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-rw-r--r--lib/xalloc-oversized.h47
1 files changed, 26 insertions, 21 deletions
diff --git a/lib/xalloc-oversized.h b/lib/xalloc-oversized.h
index d25596932..4184f3395 100644
--- a/lib/xalloc-oversized.h
+++ b/lib/xalloc-oversized.h
@@ -2,12 +2,12 @@
Copyright (C) 1990-2000, 2003-2004, 2006-2021 Free Software Foundation, Inc.
- This program 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 3 of the License, or
- (at your option) any later version.
+ 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 program is distributed in the hope that it will be useful,
+ 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.
@@ -22,33 +22,38 @@
#include <stdint.h>
/* True if N * S does not fit into both ptrdiff_t and size_t.
- S must be positive and N must be nonnegative.
+ N and S should be nonnegative and free of side effects.
This expands to a constant expression if N and S are both constants.
By gnulib convention, SIZE_MAX represents overflow in size_t
calculations, so the conservative size_t-based dividend to use here
is SIZE_MAX - 1. */
#define __xalloc_oversized(n, s) \
- ((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) < (n))
+ ((s) != 0 \
+ && ((size_t) (PTRDIFF_MAX < SIZE_MAX ? PTRDIFF_MAX : SIZE_MAX - 1) / (s) \
+ < (n)))
-#if PTRDIFF_MAX < SIZE_MAX
-typedef ptrdiff_t xalloc_count_t;
-#else
-typedef size_t xalloc_count_t;
-#endif
+/* Return 1 if and only if an array of N objects, each of size S,
+ cannot exist reliably because its total size in bytes would exceed
+ MIN (PTRDIFF_MAX, SIZE_MAX - 1).
+
+ N and S should be nonnegative and free of side effects.
+
+ Warning: (xalloc_oversized (N, S) ? NULL : malloc (N * S)) can
+ misbehave if N and S are both narrower than ptrdiff_t and size_t,
+ and can be rewritten as (xalloc_oversized (N, S) ? NULL
+ : malloc (N * (size_t) S)).
-/* Return 1 if an array of N objects, each of size S, cannot exist reliably
- because its total size in bytes exceeds MIN (PTRDIFF_MAX, SIZE_MAX).
- N must be nonnegative, S must be positive, and either N or S should be
- of type ptrdiff_t or size_t or wider. This is a macro, not a function,
- so that it works even if an argument exceeds MAX (PTRDIFF_MAX, SIZE_MAX). */
-#if 7 <= __GNUC__ && !defined __clang__
+ This is a macro, not a function, so that it works even if an
+ argument exceeds MAX (PTRDIFF_MAX, SIZE_MAX). */
+#if 7 <= __GNUC__ && !defined __clang__ && PTRDIFF_MAX < SIZE_MAX
# define xalloc_oversized(n, s) \
- __builtin_mul_overflow_p (n, s, (xalloc_count_t) 1)
-#elif 5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__
+ __builtin_mul_overflow_p (n, s, (ptrdiff_t) 1)
+#elif (5 <= __GNUC__ && !defined __ICC && !__STRICT_ANSI__ \
+ && PTRDIFF_MAX < SIZE_MAX)
# define xalloc_oversized(n, s) \
(__builtin_constant_p (n) && __builtin_constant_p (s) \
? __xalloc_oversized (n, s) \
- : ({ xalloc_count_t __xalloc_count; \
+ : ({ ptrdiff_t __xalloc_count; \
__builtin_mul_overflow (n, s, &__xalloc_count); }))
/* Other compilers use integer division; this may be slower but is