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GCC 11 ICEs on all -fdirectives-only preprocessing when the files don't end with a newline. The problem is in the assertion, for empty TUs buffer->cur == buffer->rlimit and so buffer->rlimit[-1] access triggers UB in the preprocessor, for non-empty TUs it refers to the last character in the file, which can be anything. The preprocessor adds a '\n' character (or '\r', in particular if the user file ends with '\r' then it adds another '\r' rather than '\n'), but that is added after the limit, i.e. at buffer->rlimit[0]. Now, if the routine handles occassional bumping of pos to buffer->rlimit + 1, I think it is just the assert that needs changing, usually we read from *pos if pos < limit and then e.g. if it is '\r', look at the following character (which could be one of those '\n' or '\r' at buffer->rlimit[0]). There is also the case where for '\\' before the limit we read following character and if it is '\n', do one thing, if it is '\r' read another character. But in that case if '\\' was the last char in the TU, the limit char will be '\n', so we are ok. 2021-02-03 Jakub Jelinek <jakub@redhat.com> PR preprocessor/98882 * lex.c (cpp_directive_only_process): Don't assert that rlimit[-1] is a newline, instead assert that rlimit[0] is either newline or carriage return. When seeing '\\' followed by '\r', check limit before accessing pos[1]. * gcc.dg/cpp/pr98882.c: New test.