Generated-code allocator correctness

[sqt]

Motivation

Several C-ABI code paths generated by the Zig and C++ backends hardcoded a fixed allocator (std.heap.c_allocator, plain new/std::unordered_map) instead of routing through the allocator an application actually configured (zzdds_create_factory_with_allocator, zidl_cdr_set_allocator). Under a real custom allocator — exactly what embedded/real-time consumers need — this caused genuine crashes (free(): invalid pointer, operator new() aborts). Found and fixed four confirmed, previously-undetected instances of this bug class during a broader design review of generated-type lifecycle and allocator sourcing.

Description of changes

• New get_allocator vtable slot (mirrors the existing get_c_abi_handle slot) lets a generated C-ABI operation wrapper resolve the producing entity's own allocator instead of guessing at a process-wide default — fixes native-temporary-buffer frees for entity-sequence-returning operations (WaitSet::wait(), Subscriber::get_datareaders(), etc.) and an operation's own by-value return path.
• New zidl_cdr_get_allocator() getter (paired with the existing setter) lets frees with no entity in scope — standalone sequence typedefs, C-ABI struct mirrors used for QoS/config types — route through the process-wide registered allocator instead of a hardcoded default.
• Fixed the C++ backend's shared entity identity-cache (_familyCache) to use std::pmr::unordered_map, matching the already-pmr-routed values it stores.
• New --audit-lifecycle diagnostic flag: classifies every operation's heap-owning output as entity-mediated vs. standalone, flagging ambiguous cases for human review — used to sweep dcps.idl/zzdds.idl for further instances of this bug class.
• New permanent regression test scanning the Zig backend's own source for any reintroduced hardcoded-allocator pattern.

[greptile-apps]

Greptile Summary

The PR routes generated C-ABI lifecycle allocations through their configured allocator while preserving dependency-free Zig C-API generation by making native CDR allocator lookup opt-in.

• Adds the native CDR allocator getter and entity-vtable allocator access.
• Uses allocator-aware storage for generated C++ family identity caches.
• Adds lifecycle auditing and allocator-regression coverage.
• Gates the new zidl_cdr_get_allocator link dependency behind --zig-generate-c-api-cdr-allocator.

Confidence Score: 5/5

The PR appears safe to merge.

No blocking failure remains; the previously reported native CDR link dependency is now isolated behind an explicit opt-in flag, and ordinary Zig C-API generation emits no reference to that external symbol.

Important Files Changed

Filename	Overview
src/backend/zig.zig	Routes generated C-ABI allocations and frees through entity or standalone allocator helpers, with the native CDR dependency correctly gated behind an explicit option.
src/backend/interface.zig	Adds the opt-in Zig C-API CDR allocator option and documents its native-library dependency.
src/main.zig	Parses and forwards the allocator-routing and lifecycle-audit options into backend generation.
packages/zidl-cdr/include/zidl_cdr.h	Exposes the currently registered process-wide allocator through the native CDR API.
packages/zidl-cdr/src/zidl_cdr.c	Implements the allocator getter consistently with the existing process-wide registration.
src/backend/cpp.zig	Changes shared entity-family identity caches to PMR-backed unordered maps so container allocations use the configured C++ resource.
src/backend/lifecycle_audit.zig	Adds diagnostic classification for generated heap-owning operation outputs.

Flowchart

%%{init: {'theme': 'neutral'}}%%
flowchart TD
    A[Generated C-ABI allocation or free] --> B{Entity allocator available?}
    B -- Yes --> C[Resolve allocator through entity vtable]
    B -- No --> D{CDR allocator option enabled?}
    D -- Yes --> E[zidl_cdr_get_allocator]
    D -- No --> F[std.heap.c_allocator fallback]
    E --> G[Registered process-wide allocator or libc fallback]
    C --> H[Matching allocation lifecycle]
    F --> H
    G --> H

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_{Reviews (2): Last reviewed commit: "resolving review comments" | Re-trigger Greptile}

[codecov]

Codecov Report

❌ Patch coverage is 95.72193% with 8 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
src/backend/lifecycle_audit.zig	96.42%	4 Missing ⚠️
packages/zidl-cdr/src/zidl_cdr.c	0.00%	2 Missing ⚠️
src/backend/zig.zig	96.82%	2 Missing ⚠️

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