func TestLogBacktraceAt(t *testing.T) {
setFlags()
defer logging.swap(logging.newBuffers())
// The peculiar style of this code simplifies line counting and maintenance of the
// tracing block below.
var infoLine string
setTraceLocation := func(file string, line int, delta int) {
_, file = filepath.Split(file)
infoLine = fmt.Sprintf("%s:%d", file, line+delta)
err := logging.traceLocation.Set(infoLine)
if err != nil {
t.Fatal("error setting log_backtrace_at: ", err)
}
}
{
// Start of tracing block. These lines know about each other's relative position.
file, line := util.Caller(0)
setTraceLocation(file, line, +2) // Two lines between Caller and Info calls.
Info("we want a stack trace here")
if err := logging.traceLocation.Set(""); err != nil {
t.Fatal(err)
}
}
numAppearances := strings.Count(contents(InfoLog), infoLine)
if numAppearances < 2 {
// Need 2 appearances, one in the log header and one in the trace:
// log_test.go:281: I0511 16:36:06.952398 02238 log_test.go:280] we want a stack trace here
// ...
// github.com/clog/glog_test.go:280 (0x41ba91)
// ...
// We could be more precise but that would require knowing the details
// of the traceback format, which may not be dependable.
t.Fatal("got no trace back; log is ", contents(InfoLog))
}
}
func (l *loggingT) Caller(depth int) (file string, line int) {
return util.Caller(depth + 1)
}