GH-50186: [C++][Gandiva] REPLACE throws "Buffer overflow for output string" for results larger than 64 KB #50187
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| // Licensed to the Apache Software Foundation (ASF) under one | ||
| // or more contributor license agreements. See the NOTICE file | ||
| // distributed with this work for additional information | ||
| // regarding copyright ownership. The ASF licenses this file | ||
| // to you under the Apache License, Version 2.0 (the | ||
| // "License"); you may not use this file except in compliance | ||
| // with the License. You may obtain a copy of the License at | ||
| // | ||
| // http://www.apache.org/licenses/LICENSE-2.0 | ||
| // | ||
| // Unless required by applicable law or agreed to in writing, | ||
| // software distributed under the License is distributed on an | ||
| // "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY | ||
| // KIND, either express or implied. See the License for the | ||
| // specific language governing permissions and limitations | ||
| // under the License. | ||
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| // Microbenchmark comparing the current REPLACE implementation against the | ||
| // pre-change one, to measure the cost of the O(n) match-counting scan that the | ||
| // fix added to size the output buffer exactly. | ||
| // | ||
| // new = replace_utf8_utf8_utf8 (counting scan + exact allocation) | ||
| // old = replace_with_max_len_utf8_utf8_utf8(..., capacity, ...) | ||
| // The old wrapper was literally a call to this with a fixed cap of | ||
| // 65535; given a buffer large enough to hold the result it is the | ||
| // pre-change algorithm with no counting scan, so new-vs-old isolates | ||
| // the scan overhead. (The shipped old cap of 65535 additionally errored | ||
| // out for any result above ~64 KB -- the bug this change fixes.) | ||
| // | ||
| // Reported time includes one ExecutionContext::Reset() per call in both arms | ||
| // (it cancels out in the delta), mirroring per-call arena reuse. | ||
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| #include <chrono> | ||
| #include <cinttypes> | ||
| #include <cstdint> | ||
| #include <cstdio> | ||
| #include <functional> | ||
| #include <string> | ||
| #include <vector> | ||
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| #include <gtest/gtest.h> | ||
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| #include "gandiva/execution_context.h" | ||
| #include "gandiva/precompiled/types.h" | ||
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| namespace gandiva { | ||
| namespace { | ||
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| // Builds a `len`-byte string whose `match` byte occurs once every `stride` | ||
| // bytes (the rest filled with `filler`), giving len/stride non-overlapping | ||
| // matches. | ||
| std::string MakeText(int64_t len, int stride, char match, char filler) { | ||
| std::string s(static_cast<size_t>(len), filler); | ||
| for (int64_t i = 0; i < len; i += stride) { | ||
| s[static_cast<size_t>(i)] = match; | ||
| } | ||
| return s; | ||
| } | ||
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| double TimeNsPerCall(const std::function<void()>& fn, int iters) { | ||
| auto t0 = std::chrono::steady_clock::now(); | ||
| for (int i = 0; i < iters; ++i) { | ||
| fn(); | ||
| } | ||
| auto t1 = std::chrono::steady_clock::now(); | ||
| return std::chrono::duration<double, std::nano>(t1 - t0).count() / iters; | ||
| } | ||
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| struct Case { | ||
| std::string name; | ||
| int64_t text_len; | ||
| int stride; // a match every `stride` bytes | ||
| std::string from; | ||
| std::string to; | ||
| int iters; | ||
| }; | ||
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| } // namespace | ||
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| TEST(StringOpsBenchmark, Replace) { | ||
| ExecutionContext ctx; | ||
| int64_t ctx_ptr = reinterpret_cast<int64_t>(&ctx); | ||
