[Bug c/67266] New: Use of "cpp -P ..." collapses multiple blank lines

["mike at flyn dot org" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67266

            Bug ID: 67266
           Summary: Use of "cpp -P ..." collapses multiple blank lines
           Product: gcc
           Version: 5.1.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mike at flyn dot org
  Target Milestone: ---

I am using:

       cpp -C -P -nostdinc -std=c99 -Werror

to process something that is not C. Everything works, except that one side
effect of "-P" is that consecutive newlines are compressed into one.

For example,

$ cpp -P
x


x

outputs

x
x

I have not found documentation of this behavior. My hunch is that -P should not
behave this way because the man page states, "this might be useful when running
the preprocessor on something that is not C code." I would think that users
employing cpp to process non-C would expect newlines to be preserved.

I previously brought this up on the GCC mailing list. See
https://gcc.gnu.org/ml/gcc-help/2015-08/msg00069.html.