Re: [PATCH] perf tools: Fix linking errors with --as-needed flag

[Tom Zanussi <tzanussi@gmail.com>]

On Sun, 2010-08-22 at 01:43 -0500, Tom Zanussi wrote:
> Hi,
> 
> On Sat, 2010-08-21 at 14:24 -0300, Arnaldo Carvalho de Melo wrote:
> > Em Sun, Jul 18, 2010 at 02:04:32PM +0300, Ozan Çağlayan escreveu:
> > > On 18.07.2010 13:45, Ozan Çağlayan wrote:
> > > > External shared libraries should never be appended to the LDFLAGS as
> > > > this messes the linking order. As EXTLIBS collects those libraries,
> > > > it seems that perl and python libraries  should also be appended
> > > > to EXTLIBS.
> > > > 
> > > > Also fix the broken linking order.
> > > 
> > > Hm actually the PERL_EMBED_LDOPTS may contain LDFLAGS and LIBADD according
> > > to distribution's perl package configuration's goodness/badness. On my system
> > > the return value is crap which bloats the linking process:
> > > 
> > >  -rdynamic -Wl,-rpath,/usr/lib/perl5/5.10.1/i686-linux-thread-multi/CORE  -fstack-protector -L/usr/local/lib  -L/usr/lib/perl5/5.10.1/i686-linux-thread-multi/CORE -lperl -lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
> > > 
> > > PYTHON_EMBED_LDOPTS evaluates python-config --ldflags and adds these to 
> > > ALL_LDFLAGS. (--libs and --ldflags are synonyms for python-config). According
> > > to python-config this code *never* returns LDFLAGS so it's safe to put them in
> > > EXTLIBS.
> > > 
> > > So the cure may be more than this patch for perl stuff, but at least it fixes my
> > > linking problems with -Wl, --as-needed.
> > 
> > Can you refresh this patch? I had it in the back of my mind, remembered
> > it when considering a similar patch by Kirill, but his covers just the
> > python case.
> > 
> > Tom, can you please check Ozan's and Kirill's patches and tell me if I
> > can stick your Acked-by to them?
> > 
> 
> I refreshed Ozan's patch against tip and tried both with and without
> -Wl,--as-needed and it worked fine for both Perl and Python, on my
> Ubuntu 9.10 system.  The refreshed patch I used is included below.
> 
> It wasn't clear to me whether Ozan's PERL_EMBED_LDOPTS output still
> caused link errors; here's mine, which didn't:
> 
> trz@tropicana:~$ perl -MExtUtils::Embed -e ldopts
> -Wl,-E  -L/usr/local/lib  -L/usr/lib/perl/5.10/CORE -lperl -ldl -lm
> -lpthread -lc -lcrypt
> 
> In any case, since neither ExtUtils::Embed nor python-config seem to
> have a way to get the LDFLAGS and LIBADD components separately, we'll
> have to find some other way to do that if necessary.
> 

Looking into it a bit further, both ExtUtils::Embed -e ldopts and
python-config --ldflags put the libs at the end, so we should be able to
parse the output of those and take only the parts we need for each
component.  How about something like this instead?

Tom 

---

[PATCH] Refresh of Ozan Çağlayan's patch: perf tools: Fix linking errors
with --as-needed flag:

External shared libraries should never be appended to the LDFLAGS as
this messes the linking order. As EXTLIBS collects those libraries,
it seems that perl and python libraries  should also be appended
to EXTLIBS.