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| const int64_t kSmall = 256; | ||
| const int64_t kMedium = 64 * 1024; | ||
| const int64_t kLarge = 4 * 1024 * 1024; | ||
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| std::vector<Case> cases = { | ||
| // Expansion cases (to longer than from) -- these take the O(n) scan path. | ||
| {"small/dense expand a->ab", kSmall, 1, "a", "ab", 200000}, | ||
| {"small/sparse expand a->ab", kSmall, 64, "a", "ab", 200000}, | ||
| {"medium/dense expand a->ab", kMedium, 1, "a", "ab", 4000}, | ||
| {"medium/sparse expand a->ab", kMedium, 64, "a", "ab", 4000}, | ||
| {"large/dense expand a->ab", kLarge, 1, "a", "ab", 80}, | ||
| {"large/sparse expand a->ab", kLarge, 64, "a", "ab", 80}, | ||
| // Big-expansion cases (to_len - from_len > from_len) -- these fall back to | ||
| // the exact match-counting scan, so new should still show the scan delta. | ||
| {"large/dense bigexp a->abcd", kLarge, 1, "a", "abcd", 80}, | ||
| {"large/sparse bigexp a->abcd", kLarge, 64, "a", "abcd", 80}, | ||
| // Shrink case (to no longer than from) -- new skips the scan entirely. | ||
| {"large/dense shrink ab->a", kLarge, 2, "ab", "a", 80}, | ||
| }; | ||
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| printf("\n%-28s %10s %9s %12s %12s %9s\n", "case", "text_len", "matches", "new ns/call", | ||
| "old ns/call", "delta"); | ||
| printf("%s\n", std::string(92, '-').c_str()); | ||
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| for (const auto& c : cases) { | ||
| std::string text = MakeText(c.text_len, c.stride, c.from[0], 'x'); | ||
| const char* tp = text.data(); | ||
| auto tlen = static_cast<int32_t>(text.size()); | ||
| const char* fp = c.from.data(); | ||
| auto flen = static_cast<int32_t>(c.from.size()); | ||
| const char* op = c.to.data(); | ||
| auto olen = static_cast<int32_t>(c.to.size()); | ||
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| // Count matches and compute the exact output size to give the "old" arm a | ||
| // buffer large enough to complete (precomputed -- not part of the timing). | ||
| int64_t matches = 0; | ||
| if (flen > 0 && flen <= tlen) { | ||
| for (int32_t i = 0; i <= tlen - flen;) { | ||
| if (memcmp(tp + i, fp, flen) == 0) { | ||
| ++matches; | ||
| i += flen; | ||
| } else { | ||
| ++i; | ||
| } | ||
| } | ||
| } | ||
| auto out_capacity = static_cast<int32_t>(tlen + matches * (olen - flen)); | ||
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| auto run_new = [&]() { | ||
| int32_t out_len = 0; | ||
| replace_utf8_utf8_utf8(ctx_ptr, tp, tlen, fp, flen, op, olen, &out_len); | ||
| ctx.Reset(); | ||
| }; | ||
| auto run_old = [&]() { | ||
| int32_t out_len = 0; | ||
| replace_with_max_len_utf8_utf8_utf8(ctx_ptr, tp, tlen, fp, flen, op, olen, | ||
| out_capacity, &out_len); | ||
| ctx.Reset(); | ||
| }; | ||
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| // Warm up (and verify both produce the same length / no error). | ||
| run_new(); | ||
| ASSERT_FALSE(ctx.has_error()); | ||
|
Contributor
There was a problem hiding this comment. you are resetting context in lambdas so this assert is asserting what exactly? |
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| run_old(); | ||
| ASSERT_FALSE(ctx.has_error()); | ||
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| double new_ns = TimeNsPerCall(run_new, c.iters); | ||
| double old_ns = TimeNsPerCall(run_old, c.iters); | ||
| double delta = old_ns > 0 ? (new_ns - old_ns) / old_ns * 100.0 : 0.0; | ||
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| printf("%-28s %10" PRId64 " %9" PRId64 " %12.1f %12.1f %+8.1f%%\n", c.name.c_str(), | ||
| c.text_len, matches, new_ns, old_ns, delta); | ||
| } | ||
| printf("\n"); | ||
| } | ||
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| } // namespace gandiva | ||
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Did you mean to add this? It would seems such an addition would make benchmark a regular test, NOT on demand.