You can implemement reasonably C-like languages (eg. Objective C and various C-derived DSLs in many Lisp implementations) by a simple text transforming preproce

You can implemement reasonably C-like languages (eg. Objective C and various C-derived DSLs in many Lisp implementations) by a simple text transforming preprocessor and get reasonable error messages from the C backend (#file is your friend for achieving that). But for anything more complex you are better off implementing complete parser with your own error handling and reporting. Edit: one of the clearest signs of language implemented in this way is use of '@' character as part of syntax extensions as it is the only printable ascii character that has no syntactic meaning in C (the other such "unused character" is '$', but its meaning is implementation-defined, for example gcc has option that causes it to be accepted as part of identifiers, which is quite obviously the default on VMS)