On Sat, 19 Feb 2022 01:05:04 +0900
Fujii Masao <[email protected]> wrote:
>
>
> On 2022/02/18 19:59, Peter Eisentraut wrote:
> > On 18.02.22 09:24, Fujii Masao wrote:
> >> Or even backtrace should be logged by write_stderr() so that it's written
> >> to eventlog if necessary? I just wonder why backtrace_symbols_fd() is used
> >> only in ExceptionalCondition().
> >
> > Probably because it was simpler. It would also make sense to convert the
> > whole thing to use write_stderr() consistently.
> +1
> Attached is the updated version of the patch that uses write_stderr() to log
> the backtrace in assertion failure case.
>
> + if (nframes >= lengthof(buf))
> + appendStringInfo(&errtrace, "\n(backtrace limited to
> %zu frames)",
> + lengthof(buf));
>
> I found this doesn't work on FreeBSD, at least FreeBSD 13 that cfbot uses on
> Cirrus CI. When the backtrace is larger than 100, on FreeBSD, backtrace()
> seems to write the *99* (not 100) most recent function calls to the buffer.
> That is, the variable "nframes" is 99 while lengthof(buf) indicates 100. So
> the above message about backtrace limit will never be logged on FreeBSD.
> OTOH, on Linux and MacOS, backtrace() writes the 100 most recent function
> calls. I'm not sure if such a behavior on FreeBSD is expected or a bug.
>
> To issue the message whatever OS is, probably we need to modify
> set_backtrace() as follows, for example. But is this overkill? Thought?
>
>
> - void *buf[100];
> +#define BACKTRACE_MAX_FRAMES 100
> + void *buf[BACKTRACE_MAX_FRAMES + 1];
> int nframes;
> char **strfrms;
>
> nframes = backtrace(buf, lengthof(buf));
> + if (nframes > BACKTRACE_MAX_FRAMES)
> + nframes = BACKTRACE_MAX_FRAMES;
> strfrms = backtrace_symbols(buf, nframes);
> if (strfrms == NULL)
> return;
>
> for (int i = num_skip; i < nframes; i++)
> appendStringInfo(&errtrace, "\n%s", strfrms[i]);
> + if (nframes >= BACKTRACE_MAX_FRAMES)
> + appendStringInfo(&errtrace, "\n(backtrace limited to %d
> frames)",
> + BACKTRACE_MAX_FRAMES);
I think it would be better that users can get the same results in
different OS as as possible.
I have another comment. When the backtrace is output from elog,
two rows are skipped by num_skip and only 98 frames will appear
even though it is said "backtrace limited to 100 frames". So, how
about reporting the limiting number subtracted by num_skip, like this:
if (nframes >= lengthof(buf))
appendStringInfo(&errtrace, "\n(backtrace limited to %zu
frames)",
lengthof(buf) - num_skip);
or
if (nframes >= BACKTRACE_MAX_FRAMES)
appendStringInfo(&errtrace, "\n(backtrace limited to %d
frames)",
BACKTRACE_MAX_FRAMES -
num_skip);
Regards,
Yugo Nagata
--
Yugo NAGATA <[email protected]>
