我正在尝试使用 msvc 2019 编译器编译一个项目，我知道之前已经编译过该项目。事实上，我实际上正在更新它的构建系统。我在标准模板库的源代码中遇到了一个奇怪的问题。基本上该项目包括
<cctype>_STD_BEGIN
using _CSTD isalnum;
using _CSTD isalpha;
using _CSTD iscntrl;
using _CSTD isdigit;
using _CSTD isgraph;
using _CSTD islower;
using _CSTD isprint;
using _CSTD ispunct;
using _CSTD isspace;
using _CSTD isupper;
using _CSTD isxdigit;
using _CSTD tolower;
using _CSTD toupper;
using _CSTD isblank;
_STD_END
但是当我编译我的项目时，这些声明都出现以下错误。
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(38): error C2039: 'isalnum': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(38): error C2873: 'isalnum': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(39): error C2039: 'isalpha': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(39): error C2873: 'isalpha': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(40): error C2039: 'iscntrl': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(40): error C2873: 'iscntrl': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(41): error C2039: 'isdigit': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(41): error C2873: 'isdigit': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(42): error C2039: 'isgraph': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(42): error C2873: 'isgraph': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(43): error C2039: 'islower': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(43): error C2873: 'islower': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(44): error C2039: 'isprint': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(44): error C2873: 'isprint': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(45): error C2039: 'ispunct': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(45): error C2873: 'ispunct': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(46): error C2039: 'isspace': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(46): error C2873: 'isspace': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(47): error C2039: 'isupper': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(47): error C2873: 'isupper': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(48): error C2039: 'isxdigit': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(48): error C2873: 'isxdigit': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(49): error C2039: 'tolower': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(49): error C2873: 'tolower': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(50): error C2039: 'toupper': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(50): error C2873: 'toupper': symbol cannot be used in a using-declaration
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(52): error C2039: 'isblank': is not a member of '`global namespace''
C:\Program Files (x86)\Microsoft Visual Studio\2019\Community\VC\Tools\MSVC\14.27.29110\include\cctype(52): error C2873: 'isblank': symbol cannot be used in a using-declaration
c++11 和 c++14 的结果是相同的。我试图制作一个最小的工作示例，但不能，因为我的玩具项目包含并使用
<cctype>我知道这将是一个艰难的过程，但是有人对这里可能发生的事情有任何想法吗？
我在 macOS 平台上也遇到了同样的错误；我的解决方案是
#include <_ctype.h>我也有同样的问题。该问题似乎是因为在多个标头中重新定义了符号。我什至没有包含这些标头中的任何方法，仍然出现错误， cstring、cstdio 和 cstdlib 中的 C2039 和 C2873
当我一开始添加这个时它就被修复了， #定义NO_REDEF_POSIX_FUNCS
我尝试了很多东西，在stackoverflow中看到了多种解决方案。所以想添加为我解决的问题。 希望这对某人有帮助。