string char * and char []

**Micko** · 01-10-2004

I'm coding a simple program that uses strings. I have two choices
to define string like char string[1024] taht is to assume max size of string then ask user to enter his own string from keyboard and then gets(string);
But what if I use char *string; and then gets(string);
Is this method dangerous and is there a chance if user enter a long string to overwrite some memory and cause program to crash? I experimented with this in Turbo C and everything seems to work fine. But....?
If someone can answer this I would appreciated
Thanks

**Codeplug** · 01-10-2004

Read this: Why gets() is bad / Buffer Overflows
And this: Get a line of text from the user/keyboard

Post if you have any questions.

gg

**Salem** · 01-10-2004

> experimented with this in Turbo C and everything seems to work fine. But....?
Yeah, that's DOS for you.

Your pointers can be left uninitialised pointing at who knows where in memory, and for a short while it's pretty much guaranteed that it will appear to work.

But as time passes, your program gets bigger and you trash more and more memory, sooner or later you'll come unstuck big-time.

Get a better OS and a better compiler, one which will kill your program at the first errant memory access.

**WaltP** · 01-10-2004

Originally posted by Salem
> experimented with this in Turbo C and everything seems to work fine. But....?
Yeah, that's DOS for you.

There's no mention of DOS. Turbo C 1.0 works just fine up into in XP....

**Salem** · 01-10-2004

It's still a DOS program working in an unprotected address space of 1MB
Running under XP doesn't change that

**Micko** · 01-11-2004

I have win 98 and access turbo C under command prompt, so
simple and clear: using char * is not recommended???

**Salem** · 01-11-2004

Sure you can use a char*
But you've got to remember to allocate some memory before you use it

char buff[BUFSIZ];
fgets( buff, BUFSIZ, stdin ); // check return

char *buff = malloc( BUFSIZ ); // check return
fgets( buff, BUFSIZ, stdin ); // check return

What you can never do (with any pointer) is simply use it without allocating any memory, like so
char *buff;
fgets( buff, BUFSIZ, stdin ); // BAD, very BAD

**rfbu** · 01-13-2004

hi,

my understanding is that if you are going to use char *pt, make sure you initialise pt to something

e.g.
char *pt;
char array[10];

pt = array;

or... pt = malloc(...);

I have forgotten how to use malloc

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