How to prevent `#warning` messages from being treated as an error?

Question

I'm trying to compile introduce the -Werror flag in an existing codebase. One of the issues I'm encountering is that at some places #warning is used to display informational messages. These should not be treated as an error.

One solution would be to use #pragma message instead, but this does not seem to be supported by older versions of gcc. (Our build servers use gcc 4.1.2).

Can anyone help me fix this?

Answer 1

In gcc-4.6 and above, you can use -Wno-error=cpp. In at least the clang released with Lion and later, you can use -Wno-error=#warnings. But since your build servers use an ancient gcc, you're probably out of luck there.

In general, pass -fdiagnostics-show-option to have warnings show output like:

test.cc:1:2: warning: #warning hello [-Wcpp]

which tells you a warning flag that controls the warning. In gcc >=4.6 and clang, this is the default, so knowing to pass it may not be too useful anymore.