what means is defined in DSO /lib64/libz.so.1

[Sérgio Basto]

Hi , I found this error 

/usr/bin/ld: /usr/lib/gcc/x86_64-redhat-linux/4.7.0/../../../../lib64/libgpac_static.a(base_encoding.o): undefined reference to symbol 'deflate'                                                              
/usr/bin/ld: note: 'deflate' is defined in DSO /lib64/libz.so.1 so try
adding it to the linker command
line                                                                                                   
/lib64/libz.so.1: could not read symbols: Invalid
operation                                            
collect2: error: ld returned 1 exit status


Could someone help me , to understand what happens ? 

Thanks in advance, 
-- 
Sérgio M. B.