>I have to disagree about implicit functions not being a part of C anymore. I've yet to see one generate an error;
This is not really a debatable matter. There's an international standard for what is, and what is not a part of the C language.
Errors as you seem to understand them are optional for everything else except for the #error preprocessor directive. For all the other invalid C programs, only a diagnostic (like the warning you got) is required, and a conforming implementation is free to complete translating the invalid translation unit. I don't see why that would be an issue, as it's very easy to switch those warnings into translation errors if wanted.
This is not really a debatable matter. There's an international standard for what is, and what is not a part of the C language.
Errors as you seem to understand them are optional for everything else except for the #error preprocessor directive. For all the other invalid C programs, only a diagnostic (like the warning you got) is required, and a conforming implementation is free to complete translating the invalid translation unit. I don't see why that would be an issue, as it's very easy to switch those warnings into translation errors if wanted.