Standardize on VIRT_ADDR_VARIES behavior.

Otherwise, valgrind does not work on some platforms.
Problem reported by Andreas Schwab in
<http://lists.gnu.org/archive/html/emacs-devel/2011-11/msg00081.html>.
* puresize.h (pure, PURE_P): Always behave as if VIRT_ADDR_VARIES
is set, removing the need for VIRT_ADDRESS_VARIES.
(PURE_P): Use a more-efficient implementation that needs just one
comparison, not two: on x86-64 with GCC 4.6.2, this cut down the
number of instructions from 6 (xorl, cmpq, jge, xorl, cmpq, setge)
to 4 (xorl, subq, cmpq, setbe).
* alloc.c (pure): Always extern now, since that's the
VIRT_ADDR_VARIES behavior.
(PURE_POINTER_P): Use a single comparison, not two, for
consistency with the new puresize.h.
* lisp.h (PNTR_COMPARISON_TYPE): Remove; no longer needed.
* m/ibms390.h, m/intel386.h, m/template.h, s/cygwin.h, s/hpux10-20.h:
Remove VIRT_ADDR_VARIES no longer needed.

Fixes: debbugs:10042

9 files changed, 25 insertions, 54 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 2973ecc4b57..7accd0d5eea 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,23 @@
+2011-11-20  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Standardize on VIRT_ADDR_VARIES behavior (Bug#10042).
+        Otherwise, valgrind does not work on some platforms.
+        Problem reported by Andreas Schwab in
+        <http://lists.gnu.org/archive/html/emacs-devel/2011-11/msg00081.html>.
+        * puresize.h (pure, PURE_P): Always behave as if VIRT_ADDR_VARIES
+        is set, removing the need for VIRT_ADDRESS_VARIES.
+        (PURE_P): Use a more-efficient implementation that needs just one
+        comparison, not two: on x86-64 with GCC 4.6.2, this cut down the
+        number of instructions from 6 (xorl, cmpq, jge, xorl, cmpq, setge)
+        to 4 (xorl, subq, cmpq, setbe).
+        * alloc.c (pure): Always extern now, since that's the
+        VIRT_ADDR_VARIES behavior.
+        (PURE_POINTER_P): Use a single comparison, not two, for
+        consistency with the new puresize.h.
+        * lisp.h (PNTR_COMPARISON_TYPE): Remove; no longer needed.
+        * m/ibms390.h, m/intel386.h, m/template.h, s/cygwin.h, s/hpux10-20.h:
+        Remove VIRT_ADDR_VARIES no longer needed.
+
 2011-11-19  Eli Zaretskii  <eliz@gnu.org>
 
         * xdisp.c (x_write_glyphs, draw_phys_cursor_glyph)
diff --git a/src/alloc.c b/src/alloc.c
index 5d04bd77872..96d63f53cf9 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -203,9 +203,6 @@ static int malloc_hysteresis;
    remapping on more recent systems because this is less important
    nowadays than in the days of small memories and timesharing.  */
 
-#ifndef VIRT_ADDR_VARIES
-static
-#endif
 EMACS_INT pure[(PURESIZE + sizeof (EMACS_INT) - 1) / sizeof (EMACS_INT)] = {1,};
 #define PUREBEG (char *) pure
 
@@ -222,10 +219,7 @@ static ptrdiff_t pure_bytes_used_before_overflow;
 /* Value is non-zero if P points into pure space.  */
 
 #define PURE_POINTER_P(P)                                       \
-     (((PNTR_COMPARISON_TYPE) (P)                               \
-       < (PNTR_COMPARISON_TYPE) ((char *) purebeg + pure_size)) \
-      && ((PNTR_COMPARISON_TYPE) (P)                            \
-          >= (PNTR_COMPARISON_TYPE) purebeg))
+  ((uintptr_t) (P) - (uintptr_t) purebeg <= pure_size)
 
 /* Index in pure at which next pure Lisp object will be allocated.. */
 
diff --git a/src/lisp.h b/src/lisp.h
index 695141321c9..dcd1167e0a2 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -1877,9 +1877,6 @@ typedef struct {
     CHECK_NATNUM (tmp);                 \
     XSETCDR ((x), tmp);                 \
   } while (0)
-
-/* Cast pointers to this type to compare them.  */
-#define PNTR_COMPARISON_TYPE uintptr_t
 
