Seg faults and slack pack parsing!

MylesCLin · 02-23-2005, 06:00 PM

Here's my code for 'parsing' slack pack info from a file in /var/log/packages/

Code:

void treesel(GtkWidget *item){
gchar *name, *buf[60], *pkginfo[200];
FILE *pkg;
GtkLabel *label;
label = GTK_LABEL (GTK_BIN (item)->child);
gtk_label_get (label, &name);
char *path[strlen(name) + strlen("/var/log/packages/")];
memcpy(path, "/var/log/packages/",strlen(name));
strcat(path, name);
pkg = fopen(path,"r");
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
printf("\nPackage name: %s\n", buf);
memcpy(pkginfo, buf,strlen(buf));
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
printf("\nCompressed file size: %s\n", buf);
strcat(pkginfo, buf);
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
printf("\nUncompressed package size: %s\n", buf);
strcat(pkginfo, buf);
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
fscanf(pkg,"%s",buf);
printf("\nPackage location: %s\n", buf);
strcat(pkginfo, buf);
fflush(pkg);
fclose(pkg);
printf("\n-----------\n%s",&pkginfo);
}

It works fine reading a pack that starts like:

Code:

PACKAGE NAME:     gtkradiant-1.5.0-2005-01-16.i386
COMPRESSED PACKAGE SIZE:     2240 K
UNCOMPRESSED PACKAGE SIZE:     6320 K
PACKAGE LOCATION: gtkradiant-1.5.0-2005-01-16.i386.tgz
PACKAGE DESCRIPTION:
FILE LIST:

But this one here:

Code:

PACKAGE NAME:     acct-6.3.2-i386-1
COMPRESSED PACKAGE SIZE:     52 K
UNCOMPRESSED PACKAGE SIZE:     130 K
PACKAGE LOCATION: /var/log/mount/slackware/ap/acct-6.3.2-i386-1.tgz
PACKAGE DESCRIPTION:
acct: acct (process accounting utilities)
acct:
acct: This is a set of utilities which reports and summarizes data about
acct: user connect times and process execution statistics.  To activate
acct: process accounting, create the log file (touch /var/log/pacct), and
acct: then use the accton command to start it (accton /var/log/pacct).
acct: Be aware that the log file can grow to be quite large.
acct:
acct: The GNU process accounting utilities were written by Noel Cragg.
acct:
acct:
FILE LIST:

...generates a segfault.

Any ideas?

Tinkster · 02-23-2005, 06:59 PM

Quote:

Code:

*buf[60]

Code:

echo "/var/log/packages/gtkradiant-1.5.0-2005-01-16.i386.tgz" | wc -c
55
echo "/var/log/packages/var/log/mount/slackware/ap/acct-6.3.2-i386-1.tgz" | wc -c
67

The problem is (I believe) that some of your packages already
have /var/log/packages in location, others don't. You prepend
it regardless.

Cheers,
Tink

MylesCLin · 02-23-2005, 08:33 PM

Thanks for the reply!

I don't believe I understand, I'm still new to C and I need a better explanation.
Can you help me to understand how to 'fix' this?

Tinkster · 02-23-2005, 08:43 PM

Try making your buffer e.g. 80 and see if it still
bombs out on you ...

What I was trying to say is that you're writing more
to buf than 60 characters ...

Code:

gchar *name, *buf[60], *pkginfo[200];
FILE *pkg;
GtkLabel *label;
label = GTK_LABEL (GTK_BIN (item)->child);
gtk_label_get (label, &name);
char *path[strlen(name) + strlen("/var/log/packages/")];
memcpy(path, "/var/log/packages/",strlen(name));
strcat(path, name);
pkg = fopen(path,"r");

For the gtkradiant package, for example, you have
PACKAGE LOCATION: gtkradiant-1.5.0-2005-01-16.i386.tgz
which is (prepended with /var/log/packages) 55 chars for path,
and fits into buf ...

For acc
PACKAGE LOCATION: /var/log/mount/slackware/ap/acct-6.3.2-i386-1.tgz
PLUS the /var/log/packages you add to path is 67 ... when you
write that to buf you write too much => segfault

Clear enough?

Cheers,
Tink

MylesCLin · 02-23-2005, 09:20 PM

I increased the size of the buffer and it still segfaults.

Also, path has nothing to do with the contents of the buffer, it's just the var I use to build the appropriate path.

Tinkster · 02-23-2005, 10:45 PM

Heh - sorry, I didn't look at the code TOO closely.

But the thing is the same:

Code:

echo "acct: process accounting, create the log file (touch /var/log/pacct), and" | wc -c
74

The lines of description don't fit, just check if ANYTHING
in the file is longer than your buffer.

Also, can you find out (using gdb) at which line it bombs out
on you? That would certainly help finding the fluke :)

Cheers,
Tink

MylesCLin · 02-23-2005, 11:20 PM

Figured it out, I screwed the path, not the buf.
it was:

Code:

memcpy(path, "/var/log/packages/",strlen(name));

Should have been:

Code:

memcpy(path, "/var/log/packages/",strlen(name) + strlen("/var/log/packages/"));

Danke for the help!