Visual C ++：无效的分配大小。 为什么会这样呢？

Question

我在学习C ++的过程中。 我在VC ++上调试某些代码时遇到了以下错误，

Debug Error
*path to filename.exe*
Invalid allocation size:429496723 bytes.

该错误恰好在调试器到达以下块时发生： 编辑 ：我已经添加了整个主要功能来帮助检查maxlen是否采用任何意外值（尽管我没有注意到）

int main(){

    vector <Student_info> students;

    Student_info record;

    string::size_type maxlen=0;// length of the longest name

    //read and store all the students data.

    //maxlen contains the length of the name of the longest student.

    while (read(cin,record)){
    // find the length of the longest name
        max(maxlen,record.name.size());
        //add the student record to the vector.

        students.push_back(record);
    }
    //arrange the records alphabetically.
    sort(students.begin(),students.end(),compare);// this may look weird but the fact that the names have to be compared is checked using the predicate.

        //write out the names and grades.


        for(vector<Student_info>::size_type i =0;i!=students.size();i++){

            //padding to ensure that there is vertical alignment.
            cout<<students[i].name<<string(maxlen+1-students[i].name.size(),' ');// debugger stops here!
            //compute grade.
            try{
                double final_grade=grade(students[i]);
                streamsize prec=cout.precision();
                cout<<setprecision(3)<<final_grade<<setprecision(prec);
            }
            catch(domain_error e){
            //catch error if hw vector is empty!

                e.what();

            }
            cout<<endl;

            }
        return 0;
        }

Answer 1

您可能会看到这一行：

max(maxlen,record.name.size());

您是否可能表示：

maxlen = max(maxlen,record.name.size());

Answer 2

在将其初始化为0之后，您再也不会为maxlen分配一个值。然后，您从该值中减去1得到负的偏移量。

在您的第一个while循环中，您可能想要...

   maxlen = max( maxlen, record.name.size() );