armv6 issues

I need to change compiler from arm7 to armv6.
When I add -march=armv6 to miscellaneous as option I get the following 
error:
Here is a part of the output, full output can be posted if it helps to 
solve this.

                from ../src/ZERO_RPI.cpp:9:
/usr/arm-linux-gnueabihf/include/c++/5/exception: In constructor 
‘std::exception::exception()’:
/usr/arm-linux-gnueabihf/include/c++/5/exception:63:39: sorry, 
unimplemented: Thumb-1 hard-float VFP ABI
     exception() _GLIBCXX_USE_NOEXCEPT { }
                                       ^
make: *** [src/ZERO_RPI.o] Error 1
src/subdir.mk:18: recipe for target 'src/ZERO_RPI.o' failed


I can “fix” the  error by adding -marm  to the options.

The C++ code then compiles but does not run properly.
1. What does Thumb do?
2. Do I have to add it to compiler with armv6 addition and how?
3. Am I missing some other option to make the compiler happy and make 
the code run ?


Any help will be appreciated