Also fix the broken linking order.

v2: add commands to separate out LDFLAGS and libs from both Perl and
Python LDOPTS (Tom Zanussi)

Signed-off-by: Tom Zanussi <tzanussi@gmail.com>
---
 tools/perf/Makefile |   14 ++++++++++----
 1 files changed, 10 insertions(+), 4 deletions(-)

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 26a3f2e..59f5b10 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -589,13 +589,16 @@ ifdef NO_LIBPERL
 	BASIC_CFLAGS += -DNO_LIBPERL
 else
 	PERL_EMBED_LDOPTS = `perl -MExtUtils::Embed -e ldopts 2>/dev/null`
+	PERL_EMBED_LDFLAGS = $(shell echo $(PERL_EMBED_LDOPTS) | sed 's/-l.*//' )
+	PERL_EMBED_LIBADD = $(shell echo $(PERL_EMBED_LDOPTS) | grep -o '\-l.*' )
 	PERL_EMBED_CCOPTS = `perl -MExtUtils::Embed -e ccopts 2>/dev/null`
 	FLAGS_PERL_EMBED=$(PERL_EMBED_CCOPTS) $(PERL_EMBED_LDOPTS)
 
 	ifneq ($(call try-cc,$(SOURCE_PERL_EMBED),$(FLAGS_PERL_EMBED)),y)
 		BASIC_CFLAGS += -DNO_LIBPERL
 	else
-		ALL_LDFLAGS += $(PERL_EMBED_LDOPTS)
+		ALL_LDFLAGS += $(PERL_EMBED_LDFLAGS)
+		EXTLIBS += $(PERL_EMBED_LIBADD)
 		LIB_OBJS += $(OUTPUT)util/scripting-engines/trace-event-perl.o
 		LIB_OBJS += $(OUTPUT)scripts/perl/Perf-Trace-Util/Context.o
 	endif
@@ -605,12 +608,15 @@ ifdef NO_LIBPYTHON
 	BASIC_CFLAGS += -DNO_LIBPYTHON
 else
 	PYTHON_EMBED_LDOPTS = `python-config --ldflags 2>/dev/null`
+	PYTHON_EMBED_LDFLAGS = $(shell echo $(PYTHON_EMBED_LDOPTS) | sed 's/-l.*//' )
+	PYTHON_EMBED_LIBADD = $(shell echo $(PYTHON_EMBED_LDOPTS) | grep -o '\-l.*' )
 	PYTHON_EMBED_CCOPTS = `python-config --cflags 2>/dev/null`
 	FLAGS_PYTHON_EMBED=$(PYTHON_EMBED_CCOPTS) $(PYTHON_EMBED_LDOPTS)
 	ifneq ($(call try-cc,$(SOURCE_PYTHON_EMBED),$(FLAGS_PYTHON_EMBED)),y)
 		BASIC_CFLAGS += -DNO_LIBPYTHON
 	else
-		ALL_LDFLAGS += $(PYTHON_EMBED_LDOPTS)
+		ALL_LDFLAGS += $(PYTHON_EMBED_LDFLAGS)
+		EXTLIBS += $(PYTHON_EMBED_LIBADD)
 		LIB_OBJS += $(OUTPUT)util/scripting-engines/trace-event-python.o
 		LIB_OBJS += $(OUTPUT)scripts/python/Perf-Trace-Util/Context.o
 	endif
@@ -919,8 +925,8 @@ $(OUTPUT)perf.o: perf.c $(OUTPUT)common-cmds.h $(OUTPUT)PERF-CFLAGS
 		$(ALL_CFLAGS) -c $(filter %.c,$^) -o $@
 
 $(OUTPUT)perf$X: $(OUTPUT)perf.o $(BUILTIN_OBJS) $(PERFLIBS)
-	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) -o $@ $(OUTPUT)perf.o \
-		$(BUILTIN_OBJS) $(ALL_LDFLAGS) $(LIBS)
+	$(QUIET_LINK)$(CC) $(ALL_CFLAGS) $(ALL_LDFLAGS) $(OUTPUT)perf.o \
+		$(BUILTIN_OBJS) $(LIBS) -o $@
 
 $(OUTPUT)builtin-help.o: builtin-help.c $(OUTPUT)common-cmds.h $(OUTPUT)PERF-CFLAGS
 	$(QUIET_CC)$(CC) -o $@ -c $(ALL_CFLAGS) \
-- 
1.6.4.GIT