Re: Makefile.lib: cmd_dtc: warning: missing whitespace after the macro name

[Antony Pavlov <antonynpavlov@gmail.com>]

On Mon, 12 Sep 2022 10:01:52 +0200
Sascha Hauer <s.hauer@pengutronix.de> wrote:

Hi Sascha!

> On Wed, Sep 07, 2022 at 11:21:18AM +0300, Antony Pavlov wrote:
> > Hi Everyone!
> > 
> > During MIPS ath79_defconfig build I have a 'missing whitespace after the macro name' warning:
> > 
> >   AS [P]  arch/mips/dts/ar9331_tl_mr3020.dtb.pbl.o
> >   DTC     arch/mips/dts/ar9344-tl-wdr4300-v1.7.dtb
> > <stdin>:1:9: warning: missing whitespace after the macro name
> >   XZKERN  arch/mips/dts/ar9344-tl-wdr4300-v1.7.dtb.z
> > 
> > E.g. see https://gitlab.com/frantony/barebox/-/jobs/2969826747#L47
> > 
> > The reason is the scripts/Makefile.lib generates a C macro with the point symbol in the macro name because the arch/mips/dts/ar9344-tl-wdr4300-v1.7.dts file name contains the point symbol before '.dts', as a result we have:
> > 
> >   #define ar9344_tl_wdr4300_v1.7_dts 1
> > 
> > e.g.
> > 
> >   barebox$ grep -RHn -o "define ar9344_tl_wdr4300_v1.* 1" . 2>/dev/null
> >   ./arch/mips/dts/.ar9344-tl-wdr4300-v1.7.dtb.cmd:1:define ar9344_tl_wdr4300_v1.7_dts 1
> > 
> > cmd_dtc in scripts/Makefile.lib substitutes the '-' symbols with the '_' symbols but do nothing with other unwanted C preprocessor macro name symbols.
> > 
> > It looks like the linux kernel has no problems with extra point symbols in dts file names, there are several files with extra dot in dts:
> > 
> >   barebox$ find dts/ -iname '*.*.dts' | wc -l
> >   33
> > 
> > So we have to fix Makefile.lib.
> > 
> > This simple patch fixes the warning problem:
> > 
> > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> > index 16308497b84..2f79656c1e9 100644
> > --- a/scripts/Makefile.lib
> > +++ b/scripts/Makefile.lib
> > @@ -363,7 +363,7 @@ $(obj)/%.dtb.z: $(obj)/%.dtb FORCE
> >  dts-frags = $(subst $(quote),,$(CONFIG_EXTERNAL_DTS_FRAGMENTS))
> >  quiet_cmd_dtc = DTC     $@
> >  # For compatibility between make 4.2 and 4.3
> > -cmd_dtc = /usr/bin/env echo -e '$(pound)define $(subst -,_,$(*F))_dts 1\n'$(foreach f,$< $(dts-frags),'$(pound)include "$(f)"\n') | \
> > +cmd_dtc = /usr/bin/env echo -e '$(pound)define $(subst -,_,$(subst .,_,$(*F)))_dts 1\n'$(foreach f,$< $(dts-frags),'$(pound)include "$(f)"\n') | \
> >  	$(CPP) $(dtc_cpp_flags) -x assembler-with-cpp -o $(dtc-tmp) - ; \
> >  	$(objtree)/scripts/dtc/dtc -O dtb -o $@ -b 0 \
> >  		-i $(srctree)/arch/$(SRCARCH)/dts $(DTC_FLAGS) \
> > 
> > I suppose that this simple patch may lead to some undesirable side effects.
> 
> One side effect is that this gets even less readable.

Yes, you are right :)

> Another one would be that two dts filenames which only differ in the
> usage of '.' and '_' would result in the same define, but I think that
> case is negligible as this define is unused in barebox itself. It could
                                       ^^^^^^^^^^^^^^^^^^^^^^^^
> be used by external dts fragments passed in via CONFIG_EXTERNAL_DTS_FRAGMENTS.
> 
> Other than that, what side effects are you afraid of?

I have an idea that someone relies on these *_dts macros.

Now I see (as you have noted above) that there is no macro users in mainline source tree:

  $ git grep -w .*_dts
  common/Kconfig:   #ifdef foo_board_dts
  scripts/Makefile.lib:cmd_dtc = /usr/bin/env echo -e '$(pound)define $(subst -,_,$(*F))_dts 1\n'$(foreach f,$< $(dts-frags),'$(pound)include "$(f)"\n') | \

-- 
Best regards,
  Antony Pavlov