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Date:   Fri, 30 Mar 2018 22:11:09 -0700
From:   Andrei Vagin <avagin@virtuozzo.com>
To:     Masahiro Yamada <yamada.masahiro@socionext.com>
Cc:     Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Sam Ravnborg <sam@ravnborg.org>,
        Michal Marek <michal.lkml@markovi.net>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Frank Rowand <frank.rowand@sony.com>,
        Geert Uytterhoeven <geert@linux-m68k.org>
Subject: Re: [03/10] genksyms: generate lexer and parser during build instead
 of shipping
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On Sat, Mar 31, 2018 at 11:20:22AM +0900, Masahiro Yamada wrote:
> 2018-03-31 7:21 GMT+09:00 Andrei Vagin <avagin@virtuozzo.com>:
> > On Fri, Mar 30, 2018 at 10:40:22AM -0700, Andrei Vagin wrote:
> >> On Fri, Mar 23, 2018 at 10:04:32PM +0900, Masahiro Yamada wrote:
> >> > Now that the kernel build supports flex and bison, remove the _shipped
> >> > files and generate them during the build instead.
> >> >
> >> > There are no more shipped lexer and parser, so I ripped off the rules
> >> > in scripts/Malefile.lib that were used for REGENERATE_PARSERS.
> >> >
> >> > The genksyms parser has ambiguous grammar, which would emit warnings:
> >> >
> >> >  scripts/genksyms/parse.y: warning: 9 shift/reduce conflicts [-Wconflicts-sr]
> >> >  scripts/genksyms/parse.y: warning: 5 reduce/reduce conflicts [-Wconflicts-rr]
> >> >
> >> > They are normally suppressed, but displayed when W=1 is given.
> >> >
> >> > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> >> > ---
> >> >
> >> >  scripts/Makefile.lib                 |   24 +-
> >> >  scripts/genksyms/Makefile            |   23 +
> >> >  scripts/genksyms/lex.lex.c_shipped   | 2291 --------------------------------
> >> >  scripts/genksyms/parse.tab.c_shipped | 2394 ----------------------------------
> >> >  scripts/genksyms/parse.tab.h_shipped |  119 --
> >> >  5 files changed, 26 insertions(+), 4825 deletions(-)
> >> >  delete mode 100644 scripts/genksyms/lex.lex.c_shipped
> >> >  delete mode 100644 scripts/genksyms/parse.tab.c_shipped
> >> >  delete mode 100644 scripts/genksyms/parse.tab.h_shipped
> >> >
> >> > diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
> >> > index 2fde810..b7d2c97 100644
> >> > --- a/scripts/Makefile.lib
> >> > +++ b/scripts/Makefile.lib
> >> > @@ -183,14 +183,8 @@ endef
> >> >  quiet_cmd_flex = LEX     $@
> >> >        cmd_flex = $(LEX) -o$@ -L $<
> >> >
> >> > -ifdef REGENERATE_PARSERS
> >> > -.PRECIOUS: $(src)/%.lex.c_shipped
> >> > -$(src)/%.lex.c_shipped: $(src)/%.l
> >> > -   $(call cmd,flex)
> >> > -endif
> >> > -
> >> >  .PRECIOUS: $(obj)/%.lex.c
> >> > -$(filter %.lex.c,$(targets)): $(obj)/%.lex.c: $(src)/%.l FORCE
> >> > +$(obj)/%.lex.c: $(src)/%.l FORCE
> >> >     $(call if_changed,flex)
> >> >
> >> >  # YACC
> >> > @@ -198,27 +192,15 @@ $(filter %.lex.c,$(targets)): $(obj)/%.lex.c: $(src)/%.l FORCE
> >> >  quiet_cmd_bison = YACC    $@
> >> >        cmd_bison = $(YACC) -o$@ -t -l $<
> >> >
> >> > -ifdef REGENERATE_PARSERS
> >> > -.PRECIOUS: $(src)/%.tab.c_shipped
> >> > -$(src)/%.tab.c_shipped: $(src)/%.y
> >> > -   $(call cmd,bison)
> >> > -endif
> >> > -
> >> >  .PRECIOUS: $(obj)/%.tab.c
> >> > -$(filter %.tab.c,$(targets)): $(obj)/%.tab.c: $(src)/%.y FORCE
> >> > +$(obj)/%.tab.c: $(src)/%.y FORCE
> >> >     $(call if_changed,bison)
> >> >
> >> >  quiet_cmd_bison_h = YACC    $@
> >> >        cmd_bison_h = bison -o/dev/null --defines=$@ -t -l $<
> >> >
> >> > -ifdef REGENERATE_PARSERS
> >> > -.PRECIOUS: $(src)/%.tab.h_shipped
> >> > -$(src)/%.tab.h_shipped: $(src)/%.y
> >> > -   $(call cmd,bison_h)
> >> > -endif
> >> > -
> >> >  .PRECIOUS: $(obj)/%.tab.h
> >> > -$(filter %.tab.h,$(targets)): $(obj)/%.tab.h: $(src)/%.y FORCE
> >> > +$(obj)/%.tab.h: $(src)/%.y FORCE
> >> >     $(call if_changed,bison_h)
> >> >
> >> >  # Shipped files
> >> > diff --git a/scripts/genksyms/Makefile b/scripts/genksyms/Makefile
> >> > index 0ccac51..f4749e8 100644
> >> > --- a/scripts/genksyms/Makefile
> >> > +++ b/scripts/genksyms/Makefile
> >> > @@ -5,9 +5,32 @@ always             := $(hostprogs-y)
> >> >
> >> >  genksyms-objs      := genksyms.o parse.tab.o lex.lex.o
> >> >
> >> > +# FIXME: fix the ambiguous grammar in parse.y and delete this hack
> >> > +#
> >> > +# Suppress shift/reduce, reduce/reduce conflicts warnings
> >> > +# unless W=1 is specified.
> >> > +ifeq ($(findstring 1,$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
> >> > +SUPPRESS_BISON_WARNING := 2>/dev/null
> >>
> >> We have a robot which runs CRIU tests on linux-next.
> >> Yesterday it failed with this error:
> >>
> >>   HOSTCC  scripts/genksyms/genksyms.o
> >> make[2]: *** [scripts/genksyms/parse.tab.c] Error 127
> >>
> >> cripts/genksyms/Makefile:20: recipe for target 'scripts/genksyms/parse.tab.c' failed
> >> scripts/Makefile.build:559: recipe for target 'scripts/genksyms' failed
> >> Makefile:1073: recipe for target 'scripts' failed
> >> make[1]: *** [scripts/genksyms] Error 2
> >> make: *** [scripts] Error 2
> >> make: *** Waiting for unfinished jobs....
> >>
> >> https://travis-ci.org/avagin/linux/jobs/360056903
> >>
> >> From this output, it is very hard to understand what was going wrong.
> >
> >
> > The reason was that bison and fles were not installed, but I think the
> > error message should be more clear.
> >
> >>
> >> Thanks,
> >> Andrei
> >>
> 
> Thanks for the report.
> 
> 
> OK, I will apply the fix-up attached below.
> 
> If bison is not installed, it will fail with clear message.

