* Re: Segmentation Fault on Stack Overflow
[not found] ` <20140105175831.4640d8a5@pws-pc.ntlworld.com>
@ 2014-01-05 21:33 ` Peter Stephenson
2014-01-05 22:12 ` Bart Schaefer
0 siblings, 1 reply; 2+ messages in thread
From: Peter Stephenson @ 2014-01-05 21:33 UTC (permalink / raw)
To: Zsh Hackers' List
On Sun, 5 Jan 2014 17:58:31 +0000
Peter Stephenson <p.w.stephenson@ntlworld.com> wrote:
> It might be possible to do a little better by querying some of the
> memory-related limits (I would guess available stack space is the key
> one, but some investigation will be necessary) to see if one of the
> limits is getting short and aborting function calls in a handlable
> fashion at that level. Unhelpfully, limits (from getrlimit()) and
> current usage (from getrusage()) don't seem to map cleanly onto one
> another, and this is all rather system-specific, so this doesn't look
> like a trivial project.
What's more, on Linux the resources useful here aren't actually reported by
getrusage() at the moment. The best I've found with a bit of poking
around locally (I might do better online, but I might as well ask here
first) is /proc/$$/status. This is obviously completely system specific
and quite possible specific to certain kernel versions. The code below
does seem to do roughly what I want (at the moment it reports the limits
and usage rather than checking the values) but I can't help thinking I'm
missing something. It's going to be hard to get something of general
use out of this sort of thing.
{
struct rlimit rlimit;
int found = 0;
long usage, limit;
char buffer[256];
FILE *sfile;
sprintf(buffer, "/proc/%d/status", getpid());
sfile = fopen(buffer, "r");
if (sfile) {
while (fgets(buffer, 256, sfile)) {
if (!strncmp(buffer, "VmStk:", 6) &&
getrlimit(RLIMIT_STACK, &rlimit) == 0) {
const char *ptr = buffer + 6;
while (!isdigit(*ptr))
ptr++;
usage = atol(ptr);
limit = rlimit.rlim_cur == (rlim_t)-1 ?
rlimit.rlim_max : rlimit.rlim_cur;
fprintf(stderr, "stack: limit = %ld, usage = %ld\n",
limit, usage * 1024);
found++;
} else if (!strncmp(buffer, "VmData:", 7) &&
getrlimit(RLIMIT_DATA, &rlimit) == 0) {
const char *ptr = buffer + 7;
while (!isdigit(*ptr))
ptr++;
usage = atol(ptr);
limit = rlimit.rlim_cur == (rlim_t)-1 ?
rlimit.rlim_max : rlimit.rlim_cur;
fprintf(stderr, "stack: limit = %ld, usage = %ld\n",
limit, usage * 1024);
found++;
}
if (found == 2)
break;
}
fflush(stderr);
fclose(sfile);
}
}
pws
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