Bug 888285 - order of libraries linkedc to
Summary: order of libraries linkedc to
Alias: None
Product: Fedora
Classification: Fedora
Component: binutils
Version: 17
Hardware: Unspecified
OS: Unspecified
Target Milestone: ---
Assignee: Nick Clifton
QA Contact: Fedora Extras Quality Assurance
Depends On:
TreeView+ depends on / blocked
Reported: 2012-12-18 13:01 UTC by Ales Kozumplik
Modified: 2014-09-30 23:40 UTC (History)
4 users (show)

Fixed In Version:
Doc Type: Bug Fix
Doc Text:
Clone Of:
Last Closed: 2013-08-01 05:39:26 UTC
Type: Bug

Attachments (Terms of Use)

Description Ales Kozumplik 2012-12-18 13:01:39 UTC
Description of problem:

I am seeing a strange behavior of gcc when compiling the latest version of libsolv:

/usr/bin/gcc   -Wall -Wl,--as-needed    CMakeFiles/deltainfoxml2solv.dir/deltainfoxml2solv.o  -o deltainfoxml2solv -rdynamic libtoolstuff.a ../ext/libsolvext.so.0 ../src/libsolv.so.0 -ldb -lrpmio -lrpm -lexpat -lz -Wl,-rpath,/home/akozumpl/libsolv/build/ext:/home/akozumpl/libsolv/build/src: 
../ext/libsolvext.so.0: undefined reference to `gzclose'
../ext/libsolvext.so.0: undefined reference to `gzdopen'
../ext/libsolvext.so.0: undefined reference to `gzopen64'
../ext/libsolvext.so.0: undefined reference to `gzread'
../ext/libsolvext.so.0: undefined reference to `gzwrite'

There is a source in libsolvext.so that uses the mentioned zlib functions. However, notice that -lz is the last library on the command line and so ld should in any case be able to pick up any unresolved references from there, as stated by 'man ld': "If the archive defines a symbol which was undefined in some object which appeared before the archive on the command line, the linker will include the appropriate file(s) from the archive. "

If I move -lz forward on the command line, the linking passes fine:
/usr/bin/gcc   -Wall -Wl,--as-needed    CMakeFiles/deltainfoxml2solv.dir/deltainfoxml2solv.o  -o deltainfoxml2solv -rdynamic libtoolstuff.a ../ext/libsolvext.so.0 ../src/libsolv.so.0 -ldb -lz -lrpmio -lrpm -lexpat -Wl,-rpath,/bhome/akozumpl/libsolv/build/ext:/home/akozumpl/libsolv/build/src: 

gcc --version
gcc (GCC) 4.7.0 20120507 (Red Hat 4.7.0-5)

Comment 1 Ales Kozumplik 2012-12-18 14:54:17 UTC
Also see: https://github.com/openSUSE/libsolv/pull/22#issuecomment-11489652

Comment 2 Jakub Jelinek 2012-12-18 14:57:30 UTC
First of all, this has nothing to do with gcc.
I think --as-needed only adds libraries that are needed by the binary or library being linked, not for any libraries that were incorrectly linked before (from the above it looks like libsolvext.so.0 should have been linked against -lz when it uses it).

Comment 3 Ales Kozumplik 2012-12-19 14:55:00 UTC
Thanks Jakub, you actually pointed us in the right direction: libsolvext.so should had already been linked against zlib but it was not. 

I wonder maybe 'ld' should scream when linking libsolvext.so then as it is clearly missing a dependency then. Also, the original problem still stands: combination of a missing shared dependency and using --as-needed can produce different results depending on the exact order of libraries being linked to the final binary.

Comment 4 Fedora End Of Life 2013-07-04 01:19:53 UTC
This message is a reminder that Fedora 17 is nearing its end of life.
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Comment 5 Fedora End Of Life 2013-08-01 05:39:31 UTC
Fedora 17 changed to end-of-life (EOL) status on 2013-07-30. Fedora 17 is 
no longer maintained, which means that it will not receive any further 
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