linux-kernel - Re: [PATCH v6 5/8] kbuild: add fine grained build dependencies for exported symbols

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Date:	Tue, 15 Mar 2016 19:14:38 -0400 (EDT)
From:	Nicolas Pitre <nicolas.pitre@...aro.org>
To:	Michal Marek <mmarek@...e.com>, Michal Marek <mmarek@...e.cz>
cc:	linux-kbuild@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v6 5/8] kbuild: add fine grained build dependencies for
 exported symbols

On Tue, 15 Mar 2016, Michal Marek wrote:

> Dne 14.3.2016 v 03:42 Nicolas Pitre napsal(a):
> > +# Filter out exported kernel symbol names from the preprocessor output.
> > +# See also __KSYM_DEPS__ in include/linux/export.h.
> > +# We disable the depfile generation here, so as not to overwrite the existing
> > +# depfile while fixdep is parsing it
> > +flags_nodeps = $(filter-out -Wp$(comma)-M%, $($(1)))
> > +ksym_dep_filter =                                                            \
> > +	case "$(1)" in                                                       \
> > +	cc_*_c) $(CPP) $(call flags_nodeps,c_flags) -D__KSYM_DEPS__ $< ;;    \
> > +	as_*_S) $(CPP) $(call flags_nodeps,a_flags) -D__KSYM_DEPS__ $< ;;    \
> > +	cpp_lds_S) : ;;                                                      \
> > +	*) echo "Don't know how to preprocess $(1)" >&2; false ;;            \
> > +	esac | sed -rn 's/^.*=== __KSYM_(.*) ===.*$$/KSYM_\1/p'
> > +
> > +cmd_and_fixdep =                                                             \
> > +	$(echo-cmd) $(cmd_$(1));                                             \
> > +	$(ksym_dep_filter) |                                                 \
> > +		scripts/basic/fixdep -e $(depfile) $@ '$(make-cmd)'          \
> > +			> $(dot-target).tmp;	                             \
> > +	rm -f $(depfile);                                                    \
> > +	mv -f $(dot-target).tmp $(dot-target).cmd;
> > +
> > +endif
> 
> Not sure what happened this time, but I got
> 
> drivers/md/.dm-round-robin.mod.o.cmd:5: *** unterminated call to
> function 'wildcard': missing ')'.  Stop.
> 
> The depfile is indeed corrupt (truncated):
> tail drivers/md/.dm-round-robin.mod.o.cmd
>   arch/x86/include/asm/disabled-features.h \
>     $(wildcard include/config/x86/intel/mpx.h) \
>   arch/x86/include/asm/rmwcc.h \
>   arch/x86/include/asm/barrier.h \
>     $(wildcard include/config/x86/ppro/fence.h) \
>   arch/x86/include/asm/nops.h \
>     $(wildcard include/config/mk7.h) \
>   include/asm-generic/barrier.h \
>   include/asm-generic/bitops/find.h \
>     $(wildcard include/config/generic/
> 
> The file is exactly 8kB long:
> $ ls -l drivers/md/.dm-round-robin.mod.o.cmd
> -rw-r--r-- 1 mmarek users 8192 Mar  8 13:33
> drivers/md/.dm-round-robin.mod.o.cmd

[...]

> Forgot to add: This was an allmodconfig build without
> CONFIG_TRIM_UNUSED_SYMS.

If CONFIG_TRIM_UNUSED_SYMS is actually not selected, then I really don't 
see how my changes can be involved in this failure.

And I cannot reproduce here so far. I didn't receive anything from 
kbuild test robot since February 15 either. Is this something that you 
are able to reproduce on your side?

If so, do you get suspicious output on stderr during the build?  Maybe 
fixdep exits prematurelywith "fixdep: bad data on stdin"?  However, that 
cannot happen if CONFIG_TRIM_UNUSED_SYMS=n.

Did you test my git branch, or did you apply the posted patches to your 
tree?  If the later, could you publish a branch for it so I could test 
the same tree as you do?


Nicolas