How do you disable the unused variable warnings coming out of gcc in 3rd party code I do not wish to edit?

Question

I'd like to know what switch you pass to the gcc compiler to turn off unused variable warnings? I'm getting errors out of boost on windows and I do not want to touch the boost code:

C:\boost_1_52_0/boost/system/error_code.hpp: At global scope:
C:\boost_1_52_0/boost/system/error_code.hpp:214:36: error: 'boost::system::posix_category' defined but not used [-Werror=unused-variable]
C:\boost_1_52_0/boost/system/error_code.hpp:215:36: error: 'boost::system::errno_ecat' defined but not used [-Werror=unused-variable]
C:\boost_1_52_0/boost/system/error_code.hpp:216:36: error: 'boost::system::native_ecat' defined but not used [-Werror=unused-variable]

I tried using both -Wunused-value and -Wno-unused-value but neither suppressed the messages above.

What is the right command, here is my compile line:

g++  -g -fno-inline -Wall -Werror -Wextra -Wfloat-equal -Wshadow
-Wpointer-arith -Wcast-qual -Wcast-align -Wwrite-strings -Wno-conversion 
-Wdisabled-optimization -Wredundant-decls -Wunused-value -Wno-deprecated 
-IC:\\boost_1_52_0 -D_LARGEFILE_SOURCE -D_LARGEFILE64_SOURCE -D_FILE_OFFSET_BITS=64 
-c -o op.o op.cpp

Perhaps the -Wall overrides my goal?

Answer 1

The -Wno-unused-variable switch usually does the trick. However, that is a very useful warning indeed if you care about these things in your project. It becomes annoying when GCC starts to warn you about things not in your code though.

I would recommend you keeping the warning on, but use -isystem instead of -I for include directories of third-party projects. That flag tells GCC not to warn you about the stuff you have no control over.

For example, instead of -IC:\\boost_1_52_0, say -isystem C:\\boost_1_52_0.

Hope it helps. Good Luck!