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avoid constant overflow when shifting left signed integers until

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their last bit
This commit is contained in:
Roberto Ierusalimschy 2014-04-03 10:29:24 -03:00
parent 3a044de5a1
commit 48c745a611
1 changed files with 5 additions and 5 deletions
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10
lstrlib.c
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@ -1,5 +1,5 @@
/*
** $Id: lstrlib.c,v 1.190 2014/03/27 15:58:05 roberto Exp roberto $
** $Id: lstrlib.c,v 1.191 2014/03/31 18:38:26 roberto Exp roberto $
** Standard library for string operations and pattern-matching
** See Copyright Notice in lua.h
*/
@ -954,10 +954,10 @@ static int str_format (lua_State *L) {
#define NB CHAR_BIT
/* mask for one character (NB ones) */
#define MC (((lua_Integer)1 << NB) - 1)
#define MC ((1 << NB) - 1)
/* mask for one character without sign ((NB - 1) ones) */
#define SM (((lua_Integer)1 << (NB - 1)) - 1)
#define SM ((1 << (NB - 1)) - 1)
#define SZINT ((int)sizeof(lua_Integer))
@ -1007,7 +1007,7 @@ static int packint (char *buff, lua_Integer n, int littleendian, int size) {
/* test for overflow: OK if there are only zeros left in higher bytes,
or if there are only ones left and packed number is negative (signal
bit, the higher bit in last byte, is one) */
return ((n & ~MC) == 0 || (n | SM) == ~(lua_Integer)0);
return ((n & ~(lua_Integer)MC) == 0 || (n | SM) == ~(lua_Integer)0);
}
@ -1025,7 +1025,7 @@ static int packint_l (lua_State *L) {
/* mask to check higher-order byte in a Lua integer */
#define HIGHERBYTE (MC << (NB * (SZINT - 1)))
#define HIGHERBYTE ((lua_Unsigned)MC << (NB * (SZINT - 1)))
/* mask to check higher-order byte + signal bit of next (lower) byte */
#define HIGHERBYTE1 (HIGHERBYTE | (HIGHERBYTE >> 1))