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avoid undefined shift of LUA_NBITS in rotate operation

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Roberto Ierusalimschy 2013-07-09 15:31:01 -03:00
parent 5fa680d47f
commit 2ef9bcfd11
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 1.20 2013/06/21 17:27:24 roberto Exp roberto $
** $Id: lbitlib.c,v 1.21 2013/07/09 17:49:50 roberto Exp roberto $
** Standard library for bitwise operations
** See Copyright Notice in lua.h
*/
@ -128,7 +128,8 @@ static int b_rot (lua_State *L, int i) {
lua_Unsigned 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;
}