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std: Don't hash undefined bits

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auto_hash must be extra careful when hashing integers whose bit size is
not a multiple of 8 as, when reinterpreted with mem.asBytes, may contain
undefined non-zero bits too.
This commit is contained in:
LemonBoy 2020-12-17 12:00:48 +01:00
parent 9e5869262a
commit 135f4791e5
1 changed files with 10 additions and 1 deletions
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11
lib/std/hash/auto_hash.zig
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@ -99,7 +99,16 @@ pub fn hash(hasher: anytype, key: anytype, comptime strat: HashStrategy) void {
// Help the optimizer see that hashing an int is easy by inlining!
// TODO Check if the situation is better after #561 is resolved.
.Int => @call(.{ .modifier = .always_inline }, hasher.update, .{std.mem.asBytes(&key)}),
.Int => {
if (comptime meta.trait.hasUniqueRepresentation(Key)) {
@call(.{ .modifier = .always_inline }, hasher.update, .{std.mem.asBytes(&key)});
} else {
// Take only the part containing the key value, the remaining
// bytes are undefined and must not be hashed!
const byte_size = comptime std.math.divCeil(comptime_int, @bitSizeOf(Key), 8) catch unreachable;
@call(.{ .modifier = .always_inline }, hasher.update, .{std.mem.asBytes(&key)[0..byte_size]});
}
},
.Bool => hash(hasher, @boolToInt(key), strat),
.Enum => hash(hasher, @enumToInt(key), strat),