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Linux linker: '-lpng' inhibits '-lz'?

On ubuntu-13.04, I got an error when creating an executable from shared libraries using GCC-4.7.3 provided by the linux distribution.

I think the problem is between libpng and zlib (the former uses the latter), but I don't know why.

Firstly, my team:

$ 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

which gives the following error:

/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

But notice that is -lzpresent. After that, I added the linker option --trace-symbol=to get more information:

$ 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

which, in turn, gives the results:

/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

therefore gzwritelocated in libz.so, but the linker does not use it!

By chance, I decided to remove the parameter -lpng(in fact, the libpng library is not used), and my problem is solved! Why?

-, GCC-4.7.3 ( - ), , -lpng -lz!

?

, ( USE libpng) .

2013-10-08

, ubuntu-13.04: Linux (Fedora 16 - Ubuntu-10.04), , .

ubuntu. .

2013-10-09

https://bugs.launchpad.net/ubuntu/+source/gcc-defaults/+bug/1237270

+4
1

( ubuntu ):

  • libpng.a libz.a ( , ).

  • libpng libz.a .

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