Experimental scalar C11 emitter — v0.0.5-alpha.5
This functionality shipped in the official alpha.5 compiler prerelease at source commit 2eeed0aa52ccb59523307841ad8ffbd83f8911a8. It is a Rust embedding API only. There is no scarp compile CLI command, no native Scarp executable output, and no stable ABI.
API for Rust embedding hosts
The tagged Rust library exports scarp::c_backend::emit_c(source: &str) and emit_program(&ResolvedProgram). The return value is a complete freestanding C11 translation-unit string, or a diagnostic. The emitter does not write output files, invoke a C compiler or linker, or access a registry.
A Rust embedding host can request generated C text:
let c_source = scarp::c_backend::emit_c(
"var total = 0; repeat 4 as n { total += n; } print(total);"
)?;
The host must separately select and supply a C11 compiler to compile that text. This is a Rust API illustration, not a Scarp CLI example. The complete interpreter-verifiable program is in the published alpha.5 guide.
Exactly which features are supported?
| Experimental C backend accepts | C backend rejects |
|---|---|
| Scalar integer and boolean values, checked arithmetic and bit operations, comparison and short-circuit boolean logic | Floats, vectors, numerical tiles, user functions, recursion |
| bind and var scalar slots, updates, if, while, repeat COUNT as index, nested loops, break and continue | Unsupported imports, computed string construction, dynamic collections |
| Single-argument stdout print/println for scalar expressions or literal UTF-8 text | Multi-argument output, stderr, write and unsupported intrinsics |
Unsupported C emission uses E0049. Invalid shifts use E0046; negative repeat counts use E0019. These are restrictions on the C backend; they do not remove features from the interpreter.
The emitter caps each program at 256 scalar slots, 4096 operations, 1024 expression nodes per expression, 16384 total nodes, and 65536 bytes of literal string payload. The generated freestanding C11 unit offers caller-owned struct scarp_workspace and struct scarp_host. It supports work/print budgets only, not all interpreter ExecutionOptions.
The generated scarp_validate checks execution without writing output. scarp_run validates before replaying output to a synchronous host callback. A callback failure may leave earlier output bytes written. Host tooling, ABI stability, memory isolation, compilation and linking are outside this API's guarantees.
Source-backed evidence
The exact published files are src/c_backend.rs, tests/c_backend.rs and Proposal 0035. The compiler release CI tested interpreter/C differential behavior and build restrictions. This page does not claim a general-purpose native compiler.
See the alpha.5 release notes, alpha.5 CLI and feature status.