Thread: Problem with cin to char*

Hi, I wanted to pass an input to a char* then pass it to a class member.
but before i even get to the class member, i got stuck in the char* itself.

Code:

#include <iostream>
using namespace::std;

class CTest
{
public:
	char *name;
};

CTest Test;
char *gName = "";

int main()
{
	cout<<"Enter Name: ";
	cin>>gName;   //<--here's the error
	Test.name = gName;
	return 0;
}

after i compile, it's ok.
but once i run it.
then it breaks and popup a message saying:

Unhandled exception at 0x104f01be (msvcp80d.dll) in test.exe: 0xC0000005: Access violation writing location 0x0041664b.

then opens a page on the "istream" file.


any leads to solve this?
I thought char* was able to store as string?

>> char *gName = "";
That points gName to a constant string that happens to be empty. You cannot modify the constant string, which is why it fails when you try to.

You should use the C++ string class instead of character arrays. If you are forced to use C style strings, you need to allocate memory for the character array before using cin to read into it.

Originally Posted by twomers

>> Test.name = gName;

Should that be strcat or strcpy or something?



EDIT -

change

Code:

	cout<<"Enter Name: ";
	cin>>gName;   //<--here's the error

to

Code:

	char *gName;
	cout<<"Enter Name: ";
	cin>>gName;   //<--here's the error

and I would recommend the strings rather than char*'s

thanks mate, but it doesn't help.

Code:

#include <iostream>
using namespace::std;

class CTest
{
public:
	char *name;
};

CTest Test;
//char *gName = "";

int main()
{
	char *gName = "";
	cout<<"Enter Name: ";
	cin>>gName;
	//Test.name = gName;
	return 0;
}

Originally Posted by Daved

>> char *gName = "";
That points gName to a constant string that happens to be empty. You cannot modify the constant string, which is why it fails when you try to.

You should use the C++ string class instead of character arrays. If you are forced to use C style strings, you need to allocate memory for the character array before using cin to read into it.

gosh~!!!
<<snip profanity>>
man, i was trying to do everything in char*.
guess i have no choice.

Originally Posted by Salem

It means you have to either allocate some space, or use an array of chars.

You can't just declare a char* and assume it points at infinite amounts of memory you can do anything you like with.

Oh, and watch the language in future.

ah, Salem. sorry to brake the rules.
anyway, so i guess if i do every char* into char[99]; would be ok?
how much bytes or size does a string takes anyway?
coz if everything in char[99] works less than a string then i'll use char[99].

It is unlikely that you need to worry about how much memory your string takes up. If you do, then the amount used by the C++ string class depends on your platform and its implementation of the string class. Most likely it would use less memory than char[99] for a name.

Of course, you should use the string class because it is easier to use and safer than character arrays, not because it might use less memory in this particular instance.

Originally Posted by Daved

It is unlikely that you need to worry about how much memory your string takes up. If you do, then the amount used by the C++ string class depends on your platform and its implementation of the string class. Most likely it would use less memory than char[99] for a name.

Of course, you should use the string class because it is easier to use and safer than character arrays, not because it might use less memory in this particular instance.

ah~~~ ok.
Now I've got more reasons to change all my char* into string.
Thanks Daved.