Is there a way you can make this change additive instead of mutative? It may break integration with some other tools.

I may need to consider improving the mechanism for customizing the error format.

Actually, after my change, the error format has become compliant to that of GCC. GCC error messages are written to stderr and has both line number and column number separated by colon. http://gcc.gnu.org/onlinedocs/gcc-4.7.3/gnat_ugn_unw/Output-and-Error-Message-Control.html . I guess, clang also follows this format.

Since GCC can be considered as the standard compiler on Linux/Mac, and all tools and IDEs on these platforms are expected to parse the error messages from gcc, I believe my change should not break any existing tools on these platforms. And, if this change is going to break any tool, that tool is already broken, as it cannot parse even the GCC error messages.

However, I am open for discussion. Do you have any suggestion?

Nope, sounds good to me.