What can create a lexical error in C?

Question

Besides not closing a comment /*..., what constitutes a lexical error in C?

Answer 1

Here are some:

 "abc

where EOF is the end of the file. In fact, EOF in the middle of many lexemes should produce errors:

 0x

I assume that using bad escapes in strings is illegal:

  "ab\qcd"

Probably trouble with floating point exponents

 1e+%

Arguably, you shouldn't have stuff at the end of a preprocessor directive:

#if x   %