[libc-commits] [libc] [libc] Fix the -Wshadow errors in perfect_hash_map.h (PR #236585)
via libc-commits
libc-commits at lists.llvm.org
Wed Oct 28 15:02:07 PDT 2026
llvmorg-github-actions[bot] wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-libc
Author: Mike Lothian (FireBurn)
<details>
<summary>Changes</summary>
Building with LIBC_CONF_WCTYPE_MODE=LIBC_WCTYPE_MODE_UTF8 fails under libc's default -Werror, because perfect_hash_map.h has nine declarations that shadow a field or an outer local. No upstream bot builds the UTF8 mode, so nothing has caught it
Rename the shadowing names: the pilots parameters and local become pilot_values and computed_pilots, and the inner loop variables become item_slot, evicted_hp, evicted_item and prior. Each inner variable is renamed only in the scope that declares it, and the outer one is still the one used after the inner loop, so behaviour is unchanged
I checked this by building check-libc in UTF8 mode with the tests and experimental entrypoints on and -Werror left on, on top of #<!-- -->236576 (the tests do not configure in that mode without it), which passed 2302 of 2302. Without this change the same build stops with the -Wshadow errors in wctype_conversion_utils.cpp
AI disclosure: this patch was written with Claude Code. I reviewed the change and ran the build and tests as described above
Assisted-by: Claude
---
Full diff: https://github.com/llvm/llvm-project/pull/236585.diff
1 Files Affected:
- (modified) libc/src/__support/wctype/perfect_hash_map.h (+28-26)
``````````diff
diff --git a/libc/src/__support/wctype/perfect_hash_map.h b/libc/src/__support/wctype/perfect_hash_map.h
index 91b33c8655aacf..5785082a489791 100644
--- a/libc/src/__support/wctype/perfect_hash_map.h
+++ b/libc/src/__support/wctype/perfect_hash_map.h
@@ -229,7 +229,7 @@ class PtrHash {
for (size_t i = 0; i < slots_; i++)
t[i] = 0;
- PilotsTypeV pilots{};
+ PilotsTypeV computed_pilots{};
size_t tries = 0;
constexpr size_t MAX_TRIES = 10;
@@ -248,20 +248,20 @@ class PtrHash {
return {};
this->seed = STDRNG[tries - 1];
- pilots = PilotsTypeV{0};
+ computed_pilots = PilotsTypeV{0};
for (auto &t : taken)
- for (size_t e = 0; e < pilots.size(); e++)
+ for (size_t e = 0; e < computed_pilots.size(); e++)
t[e] = false;
auto shard_hashes = this->shards(keys);
- contd = !this->try_build_shards(shard_hashes, pilots, taken)
+ contd = !this->try_build_shards(shard_hashes, computed_pilots, taken)
? true
: !this->remap_free_slots(taken);
}
- this->pilots = pilots;
+ this->pilots = computed_pilots;
return {{this->seed, this->pilots, this->remap}};
}
@@ -413,13 +413,13 @@ class PtrHash {
LIBC_INLINE constexpr bool
try_build_shards(const cpp::array<cpp::array<uint64_t, n_>, 1> &shard_hashes,
- PilotsTypeV &pilots,
+ PilotsTypeV &pilot_values,
cpp::array<cpp::array<bool, slots_>, parts_> &taken) const {
const size_t pilots_chunk_size =
cpp::max(buckets_ * parts_per_shard_, static_cast<size_t>(1));
const size_t taken_chunk_size = parts_per_shard_;
const size_t num_pilots_chunks =
- (pilots.size() + pilots_chunk_size - 1) / pilots_chunk_size;
+ (pilot_values.size() + pilots_chunk_size - 1) / pilots_chunk_size;
const size_t num_taken_chunks =
(taken.size() + taken_chunk_size - 1) / taken_chunk_size;
@@ -431,7 +431,7 @@ class PtrHash {
size_t pilots_begin = shard * pilots_chunk_size;
size_t pilots_end =
- cpp::min(pilots_begin + pilots_chunk_size, pilots.size());
+ cpp::min(pilots_begin + pilots_chunk_size, pilot_values.size());
size_t taken_begin = shard * taken_chunk_size;
size_t taken_end = cpp::min(taken_begin + taken_chunk_size, taken.size());
@@ -445,7 +445,7 @@ class PtrHash {
auto &[new_hashes, part_starts] = sorted_parts.value();
- if (!this->build_shard(shard, new_hashes, part_starts, pilots,
