Re: warning: pasting would not give a valid preprocessing token

[Jeffrey A Law <law at cygnus dot com>]

  In message <20000914235302.A9969@daikokuya.demon.co.uk>you write:
  > [There's no point cc-ing Zack; his mail address is no more]
  > 
  > Byron,
  > 
  > I hope this fixes it for you.  I'm bootstrapping now, and will then
  > run the testsuite.
  > 
  > This area is a bit ugly and in bad need of a cleanup.  I need to
  > extract more flexibility from the lexer first, though.  The problem
  > was in the way we handle macro arguments: each argument is a list of
  > pointers to the tokens making up the argument.  These tend to point to
  > the original tokens (in this case, the comma in the macro definition
  > in the hash table).  That token has a PASTE_LEFT flag to say it's on
  > the left hand side of a ##.  The problem is that after processing the
  > paste, and correctly not emitting a warning about invalid pastes, we
  > maintained a pointer to the same comma for the nested macro
  > replacements (since it is part of an argument itself).  Unforunately,
  > of course, that comma still has its paste flag set, so the paste
  > mechanism gets re-invoked in later unintended places; hence the
  > (repeated) warnings.
  > 
  > This is a nice testcase for quite a deep nested macro bug.  I
  > simplified your case to the one below, which I'll commit along with
  > the fix.  If you have a chance, please give it a whirl.
  > 
  > It also fixes a bug in ON_REST_ARG - the macro was testing the flags
  > of the wrong thing (easy to do since #defines are typeless).  Any
  > relief the original fix brought might therefore be undone; I'd be
  > interested in knowing if the warnings it "cured" come back with this
  > patch.
  > 
  > OK to commit?
  > 
  > Neil.
  > 
  > 	* cpplex.c (ON_REST_ARG): Correct the test.
  > 	(maybe_paste_with_next): Duplicate a token that fail pasting,
  > 	and clear its PASTE_LEFT flag, so that nested pasting attempts
  > 	do not occur.
  > 	* gcc.dg/cpp/paste10.c: Testcase.
Assuming the bootstrap & test passes, this is fine to install.

jeff