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avoid undefined shift of LUA_NBITS in rotate operations

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Roberto Ierusalimschy 2013-07-09 15:01:41 -03:00
parent d2209c0741
commit 42cf5f8214
1 changed files with 3 additions and 2 deletions
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5
lbitlib.c
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@ -1,5 +1,5 @@
/*
** $Id: lbitlib.c,v 1.18 2013/03/19 13:19:12 roberto Exp $
** $Id: lbitlib.c,v 1.18.1.1 2013/04/12 18:48:47 roberto Exp roberto $
** Standard library for bitwise operations
** See Copyright Notice in lua.h
*/
@ -129,7 +129,8 @@ static int b_rot (lua_State *L, int i) {
b_uint r = luaL_checkunsigned(L, 1);
i &= (LUA_NBITS - 1); /* i = i % NBITS */
r = trim(r);
r = (r << i) | (r >> (LUA_NBITS - i));
if (i != 0) /* avoid undefined shift of LUA_NBITS when i == 0 */
r = (r << i) | (r >> (LUA_NBITS - i));
lua_pushunsigned(L, trim(r));
return 1;
}