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avoid (undefined behavior) integer 'overflow' in left shift

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Roberto Ierusalimschy
2015-10-08 12:55:35 -03:00
parent 0c78de0d6d
commit 1a741157cb
1 changed files with 4 additions and 5 deletions
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9
lbitlib.c
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@@ -1,5 +1,5 @@
/* /*
** $Id: lbitlib.c,v 1.27 2014/10/01 11:54:56 roberto Exp roberto $ ** $Id: lbitlib.c,v 1.28 2014/11/02 19:19:04 roberto Exp roberto $
** Standard library for bitwise operations ** Standard library for bitwise operations
** See Copyright Notice in lua.h ** See Copyright Notice in lua.h
*/ */
@@ -186,11 +186,10 @@ static int b_extract (lua_State *L) {
static int b_replace (lua_State *L) { static int b_replace (lua_State *L) {
int w; int w;
lua_Unsigned r = trim(luaL_checkunsigned(L, 1)); lua_Unsigned r = trim(luaL_checkunsigned(L, 1));
lua_Unsigned v = luaL_checkunsigned(L, 2); lua_Unsigned v = trim(luaL_checkunsigned(L, 2));
int f = fieldargs(L, 3, &w); int f = fieldargs(L, 3, &w);
int m = mask(w); lua_Unsigned m = mask(w);
v &= m; /* erase bits outside given width */ r = (r & ~(m << f)) | ((v & m) << f);
r = (r & ~(m << f)) | (v << f);
lua_pushunsigned(L, r); lua_pushunsigned(L, r);
return 1; return 1;
} }