* Stefan Hajnoczi (stefa...@gmail.com) wrote: > 2011/9/20 Mathieu Desnoyers <comp...@krystal.dyndns.org>: > > * Lluís Vilanova (vilan...@ac.upc.edu) wrote: > >> Stefan Hajnoczi writes: > >> > >> > On Fri, Sep 16, 2011 at 06:59:38PM +0200, Lluís Vilanova wrote: > >> >> Signed-off-by: Lluís Vilanova <vilan...@ac.upc.edu> > >> >> --- > >> >> trace-events | 4 ++-- > >> >> 1 files changed, 2 insertions(+), 2 deletions(-) > >> >> > >> >> diff --git a/trace-events b/trace-events > >> >> index 9d1fbbb..b653d70 100644 > >> >> --- a/trace-events > >> >> +++ b/trace-events > >> >> @@ -418,8 +418,8 @@ milkymist_pfpu_pulse_irq(void) "Pulse IRQ" > >> >> # hw/milkymist-softusb.c > >> >> milkymist_softusb_memory_read(uint32_t addr, uint32_t value) "addr %08x > >> >> value %08x" > >> >> milkymist_softusb_memory_write(uint32_t addr, uint32_t value) "addr > >> >> %08x value %08x" > >> >> -milkymist_softusb_mevt(uint8_t m) "m %d" > >> >> -milkymist_softusb_kevt(uint8_t m) "m %d" > >> >> +milkymist_softusb_mevt(uint8_t _m) "m %d" > >> >> +milkymist_softusb_kevt(uint8_t _m) "m %d" > >> > >> > The LTTng community has been very responsive in addressing namespace > >> > issues with libust. Let's post more details and see if it can be fixed > >> > in libust. > >> > >> > Could you please post your gcc and libust versions? > >> > >> > I have not been able to reproduce the problem on Debian libust-dev > >> > 0.15-3. My gcc version is Debian gcc 4.6.1-4. > >> > >> Yup, I was using libust-dev 0.5 (debian stable). After switching to 0.15 > >> (debian > >> testing) other problems arise. > >> > >> For example, in my box compiling osdep.c yields lots of "variable > >> ‘__tp_cb_data’ > >> set but not used", but using a minimal example does not raise such > >> problems, so > >> I'm assuming this is related to some namespace problems related to some > >> other > >> code in qemu's headers. > > > > If you can find a few minutes to provide: > > > > 1) a link to the git repository/commit ID you are testing > > 2) the exact configuration you use (detailed way to reproduce the > > problem, as a sequence of commands from a pristine repository) > > > > It will allow me to look into this warning and fix it. > > AFAICT the only problem with libust is the __tp_cb_data set but not > used warning that gcc 4.6 emits, see my test program: > > #include <stdint.h> > #include <ust/tracepoint.h> > > DECLARE_TRACE(ust_milkymist_softusb_mevt, TP_PROTO(uint8_t m), > TP_ARGS(m)); > > int main(int argc, char **argv) > { > return 0; > } > > You will get an error with gcc 4.6 and libust 0.15: > > $ gcc -o a -Wall a.c
Ah, I see. This is due to the backward compatibility API I added in 0.15 for qemu. It skips using the __tp_cb_data private data. So it does make sense that the compiler complains about this. I can add a __attribute__((unused)), as proposed by Lluís. > > QEMU itself does have one problem with libust 0.15. We do > DECLARE_TRACE(name, TP_PROTO(void), TP_ARGS()). This results in a > compiler error but we can fix this my changing our tracepoints to use > DECLARE_TRACE(name, TP_PROTO(), TP_ARGS()) I think. Perhaps libust's > behavior here has changed, it shouldn't be hard to update QEMU's > tracetool tracepoint generator though. For tracepoints without arguments, you need to use something like: TRACEPOINT_EVENT_NOARGS(name, TP_FIELDS()) (note: the full support of TP_FIELDS() declaration will come in UST 2.0. For UST 0.15, it's just ignored) The _NOARGS variant lets you handle the (void) 0 parameter case. Thanks, Mathieu > > If you adapt the example program I used above to use TP_PROTO(void), > TP_ARGS() then you get this error: > > a.c: In function ‘__trace_ust_milkymist_softusb_mevt’: > a.c:4:1: error: expected declaration specifiers or ‘...’ before ‘)’ token > a.c:4:1: error: expected ‘)’ before ‘__tp_it_func’ > a.c:4:1: error: expected expression before ‘)’ token > a.c:4:1: warning: variable ‘__tp_it_func’ set but not used > [-Wunused-but-set-variable] > a.c: At top level: > a.c:4:1: error: expected declaration specifiers or ‘...’ before ‘)’ token > a.c:4:1: error: expected ‘;’, ‘,’ or ‘)’ before ‘void’ > a.c:4:1: error: expected declaration specifiers or ‘...’ before ‘)’ token > a.c:4:1: error: expected ‘;’, ‘,’ or ‘)’ before ‘void’ > a.c: In function ‘trace_ust_milkymist_softusb_mevt’: > a.c:4:1: warning: variable ‘__tp_cb_data’ set but not used > [-Wunused-but-set-variable] > > I can't say for sure whether I ever tested old libust versions with > void tracepoints. Perhaps we simply never had any and the tracetool > generator has always been broken. Or perhaps libust changed its > behavior. > > Stefan > -- Mathieu Desnoyers Operating System Efficiency R&D Consultant EfficiOS Inc. http://www.efficios.com