linux-kernel - Re: [PATCH v2] Fix objtool with clang

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Message-ID: <20161129095841.GA31494@krava>
Date:   Tue, 29 Nov 2016 10:58:41 +0100
From:   Jiri Olsa <jolsa@...hat.com>
To:     Arnaldo Carvalho de Melo <acme@...hat.com>
Cc:     Peter Foley <pefoley2@...oley.com>,
        LKML <linux-kernel@...r.kernel.org>, wangnan0@...wei.com
Subject: Re: [PATCH v2] Fix objtool with clang

On Tue, Nov 29, 2016 at 10:32:24AM +0100, Jiri Olsa wrote:
> On Mon, Nov 28, 2016 at 05:40:46PM -0200, Arnaldo Carvalho de Melo wrote:
> 
> SNIP
> 
> >   LD       /tmp/build/perf/pmu-events/pmu-events-in.o
> >   CC       /tmp/build/perf/arch/x86/util/intel-bts.o
> >   CC       /tmp/build/perf/builtin-buildid-cache.o
> >   CC       /tmp/build/perf/builtin-list.o
> >   LD       /tmp/build/perf/arch/x86/util/libperf-in.o
> >   MKDIR    /tmp/build/perf/arch/x86/tests/
> >   CC       /tmp/build/perf/arch/x86/tests/regs_load.o
> > /tmp/build/perf/.plugin_jbd2.o.cmd:3: *** empty variable name.  Stop.
> > Makefile:192: recipe for target '/tmp/build/perf/plugin_jbd2-in.o' failed
> > make[2]: *** [/tmp/build/perf/plugin_jbd2-in.o] Error 2
> > Makefile.perf:591: recipe for target '/tmp/build/perf/libtraceevent-dynamic-list' failed
> > make[1]: *** [/tmp/build/perf/libtraceevent-dynamic-list] Error 2
> > make[1]: *** Waiting for unfinished jobs....
> 
> ok, reproduced..
> 
> the commit changes the output of the depfile for some reason,
> and our fixdep does not handle it correctly and produce wrong
> cmd file that failed to parse.. checking for fix
> 
> depfile changes ('+' is after the change):
> 
> -plugin_jbd2.o: plugin_jbd2.c /usr/include/stdc-predef.h \
> +plugin_jbd2.o plugin_jbd2.o: plugin_jbd2.c /usr/include/stdc-predef.h \
> 
> jirka

so Fedora 25 puts old target name in the generated dependencies
in case you split the -Wp options.. while Fedora 24 the old way

and both F24 and F25 shows me same gcc version 6.2.1
(note that just the first command output with 2 targets is wrong for us)

Fedora 25:
[root@...el-denlow-r-02 ~]# gcc -o ex.o -c -Wp,-MD,krava -Wp,-MT,krava -g ex.c
[root@...el-denlow-r-02 ~]# cat krava
ex.o krava: ex.c /usr/include/stdc-predef.h /usr/include/stdio.h \
 /usr/include/features.h /usr/include/sys/cdefs.h \
 /usr/include/bits/wordsize.h /usr/include/gnu/stubs.h \
 /usr/include/gnu/stubs-64.h \
 /usr/lib/gcc/x86_64-redhat-linux/6.2.1/include/stddef.h \
 /usr/include/bits/types.h /usr/include/bits/typesizes.h \
 /usr/include/libio.h /usr/include/_G_config.h /usr/include/wchar.h \
 /usr/lib/gcc/x86_64-redhat-linux/6.2.1/include/stdarg.h \
 /usr/include/bits/stdio_lim.h /usr/include/bits/sys_errlist.h

[root@...el-denlow-r-02 ~]# gcc -o ex.o -c -Wp,-MD,krava,-MT,krava -g ex.c
[root@...el-denlow-r-02 ~]# cat krava
krava: ex.c /usr/include/stdc-predef.h /usr/include/stdio.h \
 /usr/include/features.h /usr/include/sys/cdefs.h \
 /usr/include/bits/wordsize.h /usr/include/gnu/stubs.h \
 /usr/include/gnu/stubs-64.h \
 /usr/lib/gcc/x86_64-redhat-linux/6.2.1/include/stddef.h \
 /usr/include/bits/types.h /usr/include/bits/typesizes.h \
 /usr/include/libio.h /usr/include/_G_config.h /usr/include/wchar.h \
 /usr/lib/gcc/x86_64-redhat-linux/6.2.1/include/stdarg.h \
 /usr/include/bits/stdio_lim.h /usr/include/bits/sys_errlist.h


Fedora 24:
[jolsa@...va trash]$ gcc -o ex.o -c -Wp,-MD,krava -Wp,-MT,krava -g ex.c
[jolsa@...va trash]$ cat krava
krava: ex.c /usr/include/stdc-predef.h /usr/include/stdio.h \
 /usr/include/features.h /usr/include/sys/cdefs.h \
 /usr/include/bits/wordsize.h /usr/include/gnu/stubs.h \
 /usr/include/gnu/stubs-64.h \
 /usr/lib/gcc/x86_64-redhat-linux/6.2.1/include/stddef.h \
 /usr/include/bits/types.h /usr/include/bits/typesizes.h \
 /usr/include/libio.h /usr/include/_G_config.h /usr/include/wchar.h \
 /usr/lib/gcc/x86_64-redhat-linux/6.2.1/include/stdarg.h \
 /usr/include/bits/stdio_lim.h /usr/include/bits/sys_errlist.h

[jolsa@...va trash]$ gcc -o ex.o -c -Wp,-MD,krava-Wp,-MT,krava -g ex.c
[jolsa@...va trash]$ cat krava
krava: ex.c /usr/include/stdc-predef.h /usr/include/stdio.h \
 /usr/include/features.h /usr/include/sys/cdefs.h \
 /usr/include/bits/wordsize.h /usr/include/gnu/stubs.h \
 /usr/include/gnu/stubs-64.h \
 /usr/lib/gcc/x86_64-redhat-linux/6.2.1/include/stddef.h \
 /usr/include/bits/types.h /usr/include/bits/typesizes.h \
 /usr/include/libio.h /usr/include/_G_config.h /usr/include/wchar.h \
 /usr/lib/gcc/x86_64-redhat-linux/6.2.1/include/stdarg.h \
 /usr/include/bits/stdio_lim.h /usr/include/bits/sys_errlist.h


I'll make fixdep to deal with that and try to have someone from gcc to clarify on this

jirka