Hi,

hi teckkies, a very cool and head ditching problem of char pointer
OS:ubuntu
language : c++

Running steps:
g++ file.cpp

./a.out
enter name
naveen(i entered my name)
segmentation fault


1)why this segmentation fault here?
2)can i use memset for char* as follows?

where str is declared as char* str;

and tell me which one is better?
memset(str, 0, sizeof(str));
memset(str, 0, 12);

if we declare str as char* str, Is that necessary to do memset?


please make me clear in this memset and char*

You never defined a storage location for your string. You defined a place to put the address of that storage location, but you never defined the location itself.

You defined a BUFF but never used it. You need to malloc some memory. str=malloc(BUF); should do it.

you tried to store your string in nothing
instead of char *str use char str[14]

allocate memory

My best guess at what you're trying to accomplish with that would be correctly done by
char *str = new char[BUFF+1];

Because str was an uninitialized pointer.

The first is wrong because sizeof(str) will always be the size of the pointer, not the size of the buffer pointed to.
The second would be right if str pointed to a big enough buffer.

That depends on the method used to allocate the buffer and I don't recall whether new char[] gives you a buffer that is reliably zero filled when allocated.

In C++ it is generally better to consistently use new, rather than use malloc in places like this where a corresponding C program would have used malloc.

It is also better to use std::string for text input, rather than matching the crude C approach of hard coding a guess at the required buffer size. So all the discussion here about how to use char* correctly is just because that is what the OP seems to have asked. It should not leave the impression that using char* is a good approach. Again I'm still just guessing at what the OP really wants to do, but I'm pretty sure it would be better done with std::string rather than with char*.

i use cin>> and cout<< all the time with char * with borland turbo C++ and g++
i see no reason to make it more complex to do C operations from withen C++

That probably means you were competent in C before you learned C++ (or maybe you had a really bad instructor for C++ that didn't know how to let go of C). I was competent in C long before C++ was invented, so I understand the viewpoint even if I don't agree with it.

Beginners in C usually make mistakes with char* exactly like the OP in this thread made. Any language feature responsible for such a high number of beginner mistakes is a hint that something should be taught differently.

At some point, a C++ programmer (like a C programmer), needs to develop a good understanding of pointers. But I think it is better for a beginner to build up to that understanding though examples where the meaning and value of using a pointer is more obvious.

I think text is something a beginner should be able to work with even before they develop that good understanding of pointers.

Using char* when the conceptual object you are thinking about is a text string, not a character pointer, is a flaw in C and an unnecessary distraction in C++.

The object the programmer want to input is a text string, not a character pointer. Then I expect the object he wants to manipulate is a text string, not a character pointer. A C programmer must learn how to use char* when he intends string. A C++ programmer doesn't need to.

or char str[BUFF];

That is a valid alternative for the trivial situation of the original example. I realized later that I may have been confusing matters when I ignored that post and said:

In fact, when str isn't a pointer, sizeof(str) isn't "always" the size of a pointer. So one of the advantages of declaring str the way smeezekitty suggested is that sizeof(str) will have the meaning a beginner expects.

i think i made myself unclear
i mean i use char * after i allocate it such as
[code]
char *p = new char[10];
cout<<"Enter your name:";
cin>>p;
cout<<"Hello " <<p;
delete p;
[/cpde]