feat(cli): add --relocatable flag to force ET_REL output#83
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feat(cli): add --relocatable flag to force ET_REL output#83
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Currently synth produces a relocatable object (.o, ET_REL) only when the input wasm has imports — the relocations they generate trigger the relocatable code path. Self-contained wasm modules with no imports produce a complete ET_EXEC firmware with vector table, Reset_Handler, linear_memory section, etc. For linking into a host build system (e.g. integrating verified Rust kernel primitives compiled to wasm into a Zephyr build), the host expects a relocatable .o it can pull into its existing link step. Add a --relocatable CLI flag that forces ET_REL output regardless of whether the wasm has imports. The flag is additive — default behaviour is unchanged. Tested with gale-ffi.wasm (200 functions, 0 imports): output is now a 26645-byte ET_REL ARM EABI5 object with all gale_* symbols defined and no vector-table machinery. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Summary
--relocatableflag that forces ET_REL output regardless of whether the wasm has imports — for linking into a host build system that has its own startup code (e.g., integrating verified Rust kernel primitives compiled to wasm into a Zephyr build).Context
This unblocks a follow-up experiment on the gale engine bench: compiling gale-ffi (formally-verified Rust replacement for Zephyr kernel primitives) to wasm32, then using synth to lower the wasm to a Cortex-M4F relocatable .o that links into the existing Zephyr build alongside the C kernel. The rest of the build expects
libgale_ffi.a(which we'll wrap from synth's .o), so synth's output needs to be a relocatable, not a full firmware.Tested with gale-ffi.wasm (200 functions, 0 imports):
--relocatable: 27052-byte ET_EXEC firmware with Reset_Handler, vector table, linear_memory section.--relocatable: 26645-byte ET_REL ARM EABI5 object with all gale_* symbols defined and no firmware machinery.Test plan
cargo checkpassescargo install --path crates/synth-cli --forcesucceeds--relocatable) still produces ET_EXEC — verified withfile output.elf--relocatableproduces ET_REL — verified withfile output.oreporting "ELF 32-bit LSB relocatable, ARM, EABI5"nm