C++ constructor help!!

[KENNY LIU]

class description (MyString):

class defines a sequence of characters (similar to class string). The implementation must be as an array of characters that are dynamically allocated and resized as necessary. You must use a null character to terminate the string - just like C-strings are null terminated.

deafult constructor:

/// get_length(char *s) gets length of s before null character. buf is private data member to store array for MyString
 
MyString::MyString(char *s)
{
buf = new char(get_length(s)+1); 
 
for(int i=0;s;++i)
buf[i] = s[i];
 
buf[get_length(s)+1] = '\0';
}
 

Copy constructor

MyString::MyString(const MyString &s)
{
char *s_arr = s.buf;
 
buf = new char(s.length()+1); ////length() gets length of MyString object before null
 
for(int i=0;s_arr;++i)
{
buf[i] = s.buf[i];
}
 
buf[length()+1] = '\0';
}
 

I'm getting seg faults and errors when I test these constructors. DO you see any errors in my code? I can't figure it out.

Thanks

[johny10151981]

yes, i see
on line 10, on the first code block,
on line 12, on second code block.

how???

a[4]="joh";
 
//now you are getting new str with  the same lenght
b[]=new char(a.length()+1);
//so, it has length 4. 
//according to your code
b[a.length()+1]='\0';
 
//what is that mean? simple;
//b[3+1], that is b[0],b[1],b[2],b[3],b[4].. whcih make the length 5, but you have only 4 byte lenght.. 
//that is all
 
 
 
 

[KENNY LIU]

I'm sorry, I'm not sure I understand your answer. So what am i doing wrong and how do i fix it

[johny10151981]

you should use this.

b[a.length()]='\0';
 

[KENNY LIU]

Like this???

MyString::MyString(char *s)
{
buf = new char(get_length(s)+1); 
 
for(int i=0;s;++i)
buf[i] = s[i];
 
buf[get_length(s)] = '\0';
}
 

[johny10151981]

yes, and there is more
your for condition is it limited at all??? it seems unlimited.

your for loop should be like this

for(int i=0;s[i];++i) or for(int i=0;s[i]!=0;++i)
or for(int i=0;s;++i,s++)
 

[morfanaion]

ok, maybe I can point you to this line:

buf = new char(get_length(s)+1);

Here you are calling the constructor of a char and assigning it the value of get_length(s) + 1. To allocate an array, you need to use [ and ].

buf = new char[get_length(s)+1];