+ if (!this->build_shard(shard, new_hashes, part_starts, pilot_values,
pilots_begin, pilots_end, taken_begin, taken_end,
taken))
return false;
@@ -457,7 +457,7 @@ class PtrHash {
LIBC_INLINE constexpr bool
build_shard(size_t shard, cpp::array<uint64_t, n_> &hashes,
cpp::array<uint32_t, parts_per_shard_ + 1> &part_starts,
- PilotsTypeV &pilots, size_t pilots_begin, size_t pilots_end,
+ PilotsTypeV &pilot_values, size_t pilots_begin, size_t pilots_end,
size_t taken_begin, size_t taken_end,
cpp::array<cpp::array<bool, slots_>, parts_> &taken) const {
@@ -477,9 +477,9 @@ class PtrHash {
cpp::span<uint64_t>(hashes).subspan(part_starts[part_in_shard],
part_starts[part_in_shard + 1] -
part_starts[part_in_shard]),
- cpp::span<uint8_t>(
- const_cast<uint8_t *>(pilots.data() + target_pilots_begin),
- target_pilots_end - target_pilots_begin),
+ cpp::span<uint8_t>(const_cast<uint8_t *>(pilot_values.data() +
+ target_pilots_begin),
+ target_pilots_end - target_pilots_begin),
taken[taken_idx]);
if (!total_evictions) {
return false;
@@ -492,7 +492,8 @@ class PtrHash {
}
LIBC_INLINE constexpr cpp::optional<size_t>
- build_part(size_t part, cpp::span<uint64_t> hashes, cpp::span<uint8_t> pilots,
+ build_part(size_t part, cpp::span<uint64_t> hashes,
+ cpp::span<uint8_t> pilot_values,
cpp::array<bool, slots_> &taken) const {
cpp::tuple<cpp::array<uint32_t, buckets_ + 1>,
cpp::array<uint32_t, buckets_>>
@@ -546,7 +547,7 @@ class PtrHash {
const auto new_bucket =
hashes.subspan(starts[new_b], starts[new_b + 1] - starts[new_b]);
if (new_bucket.empty()) {
- pilots[new_b] = 0;
+ pilot_values[new_b] = 0;
continue;
}
const size_t new_b_len = new_bucket.size();
@@ -573,11 +574,11 @@ class PtrHash {
hashes.subspan(starts[b], starts[b + 1] - starts[b]);
if (auto fpilot = this->find_pilot(KMAX, bucket, taken)) {
auto &[p, hp] = fpilot.value();
- pilots[b] = static_cast<uint8_t>(p);
+ pilot_values[b] = static_cast<uint8_t>(p);
for (auto &item :
hashes.subspan(starts[b], starts[b + 1] - starts[b])) {
- auto p = this->slot_in_part_hp(item, hp);
- slots[p] = b;
+ auto item_slot = this->slot_in_part_hp(item, hp);
+ slots[item_slot] = b;
}
continue;
}
@@ -592,8 +593,8 @@ class PtrHash {
size_t collision_score = 0;
for (auto &item :
hashes.subspan(starts[b], starts[b + 1] - starts[b])) {
- auto p = this->slot_in_part_hp(item, hp);
- const auto s = slots[p];
+ auto item_slot = this->slot_in_part_hp(item, hp);
+ const auto s = slots[item_slot];
size_t new_score = 0;
if (s == BUCKET_IDX_NONE) {
continue;
@@ -630,7 +631,7 @@ class PtrHash {
}
const auto &p = cpp::get<1>(best);
- pilots[b] = static_cast<uint8_t>(p);
+ pilot_values[b] = static_cast<uint8_t>(p);
const auto hp = this->hash_pilot(p);
for (auto &item :
hashes.subspan(starts[b], starts[b + 1] - starts[b])) {
@@ -641,10 +642,11 @@ class PtrHash {
heap.push({bucket_len(b2), b2});
evictions++;
- auto hp = this->hash_pilot(static_cast<uint64_t>(pilots[b2]));
- for (auto &item :
+ auto evicted_hp =
+ this->hash_pilot(static_cast<uint64_t>(pilot_values[b2]));
+ for (auto &evicted_item :
hashes.subspan(starts[b2], starts[b2 + 1] - starts[b2])) {
- auto p2 = this->slot_in_part_hp(item, hp);
+ auto p2 = this->slot_in_part_hp(evicted_item, evicted_hp);
slots[p2] = BUCKET_IDX_NONE;
taken[p2] = false;
}
@@ -703,8 +705,8 @@ class PtrHash {
size_t hx = bucket[i];
const auto slot = this->slot_in_part_hp(hx, hp);
if (taken[slot]) {
- for (auto hx : bucket.subspan(0, i)) {
- taken[this->slot_in_part_hp(hx, hp)] = false;
+ for (auto prior : bucket.subspan(0, i)) {
+ taken[this->slot_in_part_hp(prior, hp)] = false;
}
return false;
}
``````````
</details>
https://github.com/llvm/llvm-project/pull/236585
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