Re: [PATCH v2 3/4] build: Don't make object files for dtrace on macOS

[Roman Bolshakov <r.bolshakov@yadro.com>]

On Fri, Jul 17, 2020 at 12:35:16PM +0300, Roman Bolshakov wrote:
> dtrace on macOS uses unresolved symbols with a special prefix to define
> probes [1], only headers should be generated for USDT (dtrace(1)). But
> it doesn't support backwards compatible no-op -G flag [2] and implicit
> build rules fail.
> 
> 1. https://markmail.org/message/6grq2ygr5nwdwsnb
> 2. https://markmail.org/message/5xrxt2w5m42nojkz
> 
> Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
> Cc: Cameron Esfahani <dirty@apple.com>
> Signed-off-by: Roman Bolshakov <r.bolshakov@yadro.com>
> ---
>  Makefile.objs | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/Makefile.objs b/Makefile.objs
> index d22b3b45d7..982f15ba30 100644
> --- a/Makefile.objs
> +++ b/Makefile.objs
> @@ -211,5 +211,7 @@ trace-events-files = $(SRC_PATH)/trace-events $(trace-events-subdirs:%=$(SRC_PAT
>  trace-obj-y = trace-root.o
>  trace-obj-y += $(trace-events-subdirs:%=%/trace.o)
>  trace-obj-$(CONFIG_TRACE_UST) += trace-ust-all.o
> +ifneq ($(CONFIG_DARWIN),y)
>  trace-obj-$(CONFIG_TRACE_DTRACE) += trace-dtrace-root.o
>  trace-obj-$(CONFIG_TRACE_DTRACE) += $(trace-events-subdirs:%=%/trace-dtrace.o)
> +endif
> -- 
> 2.26.1
> 

An article about DTrace [1] mentions that FreeBSD also doesn't need that:
"On FreeBSD/Mac OS X, you do not have to generate a separate probe
object file for linking. This makes the compilation process much more
straightforward [...]"

I don't know for sure but perhaps "-G" makes dummy object files there.

1. https://www.ibm.com/developerworks/aix/library/au-dtraceprobes.html

Thanks,
Roman