PLDWWW: DevelopingPLD/AdvancedDeveloping/FixingAsNeeded
sparky
sparky at pld-linux.org
Mon Aug 7 01:19:08 CEST 2006
Author: sparky Date: Sun Aug 6 23:19:08 2006 GMT
Module: PLDWWW URL: http://www.pld-linux.org/DevelopingPLD/AdvancedDeveloping/FixingAsNeeded
---- Log message:
Created from my posts on pld-devel-en list, needs a lot of work
---- Page affected: DevelopingPLD/AdvancedDeveloping/FixingAsNeeded
---- Diffs:
================================================================
New page:
#language en
= Fixing --as-needed problems =
=== Quick Workaround ===
Put in spec file this line:
{{{
%devine filterout_ld -Wl,--as-needed
}}}
But '''don't use it''' unless you realy need.
Why ? Because it's very stupid. If something fails to build normally
it's a sign {{{--as-needed}}} did well it's job and disabled unneeded
libraries.
== How --as-needed works ==
With {{{--as-needed}}} enabled only libraries which contain symbols required by
__object files__ are linked.
===== About positions =====
Linker options are positional, and position is very important.
Correct ones are:
{{{
$ gcc $(LDFLAGS) -o $@ $(OBJECTS) $(LIBS)
}}}
and this generally works well.
If there is something like that:
{{{
$ gcc -Wl,--as-needed -l<library> <objects.o>
}}}
the library will __never__ be linked, because it's not required at the
time it's checked.
And with something like that:
{{{
$ gcc -l<library> -Wl,--as-needed <objects.o>
}}}
library will allways be linked, even if it's not required.
=== Short examples ===
Most of problems are with readline/ncurses and tinfo, and it's nice
example:
tinfo is required by both readline and ncurses, and both are linked with
this library (now, when I've fixed readline).
But some packages link with readline or ncurses while they use __only__
symbols from tinfo.
''Without'' {{{--as-needed}}} those executables work because
they are linked with tinfo from readline/ncurses libraries.
''With'' {{{--as-needed}}} it
will not work, because readline/ncurses contain no symbols required
by executable
so they are not linked, it's dependencies naturally are neither linked.
So there is a need to pass {{{-ltinfo}}}. If it requires only symbols from
tinfo it's ok to {{{s/ncurses/tinfo/}}}. But if it realy requires
readline/ncurses but
there is some executable (or ./configure) which requires only tinfo both
{{{-lreadline}}}/{{{-lncurses}}} and {{{-ltinfo}}} should be passed.
----
Other common problem is when package produces some shared libraries
without linking them with all required libraries, and everything is
linked at the end to one binary. So we have:
{{{
$ gcc -Wl,--as-needed -o executable <objects.o> -l2 -l1
}}}
and normally objects require only library 2, and -l1 is required by -l2.
As I said it checks only for symbols from objects, so -l1 is not linked.
Normally it is easy to fix it, simply make sure while linking -l2 it is
linked to -l1.
== Examples ==
=== 1. unresolved symbols in executable ===
xmoto
With {{{-Wl,--as-needed}}} enabled it stops on something like this:
{{{
x86_64-pld-linux-g++ -DNOMMGR -Wall -DGAMEDATADIR=\"/usr/share/xmoto\" -ggdb -O2 -Wl,--as-needed -o xmoto-edit BuiltInFont.o [...object files...] Packager.o -lGL -lcurl -lode -llualib50 -llua50 -lSDL_mixer -lbz2 -lz -lpng -ljpeg
VApp.o: In function `vapp::App::getRealTime()':
src/VApp.cpp:287: undefined reference to `SDL_GetTicks'
VApp.o: In function `vapp::App::getTime()':
src/VApp.cpp:284: undefined reference to `SDL_GetTicks'
[... bunch of missing SDL functions ...]
Editor.o: In function `vapp::EditorApp::viewDrawGrid()':
src/Editor.cpp:777: undefined reference to `SDL_GetMouseState'
Editor.o:src/Editor.cpp:46: more undefined references to `SDL_GetMouseState' follow
EditorMain.o: In function `main':
src/EditorMain.cpp:59: undefined reference to `SDL_Quit'
collect2: ld returned 1 exit status
make[1]: *** [xmoto-edit] Error 1
}}}
So let's try to find some of missing symbols:
{{{
$ grep SDL_GetMouseState /usr/lib64/libSDL*.so
Binary file /usr/lib64/libSDL.so matches
}}}
they are in {{{-lSDL}}}, but binary does not link with {{{-lSDL}}};
edit Makefile by hand and add {{{-lSDL}}} at the same place {{{-lSDL_mixer}}} is:
{{{LIBS = -lcurl -lode -llualib50 -llua50 -lSDL_mixer -lSDL -lbz2 -lz -lpng -ljpeg}}}
What we get after running make in build tree:
{{{
x86_64-pld-linux-g++ -DNOMMGR -Wall -DGAMEDATADIR=\"/usr/share/xmoto\" -ggdb -O2 -Wl,--as-needed -o xmoto-edit BuiltInFont.o [...object files...] Packager.o -lcurl -lode -llualib50 -llua50 -lSDL_mixer -lSDL -lbz2 -lz -lpng -ljpeg
VApp.o: In function `vapp::App::grabScreen()':
src/VApp.cpp:667: undefined reference to `glReadBuffer'
src/VApp.cpp:671: undefined reference to `glReadPixels'
[...more missing gl functions...]
