This is a different error from the one previously reported. Using the 'samples/cpp_tokens' example preprocessor with the input file: #define __glibcpp_function_requires(...) give the following error message test.C(1): error: ill formed #define directive: __glibcpp_function_requires This error was found when preprocessing the file: #include <algorithm> where the implementation of algorithm is from gcc. The error from the custom preprocessor is: PATH_TO_GCC_STL_IMPLEMENTATION/bits/concept_check.h(52): error: ill formed #define directive: __glibcpp_function_requires It is important for us to be able to preprocess this header file since we aim for gcc compatibility. Is this standard preprocessor syntax? Could Wave support this syntax? Regards Andreas