERTS+%7C+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.
++++%2B%2Bresult_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+%7C+FORMAT_MESSAGE_IGNORE_INSERTS+%7C+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+%2B=+2;

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

++++if+(result_bytes+<=+dwBytes)+{
++++++++return+0;
++++}+else+{
++++++++return+result_bytes+*+2;
++++}
}|code-block|syntax|javascript|1245395|内联版本(GetErrorMessage.h)：|1245396|#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+%7C+FORMAT_MESSAGE_IGNORE_INSERTS+%7C+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.
++++%2B%2Bresult_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+%7C+FORMAT_MESSAGE_IGNORE_INSERTS+%7C+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+%2B=+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+*/|1245397|动态用法(假设错误码有效，否则需要检查)：|1245398|#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;
}|1245399|常规使用情况(假设错误代码有效，否则需要返回检查)：|1245400|#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;
}|1245401|在MinGW32中使用汇编gnu的示例(同样，假设错误代码有效，否则需要检查)。|1245402|++++.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+%25eax
++++call+_GetProcAddress@8+//+stdcall,+no+cleanup+needed

++++//+(*eax)(errorCode,+szErrorMessage)
++++push+$200
++++push+$szErrorMessage
++++push+errorCode+++++++
++++call+*%25eax+//+cdecl,+cleanup+needed
++++add+$12,+%25esp

++++push+$szErrorMessage
++++call+__putws+//+cdecl,+cleanup+needed
++++add+$4,+%25esp

++++ret+$16

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

++++.section+.data
szErrorMessage:+.space+200|1245403|结果：The+process+cannot+access+the+file+because+another+process+has+locked+a+portion+of+the+file.|offset|length|style|CODE|1245404|entityMap^0|0|0|0|0|0|0|0|0|0|0|0|3|2K|0^^$0|@$1|2|3|4|5|6|7|16|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|17|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|18|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|19|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|1A|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|1B|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|1C|8|@]|9|@]|A|$G|H]]|$1|Q|3|R|5|6|7|1D|8|@]|9|@]|A|$]]|$1|S|3|T|5|F|7|1E|8|@]|9|@]|A|$G|H]]|$1|U|3|V|5|6|7|1F|8|@]|9|@]|A|$]]|$1|W|3|X|5|F|7|1G|8|@]|9|@]|A|$G|H]]|$1|Y|3|Z|5|6|7|1H|8|@$10|1I|11|1J|12|13]]|9|@]|A|$]]|$1|14|3|-4|5|6|7|1K|8|@]|9|@]|A|$]]]|15|$]]

i'll leave this here since i will need to use it later. It's a source for a small binary compatible tool that will work equally well in assembly, C and C++.

GetErrorMessageLib.c (compiled to GetErrorMessageLib.dll)

<pre><code>#include &lt;Windows.h&gt;

/***
 * 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)&amp;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 &lt;= 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 &gt;&gt; 1;

 result_bytes = 2 * FormatMessageW (
 FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_ALLOCATE_BUFFER,
 NULL,
 dwErrorCode,
 LANG_SYSTEM_DEFAULT,
 (LPWSTR)&amp;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 &lt;= dwBytes) {
 return 0;
 } else {
 return result_bytes * 2;
 }
}
</code></pre>

inline version(GetErrorMessage.h):

<pre><code>#ifndef GetErrorMessage_H 
#define GetErrorMessage_H 
#include &lt;Windows.h&gt; 

/***
 * 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)&amp;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 &lt;= 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 &gt;&gt; 1;

 result_bytes = 2 * FormatMessageW (
 FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_IGNORE_INSERTS | FORMAT_MESSAGE_ALLOCATE_BUFFER,
 NULL,
 dwErrorCode,
 LANG_SYSTEM_DEFAULT,
 (LPWSTR)&amp;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 &lt;= dwBytes) {
 return 0;
 } else {
 return result_bytes * 2;
 }
}

#endif /* GetErrorMessage_H */
</code></pre>

dynamic usecase(assumed that error code is valid, otherwise a -1 check is needed):

<pre><code>#include &lt;Windows.h&gt;
#include &lt;Winbase.h&gt;
#include &lt;assert.h&gt;
#include &lt;stdio.h&gt;

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;
}
</code></pre>

regular use case(assumes error code is valid, otherwise -1 return check is needed):

<pre><code>#include &lt;stdio.h&gt;
#include "GetErrorMessage.h"
#include &lt;stdio.h&gt;

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;
}
</code></pre>

example using with assembly gnu as in MinGW32(again, assumed that error code is valid, otherwise -1 check is needed).

<pre><code> .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
</code></pre>

result: <code>The process cannot access the file because another process has locked a portion of the file.</code>

blocks|key|1245440|text|由于使用了c%2B%2B11，您可以使用标准库而不是FormatMessage|type|unstyled|depth|inlineStyleRanges|offset|length|style|CODE|entityRanges|data|1245441|#include+<system_error>

std::string+GetLastErrorAsString(){
++++DWORD+errorMessageID+=+::GetLastError();
++++if+(errorMessageID+==+0)+{
++++++++return+std::string();+//No+error+message+has+been+recorded
++++}+else+{
++++++++return+std::system_category().message(errorMessageID);
++++}
}|code-block|syntax|javascript|1245442|entityMap^0|M|D|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@$9|N|A|O|B|C]]|D|@]|E|$]]|$1|F|3|G|5|H|7|P|8|@]|D|@]|E|$I|J]]|$1|K|3|-4|5|6|7|Q|8|@]|D|@]|E|$]]]|L|$]]

Since c++11, you can use the standard library instead of <code>FormatMessage</code>:

<pre class="lang-cpp prettyprint-override"><code>#include &lt;system_error&gt;

std::string GetLastErrorAsString(){
 DWORD errorMessageID = ::GetLastError();
 if (errorMessageID == 0) {
 return std::string(); //No error message has been recorded
 } else {
 return std::system_category().message(errorMessageID);
 }
}
</code></pre>

After a Windows API call, how can I get the last error message in a textual form?

<code>GetLastError()</code> returns an integer value, not a text message.

How to get the error message from the error code returned by GetLastError()?

Windows

在Windows API调用之后，如何以文本形式获取最后一个错误消息？GetLastError()返回整数值，而不是文本消息。

问如何从GetLastError()返回的错误码中获取错误信息？
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