[Bug c/70270] Spurious line directive with -g

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=70270

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|preprocessor                |c

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
This actually coming from the C/C++ common part of the front-end and not from
the preprocessor:
void
pp_dir_change (cpp_reader *pfile ATTRIBUTE_UNUSED, const char *dir)
{
  size_t to_file_len = strlen (dir);
  unsigned char *to_file_quoted =
     (unsigned char *) alloca (to_file_len * 4 + 1);
  unsigned char *p;

  /* cpp_quote_string does not nul-terminate, so we have to do it ourselves. 
*/
  p = cpp_quote_string (to_file_quoted, (const unsigned char *) dir,
to_file_len);
  *p = '\0';
  fprintf (print.outf, "# 1 \"%s//\"\n", to_file_quoted);
}

And when read back in it invokes cb_dir_change:
  cb->dir_change = cb_dir_change;
...
void
cb_dir_change (cpp_reader * ARG_UNUSED (pfile), const char *dir)
{
  if (!set_src_pwd (dir))
    warning (0, "too late for # directive to set debug directory");
}

So I don't think it changes the different line-map behavior at all.

The first two lines are special in the preprocessed source for libcpp:
/* For preprocessed files, if the very first characters are
   '#<SPACE>[01]<SPACE>', then handle a line directive so we know the
   original file name.  This will generate file_change callbacks,
   which the front ends must handle appropriately given their state of
   initialization.  We peek directly into the character buffer, so
   that we're not confused by otherwise-skipped white space &
   comments.  We can be very picky, because this should have been
   machine-generated text (by us, no less).  This way we do not
   interfere with the module directive state machine.  */

....
/* For preprocessed files, if the tokens following the first filename
   line is of the form # <line> "/path/name//", handle the
   directive so we know the original current directory.

   As with the first line peeking, we can do this without lexing by
   being picky.  */


So I don't think the line mapping changes at all with this.