[tor-bugs] #6622 [Tor Relay]: Tor link against static zlib broken by -pie switch

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#6622: Tor link against static zlib broken by -pie switch
-------------------------+--------------------------------------------------
 Reporter:  tmpname0901  |          Owner:                    
     Type:  defect       |         Status:  new               
 Priority:  major        |      Milestone:  Tor: 0.2.3.x-final
Component:  Tor Relay    |        Version:  Tor: 0.2.3.20-rc  
 Keywords:               |         Parent:                    
   Points:               |   Actualpoints:                    
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 Build environment: CentOS v5.8/x86_64 with GCC v4.4.6.

 I'm linking Tor against staticly-built versions of zlib (v1.2.7) and
 OpenSSL (v1.0.1c).  This has always worked correctly with the 0.2.2.x
 versions of Tor.  With version 0.2.3-20-rc the final link fails with this
 error:

 $ gcc44 -m64 -O2 -g -march=native -mno-avx -D_FORTIFY_SOURCE=2 -fstack-
 protector-all -Wstack-protector -fwrapv --param ssp-buffer-size=1 -fPIE
 -Wall -fno-strict-aliasing
 -L/home/rpmbuild/BUILD/tor-0.2.3.20-rc/dependencies/lib -pie -z relro -z
 now -o tor tor_main.o ./libtor.a ../common/libor.a ../common/libor-
 crypto.a ../common/libor-event.a
 /home/rpmbuild/BUILD/tor-0.2.3.20-rc/dependencies/lib/libz.a -lm
 /home/rpmbuild/BUILD/tor-0.2.3.20-rc/dependencies/lib/libevent.a
 /home/rpmbuild/BUILD/tor-0.2.3.20-rc/dependencies/lib/libssl.a
 /home/rpmbuild/BUILD/tor-0.2.3.20-rc/dependencies/lib/libcrypto.a
 /home/rpmbuild/BUILD/tor-0.2.3.20-rc/dependencies/lib/libz.a -ldl -lrt
 /usr/bin/ld:
 /home/rpmbuild/BUILD/tor-0.2.3.20-rc/dependencies/lib/libz.a(deflate.o):
 relocation R_X86_64_32S against `_length_code' can not be used when making
 a shared object; recompile with -fPIC
 /home/rpmbuild/BUILD/tor-0.2.3.20-rc/dependencies/lib/libz.a: could not
 read symbols: Bad value

 Removing that -pie switch allows the link to complete successfully.

 The GCC doc suggests that the linking error is due to not having used -pie
 during compilation.  This seems to be true as neither zlib nor openssl nor
 libevent are compiled with this switch (or with -fPIC).  Not even the Tor
 source is compiled with -pie.  It is used nowhere until that final link.

 The offending symbol is defined in zlib's deflate.c, which is compiled
 with this command line:

 gcc44 -m64 -O2 -g -march=native -mno-avx -c -o deflate.o deflate.c

 Do we really need this -pie switch when linking Tor?  What is the adverse
 impact if I just remove it from the linker input?

-- 
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/6622>
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