 /* Define a built-in function for calling from Lisp.
  `lname' should be the name to give the function in Lisp,
diff --git a/src/m/ibms390.h b/src/m/ibms390.h
index c309035dc5c..7269d416a48 100644
--- a/src/m/ibms390.h
+++ b/src/m/ibms390.h
@@ -17,11 +17,6 @@ GNU General Public License for more details.
 You should have received a copy of the GNU General Public License
 along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
-
-/* Define VIRT_ADDR_VARIES if the virtual addresses of
-   pure and impure space as loaded can vary, and even their
-   relative order cannot be relied on.
-
-   Otherwise Emacs assumes that text space precedes data space,
-   numerically.  */
-#define VIRT_ADDR_VARIES
+/* This file is a placeholder -- it does not contain any definitions.
+   At some point we should probably fix this by removing the file
+   and removing all uses of it.  */
diff --git a/src/m/intel386.h b/src/m/intel386.h
index 16f0645715c..114b7fef963 100644
--- a/src/m/intel386.h
+++ b/src/m/intel386.h
@@ -19,7 +19,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 
 
 #ifdef WINDOWSNT
-#define VIRT_ADDR_VARIES
 #define DATA_START      get_data_start ()
 #endif
 
@@ -28,4 +27,3 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
 /* we cannot get the maximum address for brk */
 #define ULIMIT_BREAK_VALUE (32*1024*1024)
 #endif
-
diff --git a/src/m/template.h b/src/m/template.h
index 54fb0da9521..38649e8ac6d 100644
--- a/src/m/template.h
+++ b/src/m/template.h
@@ -21,14 +21,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
    does not define it automatically.
    Ones defined so far include m68k and many others */
 
-/* Define VIRT_ADDR_VARIES if the virtual addresses of
-   pure and impure space as loaded can vary, and even their
-   relative order cannot be relied on.
-
-   Otherwise Emacs assumes that text space precedes data space,
-   numerically.  */
-#define VIRT_ADDR_VARIES
-
 /* After adding support for a new machine, modify the large case
    statement in configure.in to recognize reasonable
    configuration names, and add a description of the system to
diff --git a/src/puresize.h b/src/puresize.h
index c26c496a757..4290c30c68d 100644
--- a/src/puresize.h
+++ b/src/puresize.h
@@ -75,21 +75,7 @@ extern void pure_write_error (void) NO_RETURN;
 
 /* Define PURE_P.  */
 
-#ifdef VIRT_ADDR_VARIES
-/* For machines where text and data can go anywhere
-   in virtual memory.  */
-
 extern EMACS_INT pure[];
 
 #define PURE_P(obj) \
- ((PNTR_COMPARISON_TYPE) XPNTR (obj) < (PNTR_COMPARISON_TYPE) ((char *) pure + PURESIZE) \
-  && (PNTR_COMPARISON_TYPE) XPNTR (obj) >= (PNTR_COMPARISON_TYPE) pure)
-
-#else /* not VIRT_ADDR_VARIES */
-
-extern char my_edata[];
-
-#define PURE_P(obj) \
-  ((PNTR_COMPARISON_TYPE) XPNTR (obj) < (PNTR_COMPARISON_TYPE) my_edata)
-
-#endif /* VIRT_ADDRESS_VARIES */
+  ((uintptr_t) XPNTR (obj) - (uintptr_t) pure <= PURESIZE)
diff --git a/src/s/cygwin.h b/src/s/cygwin.h
index af5308ff7bb..8f5a0ab1fc7 100644
--- a/src/s/cygwin.h
+++ b/src/s/cygwin.h
@@ -91,9 +91,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
    why it needed to be changed.  */
 #define GC_MARK_STACK GC_MAKE_GCPROS_NOOPS
 
-/* Virtual addresses of pure and impure space can vary, as on Windows.  */
-#define VIRT_ADDR_VARIES
-
 /* Emacs supplies its own malloc, but glib (part of Gtk+) calls
    memalign and on Cygwin, that becomes the Cygwin-supplied memalign.
    As malloc is not the Cygwin malloc, the Cygwin memalign always
diff --git a/src/s/hpux10-20.h b/src/s/hpux10-20.h
index 37199bcc29b..be457498add 100644
--- a/src/s/hpux10-20.h
+++ b/src/s/hpux10-20.h
@@ -100,14 +100,6 @@ along with GNU Emacs.  If not, see <http://www.gnu.org/licenses/>.  */
    header sections which lose when `static' is defined away, as it is
    on HP-UX.  (You get duplicate symbol errors on linking). */
 #undef _FILE_OFFSET_BITS
-
-/* Define VIRT_ADDR_VARIES if the virtual addresses of
-   pure and impure space as loaded can vary, and even their
-   relative order cannot be relied on.
-
-   Otherwise Emacs assumes that text space precedes data space,
-   numerically.  */
-#define VIRT_ADDR_VARIES
 
 /* The data segment on this machine always starts at address 0x40000000.  */
 #define DATA_SEG_BITS 0x40000000