src/Editor.cpp:1280: undefined reference to `glEnable'
src/Editor.cpp:1288: undefined reference to `glDisable'
collect2: ld returned 1 exit status
}}}
Same story:
{{{
$ grep glEnableClientState /usr/lib64/lib*.so
Binary file /usr/lib64/libGL.so matches
}}}
{{{LIBS = -lcurl -lode -llualib50 -llua50 -lSDL_mixer -lSDL -lGL -lbz2 -lz -lpng -ljpeg}}}
But take a look at spec file, -lGL thing was fixed there already:
{{{
%{__make} \
GL_LIBS="-lGL"
}}}
Anyway, lets run make, and what we get ?
{{{
x86_64-pld-linux-g++ -DNOMMGR -Wall -DGAMEDATADIR=\"/usr/share/xmoto\" -mfpmath=sse -ggdb -O2 -ftree-vectorize -ftree-vectorizer-verbose=1 -march=athlon64 -mmmx -msse -msse2 -m3dnow -s -Wl,--as-needed -Wl,-s -o xmoto-edit BuiltInFont.o Image.o LevelSrc.o VApp.o VBezier.o VDraw.o VDrawText.o VFileIO.o VMath.o VTexture.o VXml.o tim.o tim_io_stdio.o tim_jpeg.o tim_memory_crt.o tim_png.o tinystr.o tinyxml.o tinyxmlerror.o tinyxmlparser.o md5.o md5file.o FileCompression.o SwapEndian.o DBuffer.o CRCHash.o Theme.o WWW.o Editor.o EditorMain.o EditorData.o EditorLog.o Packager.o -lcurl -lode -llualib50 -llua50 -lSDL_mixer -lSDL -lGL -lbz2 -lz -lpng -ljpeg
make[1]: Leaving directory `/home/users/sparky/rpm/BUILD/xmoto-0.2.0'
}}}
''It worked !''
===== Why was it working without --as-needed ? =====
Answer is realy easy: libSDL is required by SDL_mixer:
{{{
$ ldd /usr/lib64/libSDL_mixer-1.2.so.0.2.4 | grep SDL
libSDL-1.2.so.0 => /usr/lib64/libSDL-1.2.so.0 (0x00002ab425307000)
}}}
but xmoto-edit contains no SDL_mixer symbols, that's why xmoto-edit
wasn't linked with SDL_mixer, and nothing provided SDL library.
Can you see now why was it so stupid to disable {{{--as-needed}}} ? It worked
just perfectly disabling unneeded library !
----
Finally, fix for this may be:
{{{
%configure \
LIBS="-lSDL -lGL"
}}}
or patching configure.in
and the result is:
Wrote: /home/users/sparky/rpm/RPMS/xmoto-0.2.0-2.x86_64.rpm
=== 2. unresolved symbols in library while linking executable ===
That's the most common and a little more difficult case,
evolution-data-server:
Compilation stops at this place:
{{{
/bin/sh ../libtool --tag=CC --mode=link x86_64-pld-linux-gcc -ggdb -O2 -Wall -Wmissing-prototypes -Wno-sign-compare -Wl,--as-needed -o test-source-selector test-source-selector.o libedataserverui-1.2.la ../libedataserver/libedataserver-1.2.la -pthread -lglade-2.0 -lgtk-x11-2.0 -lxml2 -lgdk-x11-2.0 -latk-1.0 -lgdk_pixbuf-2.0 -lpangocairo-1.0 -lXext -lXrender -lXinerama -lXi -lXrandr -lXcursor -lXfixes -lcairo -lpangoft2-1.0 -lfontconfig -lfreetype -lz -lpango-1.0 -lX11 -lgnome-2 -lpopt -lbonobo-2 -lgnomevfs-2 -lbonobo-activation -lgconf-2 -lgobject-2.0 -lORBit-2 -lm -lgmodule-2.0 -ldl -lgthread-2.0 -lgnome-keyring -lglib-2.0 -lpthread
x86_64-pld-linux-gcc -ggdb -O2 -ftree-vectorize -ftree-vectorizer-verbose=1 -march=athlon64 -mmmx -msse -msse2 -m3dnow -mfpmath=sse -Wall -Wmissing-prototypes -Wno-sign-compare -Wl,--as-needed -o .libs/test-source-selector test-source-selector.o -pthread ./.libs/libedataserverui-1.2.so [many, many .so and -l libraries] -lpthread
./.libs/libedataserverui-1.2.so: undefined reference to `glade_xml_new'
./.libs/libedataserverui-1.2.so: undefined reference to `gnome_keyring_find_items_sync'
./.libs/libedataserverui-1.2.so: undefined reference to `gnome_keyring_get_default_keyring_sync'
