[lttng-dev] [RFC] [PATCH] -Werror=old-style-definition and UST tracepoints

[lttng-dev] [RFC] [PATCH] -Werror=old-style-definition and UST tracepoints

[Hollis Blanchard]

I've defined a tracepoint without arguments:

    TRACEPOINT_EVENT(

         qemu_tb_hash,

         flushall,

         TP_ARGS(void),

         TP_FIELDS()

    )


When I build (with -Werror=old-style-definition), I get this error:

    In file included from /home/hollisb/work/qemu.git/exec.c:59:0:

    /home/hollisb/work/qemu.git/tracepoints.h:24:2: error: function declaration isn?t a prototype [-Werror=strict-prototypes]

    /home/hollisb/work/qemu.git/tracepoints.h: In function ?__tracepoint_cb_qemu_tb_hash___flushall?:

    /home/hollisb/work/qemu.git/tracepoints.h:24:2: error: old-style function definition [-Werror=old-style-definition]

    cc1: all warnings being treated as errors


The preprocessed code looks like so:

    extern struct

    # 129 "/usr/local/include/lttng/tracepoint.h" 3

                   tracepoint

    # 24 "/home/hollisb/work/qemu.git/tracepoints.h"

      __tracepoint_qemu_tb_hash___flushall

    # 19 "/home/hollisb/work/qemu.git/tracepoints.h"

      ; static __attribute__ (( always_inline )) __inline__ void

      __tracepoint_cb_qemu_tb_hash___flushall

    # 19 "/home/hollisb/work/qemu.git/tracepoints.h"

      () { struct tracepoint_probe *__tp_probe; if (!tracepoint_dlopen.rcu_read_lock_sym_bp) return; tracepoint_dlopen.rcu_read_lock_sym_bp(); __tp_probe = ({ typeof(__tracepoint_qemu_tb_hash___flushall.probes) _________p1 = ((typeof(__tracepoint_qemu_tb_hash___flushall.probes)) (tracepoint_dlopen.rcu_dereference_sym_bp(((void *) (__tracepoint_qemu_tb_hash___flushall.probes))))); (_________p1); }); if (__builtin_expect(!!(!__tp_probe), 0)) goto end; do { void *__tp_cb = __tp_probe->func; void *__tp_data = __tp_probe->data; ((void (*)(void *__tp_data)) (__tp_cb)) (__tp_data); } while ((++__tp_probe)->func); end: tracepoint_dlopen.rcu_read_unlock_sym_bp(); } static __attribute__ (( always_inline )) __inline__ void


I believe the problem comes from -Werror=old-style-definition not liking 
that empty "()", i.e. tracepoint_cb_qemu_tb_hash___flushall() { ... }. 
The following patch seems to work for me; is there a reason it isn't 
already written this way?

diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h

index 4b773bb..60d8c73 100644

--- a/include/lttng/tracepoint.h

+++ b/include/lttng/tracepoint.h

@@ -88,7 +88,7 @@ extern "C" {

  #define _TP_EXDATA_VAR20(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t)      __tp_data,b,d,f,h,j,l,n,p,r,t

  

  /* _TP_EXPROTO* extract tuples of type, var */

-#define _TP_EXPROTO0()

+#define _TP_EXPROTO0()                                         void

  #define _TP_EXPROTO2(a,b)                                      a b

  #define _TP_EXPROTO4(a,b,c,d)                                  a b,c d

  #define _TP_EXPROTO6(a,b,c,d,e,f)                              a b,c d,e f


If this is OK, I'm happy to resend as a proper patch.

-- 
Hollis Blanchard
Mentor Graphics, Embedded Systems Division

[lttng-dev] [RFC] [PATCH] -Werror=old-style-definition and UST tracepoints

[Mathieu Desnoyers]

* Hollis Blanchard (hollis_blanchard at mentor.com) wrote:
[...]
> I believe the problem comes from -Werror=old-style-definition not liking  
> that empty "()", i.e. tracepoint_cb_qemu_tb_hash___flushall() { ... }.  
> The following patch seems to work for me; is there a reason it isn't  
> already written this way?

Good catch !

Fixed as master commit:

commit 86637aa6452f66dee5f769461668c2ea059b3a30
Author: Mathieu Desnoyers <mathieu.desnoyers at efficios.com>
Date:   Mon Jun 11 09:53:07 2012 -0400

    Fix: tracepoint.h should not generate old-style definitions

and merged into stable-2.0.

Thanks!

Mathieu


>
> diff --git a/include/lttng/tracepoint.h b/include/lttng/tracepoint.h
>
> index 4b773bb..60d8c73 100644
>
> --- a/include/lttng/tracepoint.h
>
> +++ b/include/lttng/tracepoint.h
>
> @@ -88,7 +88,7 @@ extern "C" {
>
>  #define _TP_EXDATA_VAR20(a,b,c,d,e,f,g,h,i,j,k,l,m,n,o,p,q,r,s,t)      __tp_data,b,d,f,h,j,l,n,p,r,t
>
>  
>
>  /* _TP_EXPROTO* extract tuples of type, var */
>
> -#define _TP_EXPROTO0()
>
> +#define _TP_EXPROTO0()                                         void
>
>  #define _TP_EXPROTO2(a,b)                                      a b
>
>  #define _TP_EXPROTO4(a,b,c,d)                                  a b,c d
>
>  #define _TP_EXPROTO6(a,b,c,d,e,f)                              a b,c d,e f
>
>
> If this is OK, I'm happy to resend as a proper patch.
>
> -- 
> Hollis Blanchard
> Mentor Graphics, Embedded Systems Division
>
>
> _______________________________________________
> lttng-dev mailing list
> lttng-dev at lists.lttng.org
> http://lists.lttng.org/cgi-bin/mailman/listinfo/lttng-dev

-- 
Mathieu Desnoyers
Operating System Efficiency R&D Consultant
EfficiOS Inc.
http://www.efficios.com