pmt: initial 3.0.2 update

include/libgnulib/xsize.h

@@ -0,0 +1,130 @@
+/* xsize.h -- Checked size_t computations.
+
+   Copyright (C) 2003, 2008-2024 Free Software Foundation, Inc.
+
+   This file is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Lesser General Public License as
+   published by the Free Software Foundation; either version 2.1 of the
+   License, or (at your option) any later version.
+
+   This file 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 Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+#ifndef _XSIZE_H
+#define _XSIZE_H
+
+/* This file uses _GL_INLINE_HEADER_BEGIN, _GL_INLINE, HAVE_STDINT_H.  */
+#if !_GL_CONFIG_H_INCLUDED
+ #error "Please include config.h first."
+#endif
+
+/* Get size_t.  */
+#include <stddef.h>
+
+/* Get INT_MAX, SIZE_MAX.  */
+#include <limits.h>
+#if HAVE_STDINT_H
+# include <stdint.h>
+#endif
+
+/* Get ATTRIBUTE_PURE.  */
+#include "attribute.h"
+
+_GL_INLINE_HEADER_BEGIN
+#ifndef XSIZE_INLINE
+# define XSIZE_INLINE _GL_INLINE
+#endif
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+
+/* The size of memory objects is often computed through expressions of
+   type size_t. Example:
+      void* p = malloc (header_size + n * element_size).
+   These computations can lead to overflow.  When this happens, malloc()
+   returns a piece of memory that is way too small, and the program then
+   crashes while attempting to fill the memory.
+   To avoid this, the functions and macros in this file check for overflow.
+   The convention is that SIZE_MAX represents overflow.
+   malloc (SIZE_MAX) is not guaranteed to fail -- think of a malloc
+   implementation that uses mmap --, it's recommended to use size_overflow_p()
+   or size_in_bounds_p() before invoking malloc().
+   The example thus becomes:
+      size_t size = xsum (header_size, xtimes (n, element_size));
+      void *p = (size_in_bounds_p (size) ? malloc (size) : NULL);
+*/
+
+/* Convert an arbitrary N >= 0 to type size_t.
+   N should not have side effects.  */
+#define xcast_size_t(N) \
+  ((N) <= SIZE_MAX ? (size_t) (N) : SIZE_MAX)
+
+/* Sum of two sizes, with overflow check.  */
+XSIZE_INLINE size_t ATTRIBUTE_PURE
+xsum (size_t size1, size_t size2)
+{
+  if (INT_MAX < SIZE_MAX)
+    {
+      /* Optimize for the common case where size_t arithmetic wraps
+         around without undefined behavior.  */
+      size_t sum = size1 + size2;
+      return size1 <= sum ? sum : SIZE_MAX;
+    }
+
+  return size1 <= SIZE_MAX - size2 ? size1 + size2 : SIZE_MAX;
+}
+
+/* Sum of three sizes, with overflow check.  */
+XSIZE_INLINE size_t ATTRIBUTE_PURE
+xsum3 (size_t size1, size_t size2, size_t size3)
+{
+  return xsum (xsum (size1, size2), size3);
+}
+
+/* Sum of four sizes, with overflow check.  */
+XSIZE_INLINE size_t ATTRIBUTE_PURE
+xsum4 (size_t size1, size_t size2, size_t size3, size_t size4)
+{
+  return xsum (xsum (xsum (size1, size2), size3), size4);
+}
+
+/* Maximum of two sizes, with overflow check.  */
+XSIZE_INLINE size_t ATTRIBUTE_PURE
+xmax (size_t size1, size_t size2)
+{
+  /* No explicit check is needed here, because for any n:
+     max (SIZE_MAX, n) == SIZE_MAX and max (n, SIZE_MAX) == SIZE_MAX.  */
+  return (size1 >= size2 ? size1 : size2);
+}
+
+/* Multiplication of a count with an element size, with overflow check.
+   The count must be >= 0 and the element size must be > 0.
+   Arguments should not have side effects.
+   The element size's type should be no wider than size_t.
+   This is a macro, not a function, so that it works correctly even
+   when N is of a wider type and N > SIZE_MAX.  */
+#define xtimes(N, ELSIZE) \
+  ((N) <= SIZE_MAX / (ELSIZE) ? (size_t) (N) * (ELSIZE) : SIZE_MAX)
+
+/* Check for overflow.  */
+#define size_overflow_p(SIZE) \
+  ((SIZE) == SIZE_MAX)
+/* Check against overflow.  */
+#define size_in_bounds_p(SIZE) \
+  ((SIZE) != SIZE_MAX)
+
+
+#ifdef __cplusplus
+}
+#endif
+
+_GL_INLINE_HEADER_END
+
+#endif /* _XSIZE_H */