./.libs/libedataserverui-1.2.so: undefined reference to `gnome_keyring_attribute_list_free'
./.libs/libedataserverui-1.2.so: undefined reference to `glade_xml_get_widget'
./.libs/libedataserverui-1.2.so: undefined reference to `gnome_keyring_create_sync'
./.libs/libedataserverui-1.2.so: undefined reference to `gnome_keyring_item_delete_sync'
./.libs/libedataserverui-1.2.so: undefined reference to `gnome_keyring_item_create_sync'
collect2: ld returned 1 exit status
make[2]: *** [test-source-selector] Error 1
}}}
It's different case, now it isn't problem with binary file, but with
shared library. And the difficulty is it shows up at executable-linking
time, because undefined symbols in libraries are permited.
OK, lets try to fix that library:
{{{
$ grep gnome_keyring_item_delete_sync /usr/lib64/lib*.so
Binary file /usr/lib64/libgnome-keyring.so matches
$ grep glade_xml_new /usr/lib64/lib*.so
Binary file /usr/lib64/libglade-2.0.so matches
}}}
Editing Makefile we find:
{{{GNOME_KEYRING_LIBS = -lgnome-keyring -lglib-2.0}}}
So add this one and glade to that library deps:
{{{
libedataserverui_1_2_la_LIBADD = \
$(top_builddir)/addressbook/libebook/libebook-1.2.la \
$(GNOME_KEYRING_LIBS) -lglade-2.0 \
$(E_DATA_SERVER_LIBS)
}}}
As it uses libtool, remove .la to force regeneration:
{{{$ rm libedataserverui-1.2.la}}}
and try to build
{{{$ make}}}
passes without problems.
Now we only need to fix it correcly, after looking at configure.in and
Makefile.am one can see it was only a typo:
{{{
libedataserverui_1_2_la_LIBADD = \
$(top_builddir)/addressbook/libebook/libebook-1.2.la \
$(E_DATA_SERVER_UI_LIBS)
^^^
}}}
===== Why was it working without --as-needed ? =====
test-source-selector binary was linked with all libraries needed by
libedataserverui-1.2.so, and the binary was the one who provided
missing symbols to libedataserverui-1.2.so
=== 3. ===
Two of most difficult of common problems at one, evolution.spec:
The difficulties are:
1. it appears in configure, what may be difficult to fix and difficult to find what the real problem is
2. the problem is not a missing library, but arguments order
configure stops with such message, which says nothing:
{{{
checking if pilot-link handles UTF-8 conversions... no
configure: error: evolution requires pilot-link to have working UTF-8 conversion routines
}}}
let's look at config.log:
{{{
x86_64-pld-linux-gcc -o conftest -ggdb -O2 -DORBIT2=1 -pthread -I/usr/include/libgnome-2.0 [...many -I...] -I/usr/include/libxml2 -Wl,--as-needed -pthread -lgpilotd [...many -l...] -lglib-2.0 conftest.c >&5
/home/users/sparky/tmp/ccgrL9ll.o: In function `main':
/home/users/sparky/rpm/BUILD/evolution-2.7.90/conftest.c:64: undefined reference to `convert_ToPilotChar'
collect2: ld returned 1 exit status
}}}
function '{{{convert_ToPilotChar}}}', may be found in passed library, but take
a look at section about positions, arguments order is incorrect:
libraries go before objects (conftest.c)
it's very common when someone puts {{{-l<>}}} in {{{LDFLAGS}}} instead of {{{LIBS}}},
that was the case too
just take a look at my fix:
{{{
- LDFLAGS_save="$LDFLAGS"
- LDFLAGS="$LDFLAGS $GNOME_PILOT_LIBS"
+ LIBS_save="$LIBS"
+ LIBS="$LIBS $GNOME_PILOT_LIBS"
[...]
- LDFLAGS="$LDFLAGS_save"
+ LIBS="$LIBS_save"
}}}
with this simple change everything works perfectly
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