This probably doesn't belong to boost mailing list, but since boost has a lot of support in preprocessor, there may be someone who can answer my question. I'm using general 'C' compiler in this project (hence I cannot use boost headers). I want to write a macro as follows; #define ERR(x, y) \ { \ # ifndef ERR##x \ # define ERR##x \ # else \ # error ERR##x already defined\ # endif y = x; \ } When I compile, I get the error saying, error C2162: expected macro formal parameter on all the preprocessor lines inside the #define ERR(...) body. The reason I want to do something like this is to have some unique numbers in the code (like locators. Don't want to use __FILE__ and __LINE__ for security reasons) and want to capture duplicates at compiletime. For example if I say in the code, int err = 10000 in one file, I don't want any other engineer to use 10000 in the anywhere else in the code. So I started writing something like int err = ERR(10000) but got into several compiler problems as I mentioned above. Any suggeations? Thanks, --Suman