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Small simplification in overflow check in 'getfield'

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Subtracting a small non-negative int from a non-negative int cannot
overflow, and adding a non-negative int to INT_MIN cannot overflow.
This commit is contained in:
Roberto Ierusalimschy 2022-09-23 10:57:35 -03:00
parent a1089b415a
commit cfbe378f90
2 changed files with 10 additions and 3 deletions
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4
loslib.c
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@ -260,9 +260,7 @@ static int getfield (lua_State *L, const char *key, int d, int delta) {
res = d; res = d;
} }
else { else {
/* unsigned avoids overflow when lua_Integer has 32 bits */ if (!(res >= 0 ? res - delta <= INT_MAX : INT_MIN + delta <= res))
if (!(res >= 0 ? (lua_Unsigned)res <= (lua_Unsigned)INT_MAX + delta
: (lua_Integer)INT_MIN + delta <= res))
return luaL_error(L, "field '%s' is out-of-bound", key); return luaL_error(L, "field '%s' is out-of-bound", key);
res -= delta; res -= delta;
} }

9
testes/files.lua
View File

@ -825,8 +825,17 @@ checkerr("missing", os.time, {hour = 12}) -- missing date
if string.packsize("i") == 4 then -- 4-byte ints if string.packsize("i") == 4 then -- 4-byte ints
checkerr("field 'year' is out-of-bound", os.time, checkerr("field 'year' is out-of-bound", os.time,
{year = -(1 << 31) + 1899, month = 1, day = 1}) {year = -(1 << 31) + 1899, month = 1, day = 1})
checkerr("field 'year' is out-of-bound", os.time,
{year = -(1 << 31), month = 1, day = 1})
if math.maxinteger > 2^31 then -- larger lua_integer?
checkerr("field 'year' is out-of-bound", os.time,
{year = (1 << 31) + 1900, month = 1, day = 1})
end
end end
if not _port then if not _port then
-- test Posix-specific modifiers -- test Posix-specific modifiers
assert(type(os.date("%Ex")) == 'string') assert(type(os.date("%Ex")) == 'string')