Port to IRIX 6.5.

This port requires IRIX cc, as I did not have time to get
undump working with the old GCC on the system I had access to,
but that's better than nothing.
* configure.ac (gl_GCC_VERSION_IFELSE): Remove unused macro
that wouldn't have worked anyway, with IRIX cc.
(emacs_cv_clang, emacs_cv_sanitize_address)
(ns_osx_have_104, ns_osx_have_105):
Don't assume '#error' makes the compiler fail,
as this doesn't work with IRIX cc.
(CFLAGS, LIBS): Don't let the GnuTLS results infect later 'configure'
checks.  This runs afoul of an IRIX configuration where GnuTLS is
in an optional library that also contains getdelim, and causes
a later 'configure' to incorrectly think getdelim is supported.
* src/alloc.c (TAGGABLE_NULL): New constant,
for porting to hosts with nontrivial DATA_SEG_BITS settings.
(next_vector, set_next_vector): Use it.
* src/conf_post.h (INET6) [IRIX6_5]: Define.
(HAVE_GETADDRINFO) [IRIX6_5]: Undef.
* src/data.c (BITS_PER_ULL): Don't assume ULLONG_MAX is defined.
* src/lisp.h (lisp_h_XPNTR): Don't OR in bits that aren't masked out,
for consistency with how TAGGABLE_NULL is computed.

Fixes: debbugs:9684

1 files changed, 8 insertions, 2 deletions

diff --git a/src/alloc.c b/src/alloc.c
index d4e24b6244b..ccb955a547b 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -2647,18 +2647,24 @@ DEFUN ("make-list", Fmake_list, Smake_list, 2, 2, 0,
  ***********************************************************************/
 
 /* Sometimes a vector's contents are merely a pointer internally used
-   in vector allocation code.  Usually you don't want to touch this.  */
+   in vector allocation code.  On the rare platforms where a null
+   pointer cannot be tagged, represent it with a Lisp 0.
+   Usually you don't want to touch this.  */
+
+enum { TAGGABLE_NULL = (DATA_SEG_BITS & ~VALMASK) == 0 };
 
 static struct Lisp_Vector *
 next_vector (struct Lisp_Vector *v)
 {
+  if (! TAGGABLE_NULL && EQ (v->contents[0], make_number (0)))
+    return 0;
   return XUNTAG (v->contents[0], 0);
 }
 
 static void
 set_next_vector (struct Lisp_Vector *v, struct Lisp_Vector *p)
 {
-  v->contents[0] = make_lisp_ptr (p, 0);
+  v->contents[0] = TAGGABLE_NULL || p ? make_lisp_ptr (p, 0) : make_number (0);
 }
 
 /* This value is balanced well enough to avoid too much internal overhead