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std.StaticStringMap: bump eval branch quota

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closes #19803 by changing quota from (30 * N) to (10 * N * log2(N)) where
N = kvs_list.len

* adds reported adversarial test case
* update doc comment of getLongestPrefix()
This commit is contained in:
Travis Staloch 2024-04-30 17:21:44 -07:00 • committed by Andrew Kelley
parent ea9d817a90
commit 44db92d1ca
1 changed files with 39 additions and 4 deletions
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43
lib/std/static_string_map.zig
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@ -70,11 +70,15 @@ pub fn StaticStringMapWithEql(
/// (only keys) tuples if `V` is `void`.
pub inline fn initComptime(comptime kvs_list: anytype) Self {
comptime {
@setEvalBranchQuota(30 * kvs_list.len);
var self = Self{};
if (kvs_list.len == 0)
return self;
// Since the KVs are sorted, a linearly-growing bound will never
// be sufficient for extreme cases. So we grow proportional to
// N*log2(N).
@setEvalBranchQuota(10 * kvs_list.len * std.math.log2_int_ceil(usize, kvs_list.len));
var sorted_keys: [kvs_list.len][]const u8 = undefined;
var sorted_vals: [kvs_list.len]V = undefined;
@ -212,8 +216,12 @@ pub fn StaticStringMapWithEql(
}
}
/// Returns the longest key, value pair where key is a prefix of `str`
/// Returns the key-value pair where key is the longest prefix of `str`
/// else null.
///
/// This is effectively an O(N) algorithm which loops from `max_len` to
/// `min_len` and calls `getIndex()` to check all keys with the given
/// len.
pub fn getLongestPrefix(self: Self, str: []const u8) ?KV {
if (self.kvs.len == 0)
return null;
@ -497,6 +505,33 @@ test "getLongestPrefix2" {
try testing.expectEqual(null, map.getLongestPrefix("xxx"));
}
test "long kvs_list doesn't exceed @setEvalBranchQuota" {
_ = TestMapVoid.initComptime([1]TestKVVoid{.{"x"}} ** 1_000);
test "sorting kvs doesn't exceed eval branch quota" {
// from https://github.com/ziglang/zig/issues/19803
const TypeToByteSizeLUT = std.StaticStringMap(u32).initComptime(.{
.{ "bool", 0 },
.{ "c_int", 0 },
.{ "c_long", 0 },
.{ "c_longdouble", 0 },
.{ "t20", 0 },
.{ "t19", 0 },
.{ "t18", 0 },
.{ "t17", 0 },
.{ "t16", 0 },
.{ "t15", 0 },
.{ "t14", 0 },
.{ "t13", 0 },
.{ "t12", 0 },
.{ "t11", 0 },
.{ "t10", 0 },
.{ "t9", 0 },
.{ "t8", 0 },
.{ "t7", 0 },
.{ "t6", 0 },
.{ "t5", 0 },
.{ "t4", 0 },
.{ "t3", 0 },
.{ "t2", 0 },
.{ "t1", 1 },
});
try testing.expectEqual(1, TypeToByteSizeLUT.get("t1"));
}