User Tools
developingpld:advanceddeveloping:fixingasneeded
Differences
This shows you the differences between two versions of the page.
| Both sides previous revision Previous revision Next revision | Previous revision | ||
|
developingpld:advanceddeveloping:fixingasneeded [2006-08-07 02:53] SamChi |
developingpld:advanceddeveloping:fixingasneeded [2007-05-27 20:51] (current) arekm |
||
|---|---|---|---|
| Line 4: | Line 4: | ||
| - | ==== Quick Workaround ==== | + | ===== Quick and ugly workaround (DON'T USE IT!) ===== |
| - | Put in spec file this line: | + | Put this line in ''spec'' file: |
| - | <file>%devine filterout_ld -Wl,--as-needed | ||
| - | </file> | ||
| - | But **don't use it** unless you really 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. | + | |
| + | <file>%define filterout_ld -Wl,--as-needed | ||
| + | </file> | ||
| + | But **don't use it** unless you really need to quickly build a package. Never ever try to commit such a change. It might be tempting to do so but if you think about it ''--as-needed'' did it's job well and disabled unneeded libraries. If building fails, it's the package that needs to get fixed, not the linker flags. | ||
| ===== How --as-needed works ===== | ===== How --as-needed works ===== | ||
| - | With ''--as-needed'' enabled only libraries which contain symbols required by __object files__ are linked. | + | With ''--as-needed'' enabled, only libraries containing symbols required by __object files__ are linked. |
| + | |||
| + | |||
| + | |||
| + | ==== Why it fails for some packages ==== | ||
| + | In other words, if you list 10 libraries and only 3 of them contain referenced symbols, others are silently discarded. This is a good thing but unfortunately some projects fail to list all their dependencies properly. | ||
| + | |||
| + | This normally works because if project requires libraries //A// and //B// and //A// itself lists //B// as a dependency, both //A// and //B// get pulled in even if the project itself only lists //A//. | ||
| + | |||
| + | Now assume that //A// is a superfluous (unneeded) dependency which gets dropped (or //A// requiring //B// is superfluous and //B// gets dropped from //A//). The symbols are no longer available. | ||
| - | == About positions == | + | ==== About positions ==== |
| - | Linker options are positional, and position is very important. Because it looks for missing symbols only in libraries coming after object file. | + | Linker options are positional, and position is very important. It looks for missing symbols only in libraries coming after object file. |
| - | Correct ones are: | + | Correct positions are: |
| <file>$ gcc $(LDFLAGS) -o $@ $(OBJECTS) $(LIBS) | <file>$ gcc $(LDFLAGS) -o $@ $(OBJECTS) $(LIBS) | ||
| Line 41: | Line 50: | ||
| <file>$ gcc -l<library> -Wl,--as-needed <objects.o> | <file>$ gcc -l<library> -Wl,--as-needed <objects.o> | ||
| </file> | </file> | ||
| - | library will allways be linked, even if it's not required. | + | library will __allways__ be linked, even if it isn't required. |
| ==== Short examples ==== | ==== 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 [[http://cvs.pld-linux.org/cgi-bin/cvsweb/SOURCES/readline-shared.patch?r1=1.6&r2=1.7|fixed readline]];). | + | 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 [[http://cvs.pld-linux.org/cgi-bin/cvsweb/SOURCES/readline-shared.patch?r1=1.6&r2=1.7|fixed readline]] is fixed). |
| - | 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 library. //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. Thats why there is a need to pass ''-ltinfo''. If it requires only symbols from tinfo it's ok to ''s/ncurses/tinfo/''. But if it really requires readline/ncurses but there is some executable (or ./configure) which requires only tinfo both ''-lreadline''/''-lncurses'' and ''-ltinfo'' should be passed. | + | 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 library. //With// ''--as-needed'' linking will not work, because readline/ncurses contain no symbols required by executable so they are not linked, it's dependencies naturally are neither linked. Thats why there is a need to pass ''-ltinfo''. If it requires only symbols from tinfo it's ok to ''s/ncurses/tinfo/''. But if it really requires readline/ncurses but there is some executable (or ./configure) which requires only tinfo both ''-lreadline''/''-lncurses'' and ''-ltinfo'' should be passed. |
| For a longer example take a look at real example nr. 1. | For a longer example take a look at real example nr. 1. | ||
| Line 61: | Line 70: | ||
| <file>$ gcc -Wl,--as-needed -o executable <objects.o> -l2 -l1 | <file>$ gcc -Wl,--as-needed -o executable <objects.o> -l2 -l1 | ||
| </file> | </file> | ||
