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This new function computes the alignment of a pointer. It is part of ISO/IEC 9899:2024, the new C standard. If the pointer is a null pointer, null is returned. I have tried to write an implementation that can cope with traditional address-based architectures, even if size_t and uintptr_t are of different length. Adjustments may be needed for CHERI though. A man page is provided, too. No unit test for now. Reviewed by: kib, imp, ziaee (manpages), pauamma@gundo.com Approved by: markj (mentor) MFC after: 1 month Relnotes: yes Differential Revision: https://reviews.freebsd.org/D53673 (cherry picked from commit 6c57e368eb1777f6097158eeca2fcc175d068dba)
28 lines
452 B
C
28 lines
452 B
C
/*
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* Copyright (c) 2025 Robert Clausecker <fuz@FreeBSD.org>
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*
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* SPDX-License-Identifier: BSD-2-Clause
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*/
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#include <stdint.h>
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#include <stdlib.h>
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size_t
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memalignment(const void *p)
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{
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uintptr_t align;
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if (p == NULL)
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return (0);
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align = (uintptr_t)p;
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align &= -align;
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#if UINTPTR_MAX > SIZE_MAX
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/* if alignment overflows size_t, return maximum possible */
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if (align > SIZE_MAX)
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align = SIZE_MAX - SIZE_MAX/2;
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#endif
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return (align);
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}
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