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No need for 'volatile' in string.pack/unpack

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Type punning an address to 'char *' should be always safe.
This commit is contained in:
Roberto Ierusalimschy
2020-10-05 10:38:41 -03:00
parent 0085db4596
commit fb172d0a92
1 changed files with 7 additions and 10 deletions
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17
lstrlib.c
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@@ -1365,7 +1365,6 @@ typedef union Ftypes {
float f; float f;
double d; double d;
lua_Number n; lua_Number n;
char buff[5 * sizeof(lua_Number)]; /* enough for any float type */
} Ftypes; } Ftypes;
@@ -1535,12 +1534,10 @@ static void packint (luaL_Buffer *b, lua_Unsigned n,
** Copy 'size' bytes from 'src' to 'dest', correcting endianness if ** Copy 'size' bytes from 'src' to 'dest', correcting endianness if
** given 'islittle' is different from native endianness. ** given 'islittle' is different from native endianness.
*/ */
static void copywithendian (volatile char *dest, volatile const char *src, static void copywithendian (char *dest, const char *src,
int size, int islittle) { int size, int islittle) {
if (islittle == nativeendian.little) { if (islittle == nativeendian.little)
while (size-- != 0) memcpy(dest, src, size);
*(dest++) = *(src++);
}
else { else {
dest += size - 1; dest += size - 1;
while (size-- != 0) while (size-- != 0)
@@ -1584,14 +1581,14 @@ static int str_pack (lua_State *L) {
break; break;
} }
case Kfloat: { /* floating-point options */ case Kfloat: { /* floating-point options */
volatile Ftypes u; Ftypes u;
char *buff = luaL_prepbuffsize(&b, size); char *buff = luaL_prepbuffsize(&b, size);
lua_Number n = luaL_checknumber(L, arg); /* get argument */ lua_Number n = luaL_checknumber(L, arg); /* get argument */
if (size == sizeof(u.f)) u.f = (float)n; /* copy it into 'u' */ if (size == sizeof(u.f)) u.f = (float)n; /* copy it into 'u' */
else if (size == sizeof(u.d)) u.d = (double)n; else if (size == sizeof(u.d)) u.d = (double)n;
else u.n = n; else u.n = n;
/* move 'u' to final result, correcting endianness if needed */ /* move 'u' to final result, correcting endianness if needed */
copywithendian(buff, u.buff, size, h.islittle); copywithendian(buff, (char *)&u, size, h.islittle);
luaL_addsize(&b, size); luaL_addsize(&b, size);
break; break;
} }
@@ -1717,9 +1714,9 @@ static int str_unpack (lua_State *L) {
break; break;
} }
case Kfloat: { case Kfloat: {
volatile Ftypes u; Ftypes u;
lua_Number num; lua_Number num;
copywithendian(u.buff, data + pos, size, h.islittle); copywithendian((char *)&u, data + pos, size, h.islittle);
if (size == sizeof(u.f)) num = (lua_Number)u.f; if (size == sizeof(u.f)) num = (lua_Number)u.f;
else if (size == sizeof(u.d)) num = (lua_Number)u.d; else if (size == sizeof(u.d)) num = (lua_Number)u.d;
else num = u.n; else num = u.n;