[Qemu-devel] [PATCH] trace: ensure $(tracetool-y) is defined in top level makefile

[Qemu-devel] [PATCH] trace: ensure $(tracetool-y) is defined in top level makefile

[Daniel P. Berrange]

The build rules for trace files have a dependancy on $(tracetool-y).
This variable populated in the trace/Makefile.objs file and thus its
definition gets pulled into the top level makefile. This happens too
late in the process though, so by the time $(tracetool-y) is defined,
make has already evaluated $(tracetool-y) in the dependancies and
found it to be empty. The result is that when the tracetool source
is changed, the generated files are not rebuilt. The solution is to
define the variable in the top level makefile too

Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
---
 Makefile | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/Makefile b/Makefile
index 1c4c04f..dffc74b 100644
--- a/Makefile
+++ b/Makefile
@@ -85,6 +85,9 @@ GENERATED_SOURCES += $(TRACE_SOURCES)
 
 trace-group-name = $(shell dirname $1 | sed -e 's/[^a-zA-Z0-9]/_/g')
 
+tracetool-y = $(SRC_PATH)/scripts/tracetool.py
+tracetool-y += $(shell find $(SRC_PATH)/scripts/tracetool -name "*.py")
+
 %/trace.h: %/trace.h-timestamp
 	@cmp $< $@ >/dev/null 2>&1 || cp $< $@
 %/trace.h-timestamp: $(SRC_PATH)/%/trace-events $(tracetool-y)
-- 
2.9.3

Re: [Qemu-devel] [PATCH] trace: ensure $(tracetool-y) is defined in top level makefile

[Eric Blake]

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On 03/15/2017 05:56 AM, Daniel P. Berrange wrote:
> The build rules for trace files have a dependancy on $(tracetool-y).
> This variable populated in the trace/Makefile.objs file and thus its
> definition gets pulled into the top level makefile. This happens too
> late in the process though, so by the time $(tracetool-y) is defined,
> make has already evaluated $(tracetool-y) in the dependancies and
> found it to be empty. The result is that when the tracetool source
> is changed, the generated files are not rebuilt. The solution is to
> define the variable in the top level makefile too
> 
> Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> ---
>  Makefile | 3 +++
>  1 file changed, 3 insertions(+)

Does this mean the definitions in trace/Makefile.objs are now redundant
and can be omitted?

> 
> diff --git a/Makefile b/Makefile
> index 1c4c04f..dffc74b 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -85,6 +85,9 @@ GENERATED_SOURCES += $(TRACE_SOURCES)
>  
>  trace-group-name = $(shell dirname $1 | sed -e 's/[^a-zA-Z0-9]/_/g')
>  
> +tracetool-y = $(SRC_PATH)/scripts/tracetool.py
> +tracetool-y += $(shell find $(SRC_PATH)/scripts/tracetool -name "*.py")

Should this also include the comment currently in trace/Makefile.objs:

######################################################################
# tracetool source files
# Every rule that invokes tracetool must depend on this so code is
regenerated
# if tracetool itself changes.

But it certainly looks like you're on the right track for fixing the
issue I ran into.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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Re: [Qemu-devel] [PATCH] trace: ensure $(tracetool-y) is defined in top level makefile

[Daniel P. Berrange]

On Wed, Mar 15, 2017 at 06:44:25AM -0500, Eric Blake wrote:
> On 03/15/2017 05:56 AM, Daniel P. Berrange wrote:
> > The build rules for trace files have a dependancy on $(tracetool-y).
> > This variable populated in the trace/Makefile.objs file and thus its
> > definition gets pulled into the top level makefile. This happens too
> > late in the process though, so by the time $(tracetool-y) is defined,
> > make has already evaluated $(tracetool-y) in the dependancies and
> > found it to be empty. The result is that when the tracetool source
> > is changed, the generated files are not rebuilt. The solution is to
> > define the variable in the top level makefile too
> > 
> > Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> > ---
> >  Makefile | 3 +++
> >  1 file changed, 3 insertions(+)
> 
> Does this mean the definitions in trace/Makefile.objs are now redundant
> and can be omitted?

Hmm, I'm not sure, but quite possibly true.

> 
> > 
> > diff --git a/Makefile b/Makefile
> > index 1c4c04f..dffc74b 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -85,6 +85,9 @@ GENERATED_SOURCES += $(TRACE_SOURCES)
> >  
> >  trace-group-name = $(shell dirname $1 | sed -e 's/[^a-zA-Z0-9]/_/g')
> >  
> > +tracetool-y = $(SRC_PATH)/scripts/tracetool.py
> > +tracetool-y += $(shell find $(SRC_PATH)/scripts/tracetool -name "*.py")
> 
> Should this also include the comment currently in trace/Makefile.objs:
> 
> ######################################################################
> # tracetool source files
> # Every rule that invokes tracetool must depend on this so code is
> regenerated
> # if tracetool itself changes.
> 
> But it certainly looks like you're on the right track for fixing the
> issue I ran into.

IMHO such comments are pointless - they're just stating the obvious.

Regards,
Daniel
-- 
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