c++ - How do I fix this error with allocation and deallocation mismatch?

Question

Cppcheck report as an error "Mismatching allocation and deallocation: cname" for the line with delete cname;. I don't see what the problem with using my version of code is - it looks working.

Is my code wrong? How do I fix it? And what are the consequences of using my code?

if ( lenght != 0 )
{
   char *cname = new char[lenght+1];    
   inbin.read(reinterpret_cast<char *>( cname ), lenght );
   cname[lenght] = '\0';
   *ptr_string = cname;             
   delete cname;
 }      

Answer 1

是的，当您使用语法分配数组时new …[…]，您应该使用delete[]. 在您的情况下，您需要delete[] cname;.

如果你使用错误的形式delete来匹配你的分配new，你有未定义的行为：

§5.3.5/2 [expr.delete]在第一种选择（删除对象）中，操作数的值可以是空指针值、指向由先前的新表达式delete创建的非数组对象的指针，或指向表示此类对象的基类的子对象的指针。如果不是，则行为未定义。在第二种选择（删除数组）中，操作数的值可以是空指针值或由前一个数组new-expression产生的指针值。如果不是，则行为未定义。delete

Answer 2

if ( lenght != 0 )
    {
        char *cname = new char[lenght+1];   
        inbin.read(reinterpret_cast<char *>( cname ), lenght );
        cname[lenght] = '\0';
        *ptr_string = cname;                
        delete[] cname;
    }