linux-kernel - [PATCH AUTOSEL 3.18 21/26] unifdef: use memcpy instead of strncpy

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Message-Id: <20181205095430.8019-21-sashal@kernel.org>
Date:   Wed,  5 Dec 2018 04:54:25 -0500
From:   Sasha Levin <sashal@...nel.org>
To:     stable@...r.kernel.org, linux-kernel@...r.kernel.org
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Sasha Levin <sashal@...nel.org>
Subject: [PATCH AUTOSEL 3.18 21/26] unifdef: use memcpy instead of strncpy

From: Linus Torvalds <torvalds@...ux-foundation.org>

[ Upstream commit 38c7b224ce22c25fed04007839edf974bd13439d ]

New versions of gcc reasonably warn about the odd pattern of

	strncpy(p, q, strlen(q));

which really doesn't make sense: the strncpy() ends up being just a slow
and odd way to write memcpy() in this case.

There was a comment about _why_ the code used strncpy - to avoid the
terminating NUL byte, but memcpy does the same and avoids the warning.

Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 scripts/unifdef.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/scripts/unifdef.c b/scripts/unifdef.c
index 7493c0ee51cc..db00e3e30a59 100644
--- a/scripts/unifdef.c
+++ b/scripts/unifdef.c
@@ -395,7 +395,7 @@ usage(void)
  * When we have processed a group that starts off with a known-false
  * #if/#elif sequence (which has therefore been deleted) followed by a
  * #elif that we don't understand and therefore must keep, we edit the
- * latter into a #if to keep the nesting correct. We use strncpy() to
+ * latter into a #if to keep the nesting correct. We use memcpy() to
  * overwrite the 4 byte token "elif" with "if  " without a '\0' byte.
  *
  * When we find a true #elif in a group, the following block will
@@ -450,7 +450,7 @@ static void Idrop (void) { Fdrop();  ignoreon(); }
 static void Itrue (void) { Ftrue();  ignoreon(); }
 static void Ifalse(void) { Ffalse(); ignoreon(); }
 /* modify this line */
-static void Mpass (void) { strncpy(keyword, "if  ", 4); Pelif(); }
+static void Mpass (void) { memcpy(keyword, "if  ", 4); Pelif(); }
 static void Mtrue (void) { keywordedit("else");  state(IS_TRUE_MIDDLE); }
 static void Melif (void) { keywordedit("endif"); state(IS_FALSE_TRAILER); }
 static void Melse (void) { keywordedit("endif"); state(IS_FALSE_ELSE); }
-- 
2.17.1