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diagnose comparisons between two arrays (P2865), fix for [GH #370] - #387
mohitmishra786 wants to merge 2 commits into
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…lowed in C++26. [GH edgcpp#370]
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No actionable comments were generated in the recent review.
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| Layer / File(s) | Summary |
|---|---|
Diagnostic check and operator integration src/error_msg.txt, src/expr.c |
The built-in equality and relational operator paths check the original operands for two array types. C++20 and C++23 produce deprecation warnings. C++26 produces errors, except when emulating GCC versions before 15 or Clang versions before 20, which produce warnings. |
Standard and compiler-version coverage tests/tests/changes/GH370*.sft.cpp, tests/tests/changes/.GH370*.rto/*, tests/tests/imported/clang/cpp/SemaCXX/*, src/pending_changes/gh-370-array-comparisons.txt |
Tests cover equality and relational comparisons between arrays, array-to-pointer comparisons, and expected diagnostics across language modes and compiler versions. The pending-change note describes the diagnostic conditions. |
Priority:
Estimated code review effort: 3 (Moderate) | ~20 minutes
Change: Feature
Merge Risk: 
0d4ea
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The implementation is mergeable; the remaining untested combinations are optional coverage improvements rather than demonstrated failures.
Architecture risk: 
0d4ea
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The change affects 2 systems.
Changed systems:
tests,srcArchitecture concerns
No architecture-level concerns identified.Review details
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Systems and components
- observed — tests (service) was modified; 18 changed files map to changed impact.
- observed — src (service) was modified; 3 changed files map to changed impact.
Before / after behavior
- observed — Modified behavior in src/error_msg.txt: Added diagnostic entries for deprecated and disallowed comparisons between two arrays.
- observed — Modified behavior in src/expr.c: Added
check_for_array_comparison, which checks for two array-typed operands in C++20 mode and diagnoses the comparison. In C++26 mode, it emits an error except on GCC 15+ and Clang 20+, where it emits a deprecation warning. - observed — Modified behavior in src/expr.c: The built-in relational-operator path now checks the original operands for an array comparison before operand transformations.
- observed — Modified behavior in src/expr.c: The built-in equality-operator path now checks the original operands for an array comparison before operand transformations.
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Pre-merge checks: 
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Check name Status Explanation Description Check Check skipped - CodeRabbit’s high-level summary is enabled. Title check The title clearly and concisely describes the main change: diagnosing comparisons between two arrays under P2865, with a reference to the related issue. Linked Issues check Issue #370requires implementing P2865R6, which removes deprecated array comparisons from C++26. The coding requirement is to diagnose comparisons between two arrays using ==, !=, <, <=, >, and >=.
E…Out of Scope Changes check All changed files relate to the array-comparison diagnostic for #370:
- src/expr.c: the new check and its call sites in the relational and equality paths.
- src/error_msg.txt: the two new diagnostic m…Docstring Coverage No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2… Full details: Linked Issues check
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Explanation
Issue
#370requires implementing P2865R6, which removes deprecated array comparisons from C++26. The coding requirement is to diagnose comparisons between two arrays using ==, !=, <, <=, >, and >=.Evidence from the whole-PR summary (merge base 35b7c47 to head 0d4eabd):
- src/expr.c adds check_for_array_comparison. It runs in the built-in paths of process_eq_operator and process_rel_operator, before array-to-pointer conversion. When both operands have array type, C++20 and C++23 produce a deprecation warning. C++26 produces an error.
- src/error_msg.txt adds ec_array_comparison_deprecated and ec_array_comparison_not_allowed.
- Test fixtures under tests/tests/changes/.GH370* and GH370*.sft.cpp cover ==, !=, <, and >= between arrays. They expect warnings in C++20, errors in C++26, and no diagnostic for array-to-pointer comparisons.
- Test fixtures show GNU 150000 (GCC 15) and Clang 200000 with C++26 producing errors. Clang 190000 with C++26 produces warnings. This matches the PR description.
The raw summary says C++26 errors apply unless the compiler is GCC 15 or later or Clang 20 or later. That wording conflicts with the PR description and the fixtures, which both place the warning-only exception before GCC 15 and Clang 20. The fixtures support the PR description. This conflict affects only the emulation exception. It does not affect the core C++26 error or C++20 and C++23 warning requirements.
No incremental diff from d5a1e7d was available. This assessment uses the whole-PR summary and the existing test evidence. The core requirement is met.
Full details: Out of Scope Changes check
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Explanation
All changed files relate to the array-comparison diagnostic for
#370:- src/expr.c: the new check and its call sites in the relational and equality paths.
- src/error_msg.txt: the two new diagnostic messages.
- src/pending_changes/[GNATS 27773] C++26: Remove Deprecated Array Comparisons from C++26 (P2865R6) #370-array-comparisons.txt: the required pending-change note.
- tests/tests/changes/.GH370* and GH370*.sft.cpp: regression fixtures for the new diagnostics.
- tests/tests/imported/clang/cpp/SemaCXX/.deprecated.rto, .self-comparison.rto, .warn-array-comparion.rto, and .warn-self-comparisons.rto: updated expected output. These updates record the new deprecation or error text for existing array-to-array comparisons. They follow directly from the new diagnostics.
No unrelated change is evident in the summary. tests/expectations/edg_x86_64/imported.log is in ignored_files and was not inspected. Its exclusion does not affect this verdict.
Full details: Docstring Coverage
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Explanation
No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 2 files. (9 skipped: 9 unsupported.)
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Fixes #370.
A comparison between two arrays with
==,!=,<,<=,>or>=was accepted silently in every mode. It is deprecated in C++20 and not allowed in C++26 (P2865).process_eq_operatorandprocess_rel_operatornow callcheck_for_array_comparisonbefore the array-to-pointer conversion (the same place<=>already rejects two arrays). If both operands have array type:-std=c++26(checked with the gcc:14 and gcc:15 images); Clang implemented P2865 in Clang 20.A comparison between an array and a pointer is not affected.
Summary by CodeRabbit
Bug Fixes