[puneetdixit200]

Rationale

Current main already handles the overflow and negative-length cases reported in GH-49973. This PR adds the remaining regression coverage and preserves the upstream implementation.

What changed

• Exercise the quote_utf8 boundary where doubling the input length fits in int32_t, but adding the two quotes overflows.
• Check that concat_ws rejects negative lengths in either valid word and rejects a negative separator length, including when all words are null.
• Verify that null words ignore their lengths and a null separator returns null without inspecting input lengths.

Verification

• Four focused GoogleTest cases passed under AddressSanitizer and UndefinedBehaviorSanitizer in a standalone harness using the production function and test bodies, with context and allocator adapters. This is not the full Gandiva test binary.
• Reintroducing the old negative-length handling caused an AddressSanitizer failure; bypassing the quote addition check caused the boundary test to fail.
• Changed lines formatted with clang-format 18.1.8.
• git diff --check origin/main...HEAD passed.

The full Arrow/Gandiva build was not run locally. CI results for the refreshed commit are pending.

GitHub Issue: #49973

AI assistance disclosure

AI assistance was used to inspect the issue, reconcile the branch with current main, add regression tests, run focused validation, and prepare the PR update.

• GitHub Issue: [C++] Fix remaining overflow and negative length handling issues in Gandiva string functions #49973

[Copilot]

Pull request overview

This PR addresses remaining Gandiva string length safety issues (GH-49973) by preventing signed integer overflow during output-size computation and by rejecting negative “valid” input lengths before allocation/copy, with focused regression tests to prevent reintroduction.

Changes:

• Fix potential signed overflow in quote_utf8 and to_hex_binary by using MultiplyWithOverflow before AddWithOverflow for allocation sizing.
• Add explicit negative-length validation and overflow-safe length accumulation for concat_ws_* before allocation/memcpy.
• Add regression tests covering overflow sizing and negative-length handling.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
cpp/src/gandiva/precompiled/string_ops.cc	Adds checked arithmetic for allocation sizing and validates negative lengths in concat_ws to prevent unsafe allocation/copy paths.
cpp/src/gandiva/precompiled/string_ops_test.cc	Adds targeted tests asserting correct error behavior for overflow sizing and negative-length inputs.

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[puneetdixit200]

Rebased this branch on current main (7c9d88028). No code changes beyond the rebase.

Verified locally:

• git diff --check upstream/main...HEAD

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