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

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Date:   Tue, 29 Nov 2016 15:28:08 +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 Mon, Nov 28, 2016 at 05:40:46PM -0200, Arnaldo Carvalho de Melo wrote:

SNIP

>   CC       /tmp/build/perf/builtin-buildid-list.o
>   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....
>   MKDIR    /tmp/build/perf/arch/x86/tests/
>   CC       /tmp/build/perf/arch/x86/tests/arch-tests.o
> <SNIP>
>   CC       /tmp/build/perf/util/pmu.o
>   CC       /tmp/build/perf/util/pmu-flex.o
>   LD       /tmp/build/perf/util/libperf-in.o
>   LD       /tmp/build/perf/libperf-in.o
> Makefile:108: recipe for target 'install-bin' failed
> make: *** [install-bin] Error 2
> make: Leaving directory '/home/acme/git/linux/tools/perf'
> [acme@...et linux]$ 

how about following fix.. it gets rid of the -Wp,MT option completely
so it should address Peter's issue.. it also makes fixdep more robust
and makes it wait for first target before spitting out dependencies

I have some difficulties now with getting Fedora 25.. I'll test
and send this out within this week

jirka


---
diff --git a/tools/build/Build.include b/tools/build/Build.include
index c4ae12a5d0a5..63c898f089f7 100644
--- a/tools/build/Build.include
+++ b/tools/build/Build.include
@@ -89,12 +89,12 @@ if_changed = $(if $(strip $(any-prereq) $(arg-check)),             \
 # - per target C flags
 # - per object C flags
 # - BUILD_STR macro to allow '-D"$(variable)"' constructs
-c_flags_1 = -Wp,-MD,$(depfile),-MT,$@ $(CFLAGS) -D"BUILD_STR(s)=\#s" $(CFLAGS_$(basetarget).o) $(CFLAGS_$(obj))
+c_flags_1 = -Wp,-MD,$(depfile) $(CFLAGS) -D"BUILD_STR(s)=\#s" $(CFLAGS_$(basetarget).o) $(CFLAGS_$(obj))
 c_flags_2 = $(filter-out $(CFLAGS_REMOVE_$(basetarget).o), $(c_flags_1))
 c_flags   = $(filter-out $(CFLAGS_REMOVE_$(obj)), $(c_flags_2))
-cxx_flags = -Wp,-MD,$(depfile),-MT,$@ $(CXXFLAGS) -D"BUILD_STR(s)=\#s" $(CXXFLAGS_$(basetarget).o) $(CXXFLAGS_$(obj))
+cxx_flags = -Wp,-MD,$(depfile) $(CXXFLAGS) -D"BUILD_STR(s)=\#s" $(CXXFLAGS_$(basetarget).o) $(CXXFLAGS_$(obj))
 
 ###
 ## HOSTCC C flags
 
-host_c_flags = -Wp,-MD,$(depfile),-MT,$@ $(CHOSTFLAGS) -D"BUILD_STR(s)=\#s" $(CHOSTFLAGS_$(basetarget).o) $(CHOSTFLAGS_$(obj))
+host_c_flags = -Wp,-MD,$(depfile) $(CHOSTFLAGS) -D"BUILD_STR(s)=\#s" $(CHOSTFLAGS_$(basetarget).o) $(CHOSTFLAGS_$(obj))
diff --git a/tools/build/fixdep.c b/tools/build/fixdep.c
index 1521d36cef0d..734d1547cbae 100644
--- a/tools/build/fixdep.c
+++ b/tools/build/fixdep.c
@@ -49,7 +49,7 @@ static void parse_dep_file(void *map, size_t len)
 	char *end = m + len;
 	char *p;
 	char s[PATH_MAX];
-	int is_target;
+	int is_target, has_target = 0;
 	int saw_any_target = 0;
 	int is_first_dep = 0;
 
@@ -67,7 +67,8 @@ static void parse_dep_file(void *map, size_t len)
 		if (is_target) {
 			/* The /next/ file is the first dependency */
 			is_first_dep = 1;
-		} else {
+			has_target = 1;
+		} else if (has_target) {
 			/* Save this token/filename */
 			memcpy(s, m, p-m);
 			s[p - m] = 0;