c++ - 编译器错误 MB_LEN_MAX 的假定值错误

Question

我目前正在尝试运行 this image segmentation program ，但是当我尝试编译它时遇到错误。要编译，您只需make，它运行命令

g++ -g -O3 -I. -o segment segment.cpp -lm

但是，它遇到了一个编译错误——它的输出是

In file included from /usr/include/wchar.h:887:0,
                 from /usr/include/c++/6/cwchar:44,
                 from /usr/include/c++/6/bits/postypes.h:40,
                 from /usr/include/c++/6/iosfwd:40,
                 from /usr/include/c++/6/ios:38,
                 from /usr/include/c++/6/istream:38,
                 from /usr/include/c++/6/fstream:38,
                 from ./pnmfile.h:27,
                 from segment.cpp:23:
/usr/include/x86_64-linux-gnu/bits/wchar2.h:448:3: error: #error "Assumed value of MB_LEN_MAX wrong"
 # error "Assumed value of MB_LEN_MAX wrong"
   ^~~~~
Makefile:14: recipe for target 'segment' failed
make: *** [segment] Error 1

这里是/usr/include/x86_64-linux-gnu/bits/wchar2.h的相关区域

  /* We would have to include <limits.h> to get a definition of MB_LEN_MAX.
     But this would only disturb the namespace.  So we define our own
     version here.  */
#define __WCHAR_MB_LEN_MAX  16
#if defined MB_LEN_MAX && MB_LEN_MAX != __WCHAR_MB_LEN_MAX
# error "Assumed value of MB_LEN_MAX wrong"
#endif
  if (__bos (__s) != (size_t) -1 && __WCHAR_MB_LEN_MAX > __bos (__s))
    return __wcrtomb_chk (__s, __wchar, __ps, __bos (__s));
  return __wcrtomb_alias (__s, __wchar, __ps);
}

以及segment.cpp的相关区域:

#include <cstdio>
#include <cstdlib>
#include <image.h>
#include <misc.h>
#include <pnmfile.h> //<-- Line 23 of segment.cpp, where the error occurs
#include "segment-image.h"

和pnmfile.h:

#include <cstdlib>
#include <climits>
#include <cstring>
#include <fstream> //<-- Line 27 of pnmfile.h where the error occurs
#include "image.h"
#include "misc.h"

有谁知道导致此错误的原因(如果是，如何解决)？我正在使用 g++ 6.4.0 运行 Ubuntu 16.04。感谢您提供的任何帮助!

编辑:我已经确认 fstream 确实有效。我编译如下

#include <iostream>
#include <cstdlib>
#include <fstream>

using namespace std;

int main() {
    ifstream is("in.txt");
    int a, b;
    is >> a >> b;
    cout << a << endl;
    cout << b << endl;
    return 0;
}

同样的命令

g++ -g -O3 -I. -o temp.exe temp.cpp -lm

它成功地打印出了从文本文件中读取的两个整数。

Answer 1

您需要包含 limits.h 来自您的 bits/wchar2.h 所在的同一个 libc。如果您查看 latter file 中的评论在您收到的 #error 上方，您会明白为什么 - 它可以防止混合不兼容的头文件。