It is a gcc bug which has been fixed in CVS.

*** This bug has been marked as a duplicate of 1025 ***

BTW, the linker bug is also fixed in CVS.

Reopen.

The problem is caused by

#pragma GCC visibility push(hidden)

which needs support from glibc and libstdc++ as well as gcc. My modified gcc
4.0 gave:

/usr/gcc-4.0/bin/g++ -m32 -O3 -fPIC -c -o net_error.o net_error.ii
/usr/gcc-4.0/bin/g++ -m32 -fPIC -shared -o net_error.so net_error.o
net_error.o(.text+0x50): In function `boost::network::net_error::net_error()':
net_error.cpp: undefined reference to `__errno_location'
net_error.o(.text+0x5f):net_error.cpp: undefined reference to `strerror'
net_error.o(.text+0x72):net_error.cpp: undefined reference to
`std::basic_string<char, std::char_traits<char>, std::allocator<char>
>::basic_string(char const*, std::allocator<char> const&)'
net_error.o(.text+0x81):net_error.cpp: undefined reference to
`std::runtime_error::runtime_error(std::string const&)'
net_error.o(.text+0x96):net_error.cpp: undefined reference to
`std::string::_Rep::_S_empty_rep_storage'
net_error.o(.text+0x22e):net_error.cpp: undefined reference to
`__gnu_cxx::__exchange_and_add(int volatile*, int)'
net_error.o(.text+0x245):net_error.cpp: undefined reference to
`std::string::_Rep::_M_destroy(std::allocator<char> const&)'
net_error.o(.text+0x25d):net_error.cpp: undefined reference to
`std::string::_Rep::_S_empty_rep_storage'
net_error.o(.text+0x286):net_error.cpp: undefined reference to
`__gnu_cxx::__exchange_and_add(int volatile*, int)'
net_error.o(.text+0x299):net_error.cpp: undefined reference to
`std::string::_Rep::_M_destroy(std::allocator<char> const&)'
net_error.o(.text+0x380): In function `boost::network::net_error::net_error()':
net_error.cpp: undefined reference to `__errno_location'
net_error.o(.text+0x38f):net_error.cpp: undefined reference to `strerror'
net_error.o(.text+0x3a2):net_error.cpp: undefined reference to
`std::basic_string<char, std::char_traits<char>, std::allocator<char>
>::basic_string(char const*, std::allocator<char> const&)'
net_error.o(.text+0x3b1):net_error.cpp: undefined reference to
`std::runtime_error::runtime_error(std::string const&)'
net_error.o(.text+0x3c6):net_error.cpp: undefined reference to
`std::string::_Rep::_S_empty_rep_storage'
net_error.o(.text+0x55e):net_error.cpp: undefined reference to
`__gnu_cxx::__exchange_and_add(int volatile*, int)'
net_error.o(.text+0x575):net_error.cpp: undefined reference to
`std::string::_Rep::_M_destroy(std::allocator<char> const&)'
net_error.o(.text+0x58d):net_error.cpp: undefined reference to
`std::string::_Rep::_S_empty_rep_storage'
net_error.o(.text+0x5b6):net_error.cpp: undefined reference to
`__gnu_cxx::__exchange_and_add(int volatile*, int)'
net_error.o(.text+0x5c9):net_error.cpp: undefined reference to
`std::string::_Rep::_M_destroy(std::allocator<char> const&)'
net_error.o(.gnu.linkonce.d._ZTVN5boost7network9net_errorE[_ZTVN5boost7network9net_errorE]+0x10):
undefined reference to `std::runtime_error::what() const'
net_error.o(.gnu.linkonce.d._ZTIN5boost7network9net_errorE[_ZTIN5boost7network9net_errorE]+0x0):
undefined reference to `vtable for __cxxabiv1::__si_class_type_info'
net_error.o(.gnu.linkonce.d._ZTIN5boost7network9net_errorE[_ZTIN5boost7network9net_errorE]+0x8):
undefined reference to `typeinfo for std::runtime_error'
net_error.o(.gnu.linkonce.t._ZN5boost7network9net_errorD1Ev[_ZN5boost7network9net_errorD1Ev]+0x21):
In function `boost::network::net_error::~net_error()':
net_error.cpp: undefined reference to `std::runtime_error::~runtime_error()'
net_error.o(.gnu.linkonce.t._ZN5boost7network9net_errorD0Ev[_ZN5boost7network9net_errorD0Ev]+0x26):
In function `boost::network::net_error::~net_error()':
net_error.cpp: undefined reference to `std::runtime_error::~runtime_error()'
net_error.o(.gnu.linkonce.t._ZN9__gnu_cxx20__common_pool_policyINS_6__poolELb1EE21_S_destroy_thread_keyEPv[_ZN9__gnu_cxx20__common_pool_policyINS_6__poolELb1EE21_S_destroy_thread_keyEPv]+0x37):
In function `__gnu_cxx::__common_pool_policy<__gnu_cxx::__pool,
true>::_S_destroy_thread_key(void*)':
net_error.cpp: undefined reference to
`__gnu_cxx::__pool<true>::_M_destroy_thread_key(void*)'
net_error.o(.gnu.linkonce.t._ZN9__gnu_cxx20__common_pool_policyINS_6__poolELb1EE21_S_destroy_thread_keyEPv[_ZN9__gnu_cxx20__common_pool_policyINS_6__poolELb1EE21_S_destroy_thread_keyEPv]+0xf5):net_error.cpp:
undefined reference to `__gnu_cxx::__pool<true>::_M_destroy_thread_key(void*)'
net_error.o(.gnu.linkonce.t._ZN9__gnu_cxx20__common_pool_policyINS_6__poolELb1EE13_S_initializeEv[_ZN9__gnu_cxx20__common_pool_policyINS_6__poolELb1EE13_S_initializeEv]+0x3a):
In function `__gnu_cxx::__common_pool_policy<__gnu_cxx::__pool,
true>::_S_initialize()':
net_error.cpp: undefined reference to
`__gnu_cxx::__pool<true>::_M_initialize(void (*)(void*))'
net_error.o(.gnu.linkonce.t._ZN9__gnu_cxx20__common_pool_policyINS_6__poolELb1EE13_S_initializeEv[_ZN9__gnu_cxx20__common_pool_policyINS_6__poolELb1EE13_S_initializeEv]+0xfb):net_error.cpp:
undefined reference to `__gnu_cxx::__pool<true>::_M_initialize(void (*)(void*))'
/usr/bin/ld: net_error.so: hidden symbol `strerror' isn't defined
/usr/bin/ld: final link failed: Nonrepresentable section on output
collect2: ld returned 1 exit status

Fixed. Now I get

gcc -fPIC -O2 -g   -c -o foo.o foo.c
gcc -shared -o libfoo.so foo.o
gcc -fPIC -O2 -g   -c -o x.o x.c
gcc -shared -o libx.so x.o
gcc -fPIC -O2 -g   -c -o y.o y.c
gcc -o y1 y.o x.o libfoo.so -Wl,-rpath,.
/usr/local/bin/ld: x.o(.text+0x11): unresolvable R_386_GOTOFF relocation against
symbol `foo'
/usr/local/bin/ld: final link failed: Nonrepresentable section on output
collect2: ld returned 1 exit status
make: *** [y1] Error 1