2014-11-24 16:19-0500, Steven Rostedt: > On Mon, 24 Nov 2014 22:00:01 +0100 > Radim Krčmář <rkrcmar@xxxxxxxxxx> wrote: > > > 2014-11-24 11:40+0100, Jan Kiszka: > > The format string has to be a string literal[1]; we could change it to > > allow expressions[2], but what we want is almost possible through a > > direct call to trace_seq_printf()[3]. > > > > The raw result would look like > > > > #define __print(fmt, args...) ({ \ > > const char *buf_start = trace_seq_buffer_ptr(p); \ > > trace_seq_printf(p, fmt, args); \ > > trace_seq_putc(p, '\0'); \ > > buf_start; \ > > }) > > > > TP_printk("%s%s", [...], > > __entry->has_error ? __print("(0x%x)", __entry->error_code) : "") > > > > and would be acceptable if something __print-like made it into a ftrace > > helper[4]. (Userspace won't be able to nicely print it otherwise.) > > You mean if we add something like a __print_conditional(cond, fmt, ...); The benefit of _conditional is cleaner code? (_conditional would be possible as a #define on top of generic print, the ternary seems to be parsed correctly.) > For this case you would have: > > TP_printk("%s%s", [...], > __print_conditional(__entry->has_error, " (0x%x)", __entry->error_code)); > > Where __print_conditional() will return "" when "cond" is false, and > will return the formatted string otherwise. (This might introduce 'const char empty[] = ""'.) > That wouldn't be too hard to implement. I'll look at the patch tommorrow. Thanks. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html