#if __GNUC__ > 2 ..

#if __GNUC__ > 2 ..

[Jan Nieuwenhuizen]

Hi Matt!

When I use Nyacc to parse things like

     #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96)
     # define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__))
     #else
     # define _GL_ATTRIBUTE_PURE /* empty */
     #endif

I get

    foo.c:1: undefined identifier: "__GNUC__"
    foo.c:1: CPP error

I have been avoiding this using #:cpp-defs '( ... "__GNUC__=0" ) for Mes
but for real projects that put gcc-specific things inside

    #ifdef __GCC__
    #endif

that does not work.  I'm trying to compile different things currently,
like 8cc, pcc and Guile's eval.c-- without much success ATM--, changing
and editing lots of things like these defines but it is getting hairy
now.

Greetings,
janneke

-- 
Jan Nieuwenhuizen <janneke@gnu.org> | GNU LilyPond http://lilypond.org
Freelance IT http://JoyofSource.com | Avatar® http://AvatarAcademy.com

Re: #if __GNUC__ > 2 ..

[Mark H Weaver]

Jan Nieuwenhuizen <janneke@gnu.org> writes:

> Hi Matt!
>
> When I use Nyacc to parse things like
>
>      #if __GNUC__ > 2 || (__GNUC__ == 2 && __GNUC_MINOR__ >= 96)
>      # define _GL_ATTRIBUTE_PURE __attribute__ ((__pure__))
>      #else
>      # define _GL_ATTRIBUTE_PURE /* empty */
>      #endif
>
> I get
>
>     foo.c:1: undefined identifier: "__GNUC__"
>     foo.c:1: CPP error

This looks like a problem in Nyacc.  Within the condition of an "#if" or
"#elif" preprocessor form, after macro expansion is performed, all
remaining identifiers are replaced with 0.  See section 6.10.1
(Conditional inclusion) paragraph 4 of C99.

      Mark

Re: #if __GNUC__ > 2 ..

[Matt Wette]

With patch below, this looks to be working.  I will update and release later today. — Matt

diff --git a/module/nyacc/lang/c99/cpp.scm b/module/nyacc/lang/c99/cpp.scm
index 7ea57f7..511553a 100644
--- a/module/nyacc/lang/c99/cpp.scm
+++ b/module/nyacc/lang/c99/cpp.scm
@@ -230,7 +230,7 @@
            ((or) (if (and (zero? (ev1 tree)) (zero? (ev2 tree))) 0 1))
            ((and) (if (or (zero? (ev1 tree)) (zero? (ev2 tree))) 0 1))
            ((cond-expr) (if (zero? (ev1 tree)) (ev3 tree) (ev2 tree)))
-           ((ident) (cpp-err "undefined identifier: ~S" (cadr tree)))
+           ((ident) 0)
            (else (error "incomplete implementation"))))))
     (eval-expr tree)))
 
@@ -464,6 +464,7 @@
 
 ;; @deffn {Procedure} eval-cpp-cond-text text defs => string
 ;; Evaluate CPP condition expression (text).
+;; Undefined identifiers are replaced with @code{0}.
 ;; @end deffn
 (define (eval-cpp-cond-text text defs)
   (with-throw-handler