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

["Kirill A. Shutemov" <kirill@shutemov.name>]

On Sun, Aug 22, 2010 at 09:44:13PM -0500, Tom Zanussi wrote:
> 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>

Tested-by: Kirill A. Shutemov <kirill@shutemov.name>

But, probably better to do it with make:

diff --git a/tools/perf/Makefile b/tools/perf/Makefile
index 4f1fa77..03a53a9 100644
--- a/tools/perf/Makefile
+++ b/tools/perf/Makefile
@@ -313,6 +313,9 @@ TEST_PROGRAMS =
 
 SCRIPT_SH += perf-archive.sh
 
+grep-libs = $(filter -l%,$(1))
+strip-libs = $(filter-out -l%,$(1))
+
 #
 # No Perl scripts right now:
 #
@@ -588,14 +591,17 @@ endif
 ifdef NO_LIBPERL
        BASIC_CFLAGS += -DNO_LIBPERL
 else
-       PERL_EMBED_LDOPTS = `perl -MExtUtils::Embed -e ldopts 2>/dev/null`
+       PERL_EMBED_LDOPTS = $(shell perl -MExtUtils::Embed -e ldopts 2>/dev/null)
+       PERL_EMBED_LDFLAGS = $(call strip-libs,$(PERL_EMBED_LDOPTS))
+       PERL_EMBED_LIBADD = $(call grep-libs,$(PERL_EMBED_LDOPTS))
        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
@@ -604,13 +610,16 @@ endif
 ifdef NO_LIBPYTHON
        BASIC_CFLAGS += -DNO_LIBPYTHON
 else
-       PYTHON_EMBED_LDOPTS = `python-config --ldflags 2>/dev/null`
+       PYTHON_EMBED_LDOPTS = $(shell python-config --ldflags 2>/dev/null)
+       PYTHON_EMBED_LDFLAGS = $(call strip-libs,$(PYTHON_EMBED_LDOPTS))
+       PYTHON_EMBED_LIBADD = $(call grep-libs,$(PYTHON_EMBED_LDOPTS))
        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
@@ -910,8 +919,8 @@ $(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) \
-- 
 Kirill A. Shutemov