Port to gcc -fcheck-pointer-bounds

This is a minimal port, just to get Emacs running;
it does not attempt to make the pointer bounds at all tight.
* src/ptr-bounds.h: New file.
* src/alloc.c, src/gmalloc.c: Include it.
* src/alloc.c (live_string_holding, live_cons_holding)
(live_symbol_holding, live_misc_holding, garbage_collect_1)
(sweep_conses, sweep_floats):
* src/gmalloc.c (malloc_initialize_1, _free_internal_nolock)
(_realloc_internal_nolock):
Widen pointer bounds as necessary.
We're in a memory allocator so this is OK.
* src/lisp.h (lisp_h_XSYMBOL, make_lisp_symbol) [__CHKP__]:
Do not convert from pointer to integer and back again, so
that GCC does not lose track of pointer bounds.
(XSYMBOL) [__CHKP__ && !USE_LSB_TAG]: Now a compile-time error.
Although it's possible to support both -fcheck-pointer-bounds and
--with-wide-int, it's more work; keep things simple for now.
(DEFINE_LISP_SYMBOL) [__CHKP__]: Now a no-op, to avoid
trouble with unbounded pointers.

1 files changed, 52 insertions, 0 deletions

diff --git a/src/ptr-bounds.h b/src/ptr-bounds.h
new file mode 100644
index 00000000000..54979824c05
--- /dev/null
+++ b/src/ptr-bounds.h
@@ -0,0 +1,52 @@
+/* Pointer bounds checking for GNU Emacs
+
+Copyright 2017 Free Software Foundation, Inc.
+
+This file is part of GNU Emacs.
+
+GNU Emacs is free software: you can redistribute it and/or modify
+it under the terms of the GNU General Public License as published by
+the Free Software Foundation, either version 3 of the License, or (at
+your option) any later version.
+
+GNU Emacs is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+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 <https://www.gnu.org/licenses/>.  */
+
+#ifndef PTR_BOUNDS_H
+#define PTR_BOUNDS_H
+
+#include <stddef.h>
+
+/* When not checking pointer bounds, the following macros simply
+   return their first argument.  These macros return either void *, or
+   the same type as their first argument.  */
+
+/* Return a copy of P, but with the bounds of Q.  */
+#ifdef __CHKP__
+# define ptr_bounds_copy(p, q) __builtin___bnd_copy_ptr_bounds (p, q)
+#else
+# define ptr_bounds_copy(p, q) ((void) (void const *) {q}, p)
+#endif
+
+/* Return a copy of P, but with infinite bounds.
+   This is a loophole in pointer bounds checking.  */
+#ifdef __CHKP__
+# define ptr_bounds_init(p) __builtin___bnd_init_ptr_bounds (p)
+#else
+# define ptr_bounds_init(p) (p)
+#endif
+
+/* Return a copy of P, but with bounds [P, P + N).
+   This is a loophole in pointer bounds checking.  */
+#ifdef __CHKP__
+# define ptr_bounds_set(p, n) __builtin___bnd_set_ptr_bounds (p, n)
+#else
+# define ptr_bounds_set(p, n) ((void) (size_t) {n}, p)
+#endif
+
+#endif /* PTR_BOUNDS_H */