Re: [PATCH] kbuild: Do not use hyphen in exported variable name

[Ben Hutchings <ben@decadent.org.uk>]

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On Sun, 2017-04-30 at 15:49 +0100, Ben Hutchings wrote:
> On Sun, 2017-04-30 at 23:14 +0900, Masahiro Yamada wrote:
> > Hi Ben,
> > 
> > 
> > > 2017-04-23 16:23 GMT+09:00 Ben Hutchings <ben@decadent.org.uk>:
> > > On Sun, 2017-04-23 at 15:47 +0900, Masahiro Yamada wrote:
> > > [...]
> > > > I tested dtbs_install once again by myself, but
> > > > dtbinst-root is exported to the sub make
> > > > and the vendor directories are created correctly.
> > > > 
> > > > 
> > > > I checked the debian's forum you gave
> > > > > References: https://bugs.debian.org/833561
> > > > 
> > > > In there, you mentioned:
> > > > "This looks like a bug in make, but we can at least work around it by
> > > > using a non-hyphenated variable name."
> > > > 
> > > > 
> > > > Does this issue happen on a specific Make version?
> > > > 
> > > > I tested GNU make 3.81, 3.82, 4.0, 4.1, 4.2,
> > > > but I was not hit by the problem.
> > > 
> > > I don't think this is make version dependent.  I can't reproduce the
> > > issue today with make 4.1.  But I would have been using the same
> > > version in August when I wrote that.
> > > 
> > > What more can I say?  Clearly the hyphenated variable gets passed to
> > > the sub-make in most cases.  But it's not totally reliable because last
> > > year it wasn't working for us.
> > > 
> > > > In the last post in the thread, you concluded:
> > > > "We believe that the bug you reported is fixed in the latest version of
> > > > linux, which is due to be installed in the Debian FTP archive."
> > > 
> > > I didn't write that, it's a standard message generated for bugs marked
> > > as closed in a package changelog. :-)
> > > 
> > > > If so, why is this patch here?
> > > > How is the dtbs_install procedure different in the Debian package?
> > > 
> > > This is the patch I applied to the package.
> > > 
> > 
> > Do you still need this patch for Debian?
> [...]
> 
> I don't think so.  I just don't know for sure.

I've now seen a similar problem with the suffix-y variable exported
from arch/sh/boot/Makefile to arch/sh/boot/compressed/Makefile:
https://buildd.debian.org/status/fetch.php?pkg=linux&arch=sh4&ver=4.13%7Erc5-1%7Eexp1&stamp=1502943967&raw=0

Those Makefiles haven't changed recently, so there must be some
difference in the build environment.  Here's a Makefile that
demonstrates the difference in behaviour between bash and dash:

--- BEGIN ---
ifdef WANTED_SHELL
SHELL := $(WANTED_SHELL)
endif

test:
	@WANTED_SHELL=/bin/bash $(MAKE) test2
	@WANTED_SHELL=/bin/dash $(MAKE) test2
	@WANTED_SHELL= $(MAKE) test2

test2: export foo_bar := foo_bar
test2: export foo-bar := foo-bar
test2:
	@echo SHELL=$(SHELL)
	@$(MAKE) test3

test3:
	@echo foo_bar=$(foo_bar)
	@echo foo-bar=$(foo-bar)

.PHONY: test test2 test3
--- END ---

For me, this produces:

$ make -s
SHELL=/bin/bash
foo_bar=foo_bar
foo-bar=foo-bar
SHELL=/bin/dash
foo_bar=foo_bar
foo-bar=
SHELL=/bin/sh
foo_bar=foo_bar
foo-bar=foo-bar

Note that the last two cases are different even though /bin/sh is dash
here.  It turns out that make avoids using the shell for simple
commands, unless it has been changed from the default:
https://sources.debian.net/src/make-dfsg/4.1-9.1/job.c/#L2575

Ben.

-- 
Ben Hutchings
The generation of random numbers is too important to be left to chance.
                                                       - Robert Coveyou

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