[thirtytwobits]

Adds std::vector::insert to cetl::VariableLengthArray. All five overloads are included, for both the general and the packed-bool versions:

iterator insert(const_iterator pos, const T& value);
iterator insert(const_iterator pos, T&& value);
iterator insert(const_iterator pos, size_type count, const T& value);
template <class InputIt> iterator insert(const_iterator pos, InputIt first, InputIt last);
iterator insert(const_iterator pos, std::initializer_list<T> ilist);

These cover the range and initializer-list forms requested in the issue comments. Each returns an iterator to the first inserted element, or to pos if nothing was inserted.

How it works

New elements are constructed at the end of the array, then std::rotate moves them into place.

• This needs only what the standard requires of insert: elements must be MoveAssignable and Swappable. Elements are only constructed from a range's *first, never assigned from it, so a type that is constructible but not assignable from the source works. (The bool specialization rotates through the proxy swap added in Add reverse iterators to VariableLengthArray (#65); move CI to toolshed ts26.4.5 #244.)
• Capacity grows geometrically, as for push_back(), so repeated insertion stays amortized. Forward ranges are measured and reserved once; single-pass ranges are appended one element at a time.

Guarantees

Situation	Result
Constructing a new element throws, or a single-pass source's read or advance throws	The new elements are destroyed and the array is unchanged, except that capacity may stay grown (as with resize())
Moving existing elements throws during the rotation	Every element stays alive and counted; their order is unspecified
insert(pos, v[i]) or insert(pos, n, v[i]), even when inserting reallocates	Correct: an aliased value is copied first
Exceptions disabled; a sized insertion exceeds max_size() or the allocator declines	No effect; detect it with size()
Exceptions disabled; a single-pass range doesn't fit	The prefix that fit is kept, as assign(first, last) does

New debug assertions reject positions outside the array: CDE_vla_013, and CDE_vla_014 for bool, which also rejects another array's iterator.

Tests

• New test_variable_length_array_insert.cpp, typed over int and bool and checked against std::vector:
  • every position in arrays of 0, 1, 7, 8, 9 and 17 elements (crossing packed-byte boundaries), for each overload and several counts, including random-access, forward, single-pass and initializer-list sources
  • mutable iterator positions, and empty insertions on a never-allocated array
  • geometric growth, and max_size() with and without exceptions
  • overload resolution (insert(pos, 3, 4) and insert(pos, {5}))
  • an aliased value, with and without reallocation
  • move-only elements, and elements that are constructible but not assignable from the source
  • no allocation when capacity suffices, declined growth, and narrowing conversions under -Wconversion -Werror
• Exception safety:
  • failures while constructing, reading or advancing leave the array unchanged
  • rotation failures keep every element alive
  • allocation failure changes nothing
  • a bool conversion failure restores the bits
• Death tests: for both new assertions.
• Fuzzer: the emplace_back operation now also chooses among the insert overloads from its spare opcode bits, so the input format is unchanged, and checks each returned position.

Found along the way

• libc++ bug: libc++ 23's own std::vector<bool>::insert has undefined behaviour. It shifts a word by its full width in __copy_backward_unaligned, which UBSan reports. I reproduced it with plain std::vector<bool> and no CETL code. The fuzzer's reference model therefore rebuilds itself instead of calling std::vector::insert.
• CETL bug, filed separately as VLA push_back/emplace_back store a wrong value when the argument is an element of the array and storage must grow #245: push_back(v[0]) and emplace_back(v[0]) store the wrong value when they have to grow the storage. insert doesn't have this problem.

Validation

• GCC 13, C++14: all 16 VLA test suites pass in Debug and DebugEP (-fno-exceptions)
• GCC 7 (toolshed ts24.4.3): the insert and exception-safety suites pass with and without exceptions
• toolshed ts26.4.3: the insert and exception-safety suites compile cleanly with GCC 15 (C++14, C++20) and Clang 22 (C++23, libc++)
• Clang, C++20, ASan + UBSan (with pointer-overflow checking): the insert and exception-safety suites pass
• GCC 13 and Clang, C++14/17/20/23, with and without exceptions: the insert, exception-safety, debug-assert and bool suites compile cleanly with -Wall -Wextra -Werror -Wconversion -Wsign-conversion -Wfloat-equal -pedantic
• libFuzzer, default and embedded profiles: ctest passes, plus 90 s runs of about 850k–900k inputs each with no findings
• Header formatting: clang-format 19.1.7 (ts24.4.3) and 22.1.2 (ts26.4.3) both report no changes; git diff --check is clean

Closes #62.

🤖 Generated with Claude Code

[thirtytwobits]

@codex review

[chatgpt-codex-connector]

Codex Review Summary

This comment shows the latest Codex review activity on this pull request.

Review	Status	Commit	Review trigger
📝 Code Review	✅ Completed 2026-10-19T22:31:52.438497Z	460719d	Manual request

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review" or "@codex security review".

Codex reacts with 👀 while any review is running, comments if it has suggestions, and reacts with 👍 once all reviews finish with no findings.

[thirtytwobits]

@codex review

[chatgpt-codex-connector]

Codex Review: Didn't find any major issues. Already looking forward to the next diff.

Reviewed commit: 460719d3ba

ℹ️ About Codex in GitHub

Your team has set up Codex to review pull requests in this repo. Reviews are triggered when you

• Open a pull request for review
• Mark a draft as ready
• Comment "@codex review".

If Codex has suggestions, it will comment; otherwise it will react with 👍.

Codex can also answer questions or update the PR. Try commenting "@codex address that feedback".