Re: tlug: gcc question

["Scott M. Stone" <sstone@example.com>]

On Wed, 12 Jan 2000, Drew C. Poulin wrote:

> Pardon me if this question is inappropriate for this list, but after
> following it for several months, I thought someone might have a ready
> answer.
> 
> I'd like to continue to use gcc and xxgdb for some C classes I've
> been taking, but I seem to have encountered a difference in how gcc
> handles * char compared with how the MSVC++ compiler handles it.  An
> example is the code fragment below. gcc gives me a segmentation error when
> it runs, while MSVC++ doesn't.   Apparently the problem occurs when gets()
> tries to access *lname at 0x0.  I suppose there must be  a good reason for
> this.  Can anyone tell me what it is and tell me how I should be handling
> it?
> 
> Thank you for any insight.

ack!  they let you hand in code like this in your school??

1.  your pointers are uninitialized.  should be:
	char *fname=NULL;
	char *lname=NULL;

2.  you're doing a gets() call into an unknown region of memory - doing
the above should produce a segfault on any compiler, though, since it's
known to be null -- unless you've initialized them as null, you have no
idea where those things are pointing.

3.  You need to allocate memory for the pointers:
	fname=(char *)malloc(80);
	lname=(char *)malloc(80);
	memset(fname,0,80);
	memset(lname,0,80);

4.  You're using gets() at all.  egcs will bitch about it and tell you not
to use it, actually.  what you really want in this case would be:
	fgets(fname,80,stdin);


anyway, people (Chris) correct me if I'm wrong, but I think that the above
is correct...

> 
> Drew Poulin
> 
> 
> #include<stdio.h>
> 
> 
> main(){
>   
>   char *fname, *lname;
>  
>   puts("Enter fname:\n");
>   gets(fname);
>   puts("Enter lname:\n");
>   gets(lname);
>  printf("First name: %s\tLast name: %s\n", fname, lname);
> 
> }
> 
> 
> -------------------------------------------------------------------
> Next Technical Meeting: January 14 (Fri) 19:00
> * Topic: "glibc - current status and future developments"
> * Guest Speaker: Ulrich Drepper (Cygnus Solutions)
> * Place: Oracle Japan HQ 12F Seminar Room (New Otani Garden Court)
> -------------------------------------------------------------------
> more info: http://www.tlug.gr.jp        Sponsor: Global Online Japan
> 

--------------------------
Scott M. Stone, CCNA <sstone@example.com>
UNIX Systems and Network Engineer
Taos - The SysAdmin Company 

-------------------------------------------------------------------
Next Technical Meeting: January 14 (Fri) 19:00
* Topic: "glibc - current status and future developments"
* Guest Speaker: Ulrich Drepper (Cygnus Solutions)
* Place: Oracle Japan HQ 12F Seminar Room (New Otani Garden Court)
-------------------------------------------------------------------
more info: http://www.tlug.gr.jp        Sponsor: Global Online Japan