VC 编译 重复定义错误解决

MS VC6 链接错误处理
在Windows XP下编译的软件，放到Windows 2000上使用时，跳出了"无法找到动态链接库MSVCRTD.dll"的提示，后来还是直接将MSVCRTD.dll从WinXP系统目录下copy过来使用来解决问题的。

不过在解决问题过程中，有其他意外收获，现在记下来，说不定以后可参考一二。

刚开始时，我将MFC DLL改为静态库链接，编译，出现如下结果：

MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _realloc already defined in libcmt.lib(realloc.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _free already defined in libcmt.lib(free.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _malloc already defined in libcmt.lib(malloc.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _strchr already defined in libcmt.lib(strchr.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _sprintf already defined in libcmt.lib(sprintf.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _tolower already defined in libcmt.lib(tolower.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _getenv already defined in libcmt.lib(getenv.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _toupper already defined in libcmt.lib(toupper.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: __isctype already defined in libcmt.lib(isctype.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _atoi already defined in libcmt.lib(atox.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _strstr already defined in libcmt.lib(strstr.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _calloc already defined in libcmt.lib(calloc.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _strncpy already defined in libcmt.lib(strncpy.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _strncmp already defined in libcmt.lib(strncmp.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _memmove already defined in libcmt.lib(memmove.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _strtoul already defined in libcmt.lib(strtol.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _strtol already defined in libcmt.lib(strtol.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _fclose already defined in libcmt.lib(fclose.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _ungetc already defined in libcmt.lib(ungetc.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: __errno already defined in libcmt.lib(dosmap.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _sscanf already defined in libcmt.lib(sscanf.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _setlocale already defined in libcmt.lib(setlocal.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _printf already defined in libcmt.lib(printf.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _localtime already defined in libcmt.lib(localtim.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _time already defined in libcmt.lib(time.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: _fflush already defined in libcmt.lib(fflush.obj)
MSVCRTD.lib(MSVCRTD.dll) : error LNK2005: __strdup already defined in libcmt.lib(strdup.obj)

LINK : warning LNK4098: defaultlib "MSVCRTD" conflicts with use of other libs; use /NODEFAULTLIB:library

..\..\Output\Release/FirewallMan.exe : fatal error LNK1169: one or more multiply defined symbols found

Error executing link.exe.

相信一个善良的人对上面的错误不会熟视无睹的，我的解决方法当然是对症下药：

Link->Category: Input->Ignore libraries:libcmt

clean后重新编译，还有下面的链接错误：

Linking...

nafxcw.lib(appcore.obj) : error LNK2001: unresolved external symbol ___argv
nafxcw.lib(appcore.obj) : error LNK2001: unresolved external symbol ___argc
nafxcw.lib(apphelp.obj) : error LNK2001: unresolved external symbol __mbctype
nafxcw.lib(filelist.obj) : error LNK2001: unresolved external symbol __mbctype
nafxcw.lib(dcprev.obj) : error LNK2001: unresolved external symbol __mbctype
nafxcw.lib(timecore.obj) : error LNK2001: unresolved external symbol __mbctype

..\..\Output\Release/FirewallMan.exe : fatal error LNK1120: 3 unresolved externals

Error executing link.exe.

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后来尝试了很多方法，经过摸索，最后得出解决方法：

在Preprocessor中定义_AFXDLL

如果它提示：fatal error C1189: #error : Please use the /MD switch for _AFXDLL builds

就这样改：

C/C++->Code Generation->Multithread DLL （即实现/MD选项）