coss/store_io_coss.cc: In member function 'virtual StoreIOState::Pointer CossSwapDir::createStoreIO(StoreEntry&, void (*)(void*, int, StoreIOState::Pointer), void (*)(void*, int, StoreIOState::Pointer), void*)':
coss/store_io_coss.cc:151:133: error: declaration of 'callback' shadows a member of 'this' [-Werror=shadow]
coss/store_io_coss.cc: In member function 'virtual StoreIOState::Pointer CossSwapDir:penStoreIO(StoreEntry&, void (*)(void*, int, StoreIOState::Pointer), void (*)(void*, int, StoreIOState::Pointer), void*)':
coss/store_io_coss.cc:201:78: error: declaration of 'callback' shadows a member of 'this' [-Werror=shadow]
coss/store_io_coss.cc: In member function 'virtual void CossState::read_(char*, size_t, off_t, void (*)(void*, const char*, ssize_t, StoreIOState::Pointer), void*)':
coss/store_io_coss.cc:299:93: error: declaration of 'callback_data' shadows a member of 'this' [-Werror=shadow]
coss/store_io_coss.cc:299:93: error: declaration of 'callback' shadows a member of 'this' [-Werror=shadow]
coss/store_io_coss.cc:299:93: error: declaration of 'offset' shadows a member of 'this' [-Werror=shadow]
coss/store_io_coss.cc:302:18: error: declaration of 'SD' shadows a member of 'this' [-Werror=shadow]
coss/store_io_coss.cc: In member function 'virtual void CossState::write(const char*, size_t, off_t, void (*)(void*))':
coss/store_io_coss.cc:338:78: error: declaration of 'offset' shadows a member of 'this' [-Werror=shadow]
coss/store_io_coss.cc:353:18: error: declaration of 'SD' shadows a member of 'this' [-Werror=shadow]
coss/store_io_coss.cc: In member function 'void CossState::doCallback(int)':
coss/store_io_coss.cc:404:13: error: declaration of 'callback' shadows a member of 'this' [-Werror=shadow]
coss/store_io_coss.cc: In member function 'void CossMemBuf::maybeWrite(CossSwapDir*)':
coss/store_io_coss.cc:499:40: error: declaration of 'SD' shadows a member of 'this' [-Werror=shadow]
coss/store_io_coss.cc: In member function 'void CossMemBuf::write(CossSwapDir*)':
coss/store_io_coss.cc:514:35: error: declaration of 'SD' shadows a member of 'this' [-Werror=shadow]
cc1plus: all warnings being treated as errors
make[3]: *** [store_io_coss.lo] Error 1
make[3]: Leaving directory `/root/squid-3.4.7/src/fs'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/root/squid-3.4.7/src'
make[1]: *** [all] Error 2
make[1]: Leaving directory `/root/squid-3.4.7/src'
make: *** [all-recursive] Error 1

...and are we supposed to guess as to what you're asking??? You've posted part of a compile error, but don't tell us what version/distro of Linux this is for, what you did to GET this message, where you downloaded the source, what version(s) of things you're running, or provide ANY details at all.

Provide details and ask a clear question.