| - | it's usual when object files require only library 2, and -l1 is required by -l2. As I said linker only checks 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 (take a look at the second real example). | + | It's usual situation when object files require only library 2, and //-l1// is required by //-l2//. As I said linker only checks 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// (take a look at the second real example). |
| Line 75: | Line 84: | ||
| - | <file>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 | + | <file>g++ -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()': | VApp.o: In function `vapp::App::getRealTime()': | ||
| Line 100: | Line 109: | ||
| Binary file /usr/lib64/libSDL.so matches | Binary file /usr/lib64/libSDL.so matches | ||
| </file> | </file> | ||
| - | 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'' | + | 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: | What we get after running make in build tree: | ||
| Line 106: | Line 115: | ||
| - | <file>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 | + | <file>g++ -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()': | VApp.o: In function `vapp::App::grabScreen()': | ||
| Line 139: | Line 148: | ||
| - | <file>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 -lGL -lbz2 -lz -lpng -ljpeg | + | <file>g++ -Wl,--as-needed -o xmoto-edit BuiltInFont.o [...object files...] 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' | make[1]: Leaving directory `/home/users/sparky/rpm/BUILD/xmoto-0.2.0' | ||
| </file> | </file> | ||
| - | //It worked !// | + | **It worked !** |
| Line 180: | Line 189: | ||
| - | <file>/bin/sh ../libtool --tag=CC --mode=link x86_64-pld-linux-gcc -ggdb -O2 -Wall -Wl,--as-needed -o test-source-selector test-source-selector.o libedataserverui-1.2.la ../libedataserver/libedataserver-1.2.la -pthread -lglade-2.0 [...many -l libraries...] | + | <file>/bin/sh ../libtool --tag=CC --mode=link gcc -Wl,--as-needed -o test-source-selector test-source-selector.o libedataserverui-1.2.la ../libedataserver/libedataserver-1.2.la -pthread -lglade-2.0 [...many -l libraries...] |
| -lgnome-keyring -lpthread | -lgnome-keyring -lpthread | ||
| - | x86_64-pld-linux-gcc -ggdb -O2 -Wall -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 | + | gcc -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 `glade_xml_new' | ||
| Line 212: | Line 221: | ||
| ''GNOME_KEYRING_LIBS = -lgnome-keyring -lglib-2.0'' | ''GNOME_KEYRING_LIBS = -lgnome-keyring -lglib-2.0'' | ||
| - | So add this one and glade to that library deps: | + | So add this one and ''-lglade-2.0'' to that library deps: |
| Line 235: | Line 244: | ||
| == Why was it working without --as-needed ? == | == 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 | + | ''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 |
| + | |||
| + | |||
| + | |||
| + | === What if broken library comes from other package ? === | ||
| + | You can check manually does library has all required symbols, simply running ' gcc //library// ', like this: | ||
| + | |||
| + | This is an example of correctly linked library: | ||
| + | |||
| + | <file>$ gcc /usr/lib64/liblftp-tasks.so.0.0.0 | ||
| + | /usr/lib64/gcc/x86_64-pld-linux/4.1.2/../../../../lib64/crt1.o: In function `_start': | ||
| + | (.text+0x20): undefined reference to `main' | ||
| + | collect2: ld returned 1 exit status | ||
| + | </file> | ||
| + | And incorrectly linked one: | ||
| + | |||
| + | <file>$ gcc /usr/lib64/liblftp-jobs.so.0.0.0 | ||
| + | /usr/lib64/gcc/x86_64-pld-linux/4.1.2/../../../../lib64/crt1.o: In function `_start': | ||
| + | (.text+0x20): undefined reference to `main' | ||
| + | /usr/lib64/liblftp-jobs.so.0.0.0: undefined reference to `StringSet::Remove(int)' | ||
| + | /usr/lib64/liblftp-jobs.so.0.0.0: undefined reference to `Buffer::Format(char const*, ...)' | ||
| + | [...] | ||
| + | /usr/lib64/liblftp-jobs.so.0.0.0: undefined reference to `SMTask::SuspendSlave()' | ||
| + | collect2: ld returned 1 exit status | ||
| + | </file> | ||
| + | **Warning:** some libraries may require to have unresolved symbols. | ||
| Line 258: | Line 292: | ||
| - | <file>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 | + | <file>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/tmp/ccgrL9ll.o: In function `main': | ||
| Line 265: | Line 299: | ||
| collect2: ld returned 1 exit status | collect2: ld returned 1 exit status | ||
| </file> | </file> | ||
| - | 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 | + | 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: | + | Just take a look at my fix: |
| Line 279: | Line 313: | ||
| + LIBS="$LIBS_save" | + LIBS="$LIBS_save" | ||
| </file> | </file> | ||
| - | with this simple change everything works perfectly. | + | With this simple change everything works perfectly. |
developingpld/advanceddeveloping/fixingasneeded.1154912017.txt.gz · Last modified: 2006-08-07 02:53 by SamChi
Page Tools
Except where otherwise noted, content on this wiki is licensed under the following license: Public Domain