Thank you!

> 
>   HOSTCC  scripts/genksyms/genksyms.o
> /bin/sh: 1: bison: not found
> make[2]: *** [scripts/genksyms/Makefile:18:
> scripts/genksyms/parse.tab.c] Error 127
> make[1]: *** [scripts/Makefile.build:559: scripts/genksyms] Error 2
> make: *** [Makefile:1073: scripts] Error 2
> 
> 
> BTW, without flex and bison, how did you build Kconfig?

A config is created on the host, but a kernel is compiled in a docker
container. Maybe bison was installed on the host.

We do something like this:

$ make olddefconfig
$ make localyesconfig
$ docker run -v /home/travis/build/avagin/linux:/mnt/kernel -v
/home/travis/.ccache:/mnt/ccache -w /mnt/kernel criu-kernel make -j 4

> 
> Since commit 29c833061c1d8c2d1d23a62e7061561eadd76cdb,
> Kconfig requires flex and bison, and this commit is
> in Linus' tree for a couple of month.
> 
> Without flex and bison, you cannot do even "make *config"
> Nobody has ever complaint about this.
> 
> 
> 
> 
> diff --git a/scripts/genksyms/Makefile b/scripts/genksyms/Makefile
> index aeefd47..7cb3d70 100644
> --- a/scripts/genksyms/Makefile
> +++ b/scripts/genksyms/Makefile
> @@ -10,20 +10,20 @@ genksyms-objs       := genksyms.o parse.tab.o lex.lex.o
>  # Suppress shift/reduce, reduce/reduce conflicts warnings
>  # unless W=1 is specified.
>  ifeq ($(findstring 1,$(KBUILD_ENABLE_EXTRA_GCC_CHECKS)),)
> -SUPPRESS_BISON_WARNING := 2>/dev/null
> -endif
> 
>  quiet_cmd_bison_no_warn = $(quet_cmd_bison)
> -      cmd_bison_no_warn = $(cmd_bison) $(SUPPRESS_BISON_WARNING)
> +      cmd_bison_no_warn = $(YACC) --version >/dev/null; $(cmd_bison)
> 2>/dev/null
> 
>  $(obj)/parse.tab.c: $(src)/parse.y FORCE
>         $(call if_changed,bison_no_warn)
> 
>  quiet_cmd_bison_h_no_warn = $(quet_cmd_bison_h)
> -      cmd_bison_h_no_warn = $(cmd_bison_h) $(SUPPRESS_BISON_WARNING)
> +      cmd_bison_h_no_warn = $(YACC) --version >/dev/null;
> $(cmd_bison_h) 2>/dev/null
> 
>  $(obj)/parse.tab.h: $(src)/parse.y FORCE
>         $(call if_changed,bison_h_no_warn)
> +
> +endif
>  # FIXME END
> 
>  # -I needed for generated C source (shipped source)
> 
> 
> -- 
> Best Regards
> Masahiro Yamada