linux-kernel - Re: [RFC 0/4] tools lib traceevent: Install fixes

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Date:	Tue, 2 Aug 2016 11:31:34 +0200
From:	Jiri Olsa <jolsa@...hat.com>
To:	Namhyung Kim <namhyung@...nel.org>
Cc:	Jiri Olsa <jolsa@...nel.org>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	lkml <linux-kernel@...r.kernel.org>,
	David Ahern <dsahern@...il.com>,
	Ingo Molnar <mingo@...nel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	"Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
Subject: Re: [RFC 0/4] tools lib traceevent: Install fixes

On Tue, Aug 02, 2016 at 12:10:55PM +0900, Namhyung Kim wrote:
> On Mon, Aug 01, 2016 at 07:41:28PM +0200, Jiri Olsa wrote:
> > hi,
> > sending traceevent changes to make this lib installable
> > under rpm spec.
> > 
> > Basically adding support to:
> >   - install header files
> >   - install version links
> > 
> > Having this patchset applied over the fedora source,
> > I could built following rpms:
> > 
> >   kernel-tools-libs
> >   kernel-tools-libs-devel
> > 
> > with added libtraceevent stuff:
> > 
> >   $ rpm -ql kernel-tools-libs
> >   /usr/lib64/libcpupower.so.0
> >   /usr/lib64/libcpupower.so.0.0.0
> >   /usr/lib64/libtraceevent.so.1
> >   /usr/lib64/libtraceevent.so.1.1.0
> > 
> >   $ rpm -ql kernel-tools-libs-devel
> >   /usr/include/cpufreq.h
> >   /usr/include/traceevent
> >   /usr/include/traceevent/event-parse.h
> >   /usr/include/traceevent/event-utils.h
> >   /usr/include/traceevent/kbuffer.h
> >   /usr/lib64/libcpupower.so
> >   /usr/lib64/libtraceevent.a
> >   /usr/lib64/libtraceevent.so
> > 
> > and could build following ex.c outside the kernel tree:
> > 
> >   $ cat ex.c 
> >   #include <traceevent/event-parse.h>
> > 
> >   int main(void)
> >   {
> >           struct pevent *pevent = pevent_alloc();
> >           printf("krava %p\n", pevent);
> >           return 0;
> >   }
> >   $ gcc -o ex ex.c -ltraceevent -ldl
> >   $ ./ex
> >   krava 0x10c6010
> >   $
> 
> On my system, building ex.c with libtraceevent failed:
> 
> $ gcc -I ~/.local/include/ ex.c -L ~/.local/lib64 -ltraceevent -ldl
> /home/namhyung/.local/lib64/libtraceevent.so: undefined reference to `str_error_r'
> collect2: error: ld returned 1 exit status
> 
> 
> Also I think it'd be better for libtraceevent has dependency to libdl
> explicitly so that we can get rid of -ldl at the end.

agreed, I'll queue your patch if v2 is needed

thanks,
jirka

> 
> 
> From ac7dc027274cb31f5860c4cf6219ea7584611e17 Mon Sep 17 00:00:00 2001
> From: Namhyung Kim <namhyung@...nel.org>
> Date: Tue, 2 Aug 2016 12:03:00 +0900
> Subject: [PATCH] tools lib traceevent: Add dependency to libdl
> 
> The libtraceevent has dependency to libdl due to plugins.  So if
> external program wants to link libtraceevent it also needs to add -ldl
> to the compiler command line.  Make it explicit so that external
> programs doesn't care about the internel dependency of libtraceevent
> anymore.
> 
> Signed-off-by: Namhyung Kim <namhyung@...nel.org>
> ---
>  tools/lib/traceevent/Makefile | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/tools/lib/traceevent/Makefile b/tools/lib/traceevent/Makefile
> index c76012ebdb9c..bae0c090c638 100644
> --- a/tools/lib/traceevent/Makefile
> +++ b/tools/lib/traceevent/Makefile
> @@ -173,7 +173,7 @@ $(TE_IN): force
>  	$(Q)$(MAKE) $(build)=libtraceevent
>  
>  $(OUTPUT)libtraceevent.so.$(EVENT_PARSE_VERSION): $(TE_IN)
> -	$(QUIET_LINK)$(CC) --shared $^ -Wl,-soname,libtraceevent.so.$(EP_VERSION) -o $@
> +	$(QUIET_LINK)$(CC) --shared $^ -Wl,-soname,libtraceevent.so.$(EP_VERSION) -o $@ -ldl
>  	@ln -sf $(@F) $(OUTPUT)libtraceevent.so
>  	@ln -sf $(@F) $(OUTPUT)libtraceevent.so.$(EP_VERSION)
>  
> -- 
> 2.9.2
>