linker: '-lpng' inhibits '-lz'

[EdouardC]

I got an error when building an executable from shared libraries, using GCC-4.7.3 provided by the linux distribution. I guess the problem is between libpng and zlib (the former uses the latter), but I don't know why. The following problem doesn't appear if I use a GCC version completely compiled by myself. Moreover, it doesn't occur on at least two other linux distros (Fedora 16 and ubuntu-10.04)
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Description: when I issue the command:
$ gfortran -o test_muesli_config_fml test_muesli_config_fml.o -fopenmp -Wl,--rpath,/usr/local/lib/muesli /usr/local/lib/muesli/libfml.so -lstdc++ -Wl,--rpath,/usr/lib /usr/lib/liblapack.so -Wl,--rpath,/usr/lib /usr/lib/libblas.so -lpng -lz -lpthread -lreadline -lhistory -Wl,--trace-symbol=gzwrite

I obtained the error:
/usr/local/lib/muesli/libfml.so: reference to gzwrite
/usr/lib/gcc/x86_64-linux-gnu/4.7/../../../x86_64-linux-gnu/libz.so: definition of gzwrite
/usr/local/lib/muesli/libfml.so: undefined reference to `gzwrite'
/usr/local/lib/muesli/libfml.so: undefined reference to `gzopen'
/usr/local/lib/muesli/libfml.so: undefined reference to `gzclose'
/usr/local/lib/muesli/libfml.so: undefined reference to `gzread'
collect2: error: ld returned 1 exit status

If I remove the -lpng option (which is actually not used), the error disappear!

In addition, a different try with another program (which USE libpng) leads to a successful build.

ProblemType: Bug
DistroRelease: Ubuntu 13.04
Package: gcc 4:4.7.3-1ubuntu10
ProcVersionSignature: Ubuntu 3.8.0-31.46-generic 3.8.13.8
Uname: Linux 3.8.0-31-generic x86_64
ApportVersion: 2.9.2-0ubuntu8.3
Architecture: amd64
Date: Wed Oct 9 10:11:16 2013
InstallationDate: Installed on 2012-11-07 (335 days ago)
InstallationMedia: Ubuntu 12.10 "Quantal Quetzal" - Release amd64 (20121017.5)
MarkForUpload: True
SourcePackage: gcc-defaults
UpgradeStatus: Upgraded to raring on 2013-05-12 (149 days ago)

[Matthias Klose (doko)]

This is an error in how your local libfml.so is linked. make sure that it is linked against libz.

[EdouardC (edouard-canot)]

Many thanks.

É. C.

--
Édouard Canot
IRISA/CNRS
[phone]
http://people.irisa.fr/Edouard.Canot