DO NOT MERGE: Build against c2pa-rs main (nightly)

[scouten-adobe]

DO NOT MERGE — c2pa-rs main compatibility probe

Build c2pa-c-ffi from source from contentauth/c2pa-rs main to detect incompatibilities ahead of the mid-November breaking-changes release. This remains a draft / DO NOT MERGE experiment.

CI logs the actual Rust commit and toolchain versions. The redundant initial prebuilt-binary configure step has been removed; the existing Makefile configures source builds for debug and sanitizer tests.

Latest compatibility check (2026-10-16)

Checked against contentauth/c2pa-rs commit 60f7cbdc69ab7a2554fcc87eb4df77050814b2cf (0.92.0-dev), confirmed to be main at the time of the check. Local platform: macOS arm64, AppleClang 21, Cargo 1.98.1.

Original result: incompatible. The Rust release library built, but deleted APIs and opaque stream handles prevented C/C++ compilation. Commit c1a0855 addresses those failures, and the complete platform CI matrix now passes.

API migration

User-directed choice: migrate to supported APIs and remove obsolete methods rather than add a compatibility layer.

Former blocker	Resolution
Opaque C2paStream	C++ wrappers use composition; the C test owns its FILE and opaque stream separately.
Deleted c2pa_load_settings	Removed c2pa::load_settings; use explicit Context settings instead. Migrated settings-dependent tests and documentation.
Deleted builder/reader constructors	Existing context-free C++ constructors remain as adapters that create a default Context and call supported APIs. C integration tests use context + with_definition, with_archive, and with_stream.
Deleted data-hashed signing functions	Removed Builder::data_hashed_placeholder and Builder::sign_data_hashed_embeddable. Use a Context signer, placeholder, set_data_hash_exclusions, update_hash_from_stream, and sign_embeddable. The old external precomputed DataHash JSON argument has no drop-in replacement.
Deleted c2pa_format_embeddable	Retained C++ Builder::format_embeddable using c2pa_builder_compose_manifest.
Deleted c2pa_signature_free	Use c2pa_free.

The embeddable tests now embed actual JPEG/PNG placeholders, compute exclusions and hashes, patch the exact-size final manifest, and verify readback. JPEG coverage includes replacement of existing JUMBF, metadata preservation, raw-manifest formatting, and detection of tampering outside exclusions. BoxHash coverage remains.

Also fixed source-build infrastructure: declare/copy generated headers and Windows import libraries, link the C test to the proper import library, initialize MSVC for both Windows architectures, and avoid a prebuilt-only diagnostic test for source builds.

Compatibility notes

This intentionally changes the public C++ API: load_settings and the two old data-hashed signing methods are removed. Context-free constructors no longer read thread-local settings. Pass explicit Context objects for non-default configuration. Stream wrappers no longer inherit from the C ABI stream type; use their existing c_stream member.

Validation

• macOS arm64: library, tests, and examples build against the checked Rust main revision.
• Full debug suite: all 363 C++ tests and the C integration test pass.
• Default released 0.91.0 dependency: library, tests, and examples still compile.
• Full ASan/UBSan suite: all 363 C++ tests and the C integration test pass using AppleClang 21.
• Homebrew LLVM 19's ASan runtime hangs during initialization on this macOS 26.6.2 host, before test code runs (confirmed by process sampling); both test executables hit the 180-second timeout. Rebuilding with the installed AppleClang runtime resolves this local tooling issue.
• CI run 38970848917: all eight platform jobs pass for c1a0855: Windows x64/arm64, macOS arm64/Intel, Ubuntu latest and 22.04 x64, and Ubuntu 22.04/24.04 arm64. Debug suites pass everywhere; sanitizer suites pass on Linux and macOS (skipped on Windows by the existing workflow).

Local reproduction

mkdir -p target
git clone --depth 1 https://github.com/contentauth/c2pa-rs.git target/c2pa-rs
cmake -S . -B build/nightly -G Ninja \
  -DCMAKE_BUILD_TYPE=Debug \
  -DC2PA_BUILD_FROM_SOURCE=ON \
  -DC2PA_RS_PATH="$PWD/target/c2pa-rs"
cmake --build build/nightly
ctest --test-dir build/nightly --output-on-failure

Earlier failed CI runs predate the migration fixes.