Porting fixes for merged specpdl and backtrace stacks.

In particular this ports to 32-bit sparc Sun cc.
* eval.c (init_eval_once, grow_specpdl): Allocate a specbinding
array with a dummy element at specpdl[-1], so that its address can
be taken portably.
(unbind_to): Do not copy the binding; not needed, now that we
copy old_value in the one place where the copy is needed.
* fileio.c (Fwrite_region): Use ptrdiff_t, not int, for specpdl count.
* lisp.h (BITS_PER_PTRDIFF_T): Remove; no longer needed.
(union specbinding): Rename from struct specbinding.  Redo layout
to avoid the need for 'ptrdiff_t nargs : BITS_PER_PTRDIFF_T - 1;',
which is not portable.  With Sun C 5.12 32-bit sparc, the
declaration causes nargs to be an unsigned bitfield, a behavior
that the C standard allows; but Emacs wants nargs to be signed.
The overall type is now a union of structures rather than a
structure of union of structures, and the 'kind' member is now a
bitfield, so that the overall type doesn't grow.  All uses changed.
* process.c (Fmake_serial_process): Remove unnecessary initialization.

Fixes: debbugs:14643

1 files changed, 21 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 9a23c144e82..e1609356403 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,24 @@
+2013-06-18  Paul Eggert  <eggert@cs.ucla.edu>
+
+        Porting fixes for merged specpdl and backtrace stacks (Bug#14643).
+        In particular this ports to 32-bit sparc Sun cc.
+        * eval.c (init_eval_once, grow_specpdl): Allocate a specbinding
+        array with a dummy element at specpdl[-1], so that its address can
+        be taken portably.
+        (unbind_to): Do not copy the binding; not needed, now that we
+        copy old_value in the one place where the copy is needed.
+        * fileio.c (Fwrite_region): Use ptrdiff_t, not int, for specpdl count.
+        * lisp.h (BITS_PER_PTRDIFF_T): Remove; no longer needed.
+        (union specbinding): Rename from struct specbinding.  Redo layout
+        to avoid the need for 'ptrdiff_t nargs : BITS_PER_PTRDIFF_T - 1;',
+        which is not portable.  With Sun C 5.12 32-bit sparc, the
+        declaration causes nargs to be an unsigned bitfield, a behavior
+        that the C standard allows; but Emacs wants nargs to be signed.
+        The overall type is now a union of structures rather than a
+        structure of union of structures, and the 'kind' member is now a
+        bitfield, so that the overall type doesn't grow.  All uses changed.
+        * process.c (Fmake_serial_process): Remove unnecessary initialization.
+
 2013-06-17  Paul Eggert  <eggert@cs.ucla.edu>
 
         * frame.c (x_report_frame_params): Cast parent_desc to uintptr_t.