carbon-lang/proposals/p0175_decision.md

Decision for: C++ interoperability goals

Proposal accepted on 2020-11-24

Affirming:

• austern
• chandlerc
• geoffromer
• gribozavr
• josh11b
• zygoloid

Abstaining:

• noncombatant
• tituswinters

Open questions

All open questions in the document are intended to be answered later after we have more experience.

Rationale

The core team agrees with the mapping of the proposed interoperability goals to the overall Carbon goals as rationale.

Embedding of C++ bridge code inside Carbon code is inspired in part by experience with CUDA and SYCL, where users provided feedback that these were preferred over alternatives such as OpenCL due to the ability to embed bridge code and device kernels in the same source file as host C++ code. It also matches the approach of bridging between C++ and C where bridge code is often embedded as extern "C" within C++ source files.

The non-goals seem appropriately motivated by the non-interoperability priorities, without undermining the effectiveness of the interoperability as a whole.

We agree with ensuring some level of C interoperability in order to effectively interoperate with both some parts of the C++ ecosystem that rely on the C ABI as well as all other languages which target C-based interoperability.