Assertion failure in std::ispunct in a simple program

Question

I'm using the book C++primer by Stanley B.Lippman and this error is caused by the solution of Excersise 3.2.3 test 3.10.It requires that write a program that reads a string of characters including punctuation and writes what was read but with the punctuation removed.

here's the code:

#include "stdafx.h"
#include <iostream>
#include <string>
#include <cctype>

using namespace std;

int main() {
  string s;
  cout << "Please input a string of characters including punctuation:" << endl;
  getline(cin, s);
  for (auto c : s) {
     if (!ispunct(c))
         cout << c;
  }
  cout << endl;

 return 0;
}

when I run this code in Visual studio 2017 it shows this:

Debug Assertion failed.
Expression:c>=-1&&c<=255
For information on how your program can cause an assertion failure,see the Visual C++ documentation on asserts.

why it shows like this? I can't understand.

What is the line its asserting on? (add a comment to show us), Also, what is your input? — xEric_xD, Jan 19 '18 at 09:18
@manni66 good point - more clarification why - here: http://en.cppreference.com/w/cpp/string/byte/ispunct — PiotrNycz, Jan 19 '18 at 09:31
@ vahancho Oh!Thank you.I input a punctuation at the form of Chinese.Is it cause the error?But what is the mean of "c>=-1&&c<=255"? — Chen, Jan 19 '18 at 09:32
@ manni66 I tried but i think the problem is not here.This program only can be inputed ASCII code.If the form of input is fault it will cause error message. — Chen, Jan 19 '18 at 09:52
I input a"！",i think it is the reason why the Error appears. — Chen, Jan 19 '18 at 09:53

YSC · Accepted Answer · 2018-02-01T10:50:42.967

Although the assertion failure you get is due to a bad call to std::ispunct() (you should iterate over the string with an unsigned char), the proper solution would be to use std::iswpunct:

#include <iostream>
#include <string>
#include <locale>
#include <cwctype> // std::iswpunct

int main()
{
    std::wstring s;
    do {
        std::wcout << "Please input a string of characters including punctuation:\n";
    } while (!std::getline(std::wcin, s));

    for (auto c : s) {
        if (!std::iswpunct(c))
            std::wcout << c;
    }
    std::wcout << std::endl;
}

On a Windows platform, the conjunction of std::wstring¹ and std::iswpunct will let you handle Chinese characters right. Note that I assumed your system locale is "zh_CH.UTF-8". If it is not, you'll need to imbue your streams.

¹⁾ see this excellent answer about the difference between string and wstring.

Thank you for your useful answer.I ran this code and there is a small mistake is that 'iswpunct' not std space member.I deleted it and the code can be normal operated.Thank you. — Chen, Feb 01 '18 at 07:58

Assertion failure in std::ispunct in a simple program

1 Answers1