Re: [libvirt] [PATCH] Allow stack traces to be included with log messages

On 05/09/2012 08:22 AM, Daniel P. Berrange wrote: > From: "Daniel P. Berrange" <berrange(a)redhat.com&gt; > > Sometimes it is useful to see the callpath for log messages. > This change enhances the log filter syntax so that stck traces s/stck/stack/ > can be show by setting '1:+NAME' instead of '1:NAME'. Cool. > * docs/logging.html.in: Document new syntax > * configure.ac: Check for execinfo.h > * src/util/logging.c, src/util/logging.h: Add support for > stack traces Of course, this seems to be Linux-only, but still useful.

> +++ b/docs/logging.html.in > @@ -114,8 +114,10 @@ > </h3> > <p>The syntax for filters and outputs is the same for both types of > variables.</p> > - <p>The format for a filter is:</p> > - <pre>x:name</pre> > + <p>The format for a filter is one of:</p> > + <pre> > + x:name (log message only) > + x:+name (log message + stack trace)</pre> Does x:+name error out on systems where tracing is not built in, or does it silently fall back to x:name?

> @@ -538,6 +546,7 @@ static int virLogFiltersCheck(const char *input) { > for (i = 0;i < virLogNbFilters;i++) { > if (strstr(input, virLogFilters[i].match)) { > ret = virLogFilters[i].priority; > + *flags = virLogFilters[i].flags; Is the double space intentional?

> + > +static void virLogStackTraceToFd(int fd) > +{ > +#ifdef HAVE_EXECINFO_H > + void *array[100]; > + int size; > + > +#define STRIP_DEPTH 3 > + > + size = backtrace(array, sizeof(array)/sizeof(array[0])); Write the second argument as ARRAY_CARDINALITY(array). > + backtrace_symbols_fd(array + STRIP_DEPTH, size - STRIP_DEPTH, fd); > + ignore_value(safewrite(fd, "\n", 1)); > +#else > + const char *msg = "stack trace not available on this platform"; > + ignore_value(safewrite(fd, msg, strlen(msg))); Is this a one-time error message, printed on first use, or will it appear on every log message?