From: Pascal Cuoq <cuoq@trust-in-soft.com>
To: "musl@lists.openwall.com" <musl@lists.openwall.com>
Subject: patch: sequence points in memset
Date: Mon, 10 Jul 2017 14:39:07 +0000 [thread overview]
Message-ID: <CF3F2019-214F-487B-A7DC-7E88B0F2D4A1@trust-in-soft.com> (raw)
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Following a recent discussion of statements shaped like x = x = c;, the attached patch introduces additional sequence points in musl's implementation of memset, because no realistic target platform benefits from the lack of sequence points in the current version, and if a hypothetical target (VLIW maybe?) was designed to benefit from the lack of sequence point, the lack of sequence point might just as well cause harm.
Pascal
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diff --git a/src/string/memset.c b/src/string/memset.c
index f438b07..5613a14 100644
--- a/src/string/memset.c
+++ b/src/string/memset.c
@@ -11,12 +11,16 @@ void *memset(void *dest, int c, size_t n)
* offsets are well-defined and in the dest region. */
if (!n) return dest;
- s[0] = s[n-1] = c;
+ s[0] = c;
+ s[n-1] = c;
if (n <= 2) return dest;
- s[1] = s[n-2] = c;
- s[2] = s[n-3] = c;
+ s[1] = c;
+ s[2] = c;
+ s[n-2] = c;
+ s[n-3] = c;
if (n <= 6) return dest;
- s[3] = s[n-4] = c;
+ s[3] = c;
+ s[n-4] = c;
if (n <= 8) return dest;
/* Advance pointer to align it at a 4-byte boundary,
next reply other threads:[~2017-07-10 14:39 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-07-10 14:39 Pascal Cuoq [this message]
2017-07-10 15:10 ` Alexander Monakov
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