'Segmentation fault' in example program

'Segmentation fault' in example program

[Frithjof]

Hey, 
when trying to compile the example from chapter "2.3.3 Linking
Guile into Programms" in the Reference Manual with gcc 3.3.5 I get the
following:

 gcc -o simple-guile simple-guile.c -lguile -pthread \
 -Wl,-rpath,/usr/local/lib

(gdb) run
Starting program: /home/frithjof/krams/guile/simple-guile 
[Thread debugging using libthread_db enabled]
[New Thread 1076640096 (LWP 3660)]
[New Thread 1087372208 (LWP 3663)]
guile> (* 3 3)
9
guile> (version)
"1.8.0"
guile> (my-hostname)

Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 1076640096 (LWP 3660)]
0x40180363 in strlen () from /lib/tls/libc.so.6
(gdb) 

Is my system just not set up correctly or is this a bug in Guile or one in
the example?

Yours,
Frithjof 


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Re: 'Segmentation fault' in example program

[Neil Jerram]

Frithjof <frithjof@minet.uni-jena.de> writes:

> Hey, 
> when trying to compile the example from chapter "2.3.3 Linking
> Guile into Programms" in the Reference Manual with gcc 3.3.5 I get the
> following:
>
>  gcc -o simple-guile simple-guile.c -lguile -pthread \
>  -Wl,-rpath,/usr/local/lib
>
> (gdb) run
> Starting program: /home/frithjof/krams/guile/simple-guile 
> [Thread debugging using libthread_db enabled]
> [New Thread 1076640096 (LWP 3660)]
> [New Thread 1087372208 (LWP 3663)]
> guile> (* 3 3)
> 9
> guile> (version)
> "1.8.0"
> guile> (my-hostname)
>
> Program received signal SIGSEGV, Segmentation fault.
> [Switching to Thread 1076640096 (LWP 3660)]
> 0x40180363 in strlen () from /lib/tls/libc.so.6
> (gdb) 
>
> Is my system just not set up correctly or is this a bug in Guile or one in
> the example?

Perhaps the HOSTNAME environment variable is not defined in the shell
where you tried this, and so getenv("HOSTNAME") is NULL?

You might like to try making the code for my-hostname safer, like
this:

static SCM
my_hostname (void)
{
  char *val = getenv ("HOSTNAME");
  return (val ? scm_str2string (val) : SCM_BOOL_F);
}

Regards,
        Neil



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Re: 'Segmentation fault' in example program

[Marius Vollmer]

Neil Jerram <neil@ossau.uklinux.net> writes:

> You might like to try making the code for my-hostname safer, like
> this:

We should make the example safe as well...

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Re: 'Segmentation fault' in example program

[Kevin Ryde]

Frithjof <frithjof@minet.uni-jena.de> writes:
>
> Is my system just not set up correctly or is this a bug in Guile or one in
> the example?

A bug in the example.  If you don't have a HOSTNAME variable then
getenv returns NULL, and scm_str2string can't cope with NULL.  I'll
change the manual.  Thanks.


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