Pass wrapper.h to bindgen in-memory to avoid rebuild loop#90
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jaredhoberock wants to merge 1 commit intomlir-rs:mainfrom
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Pass wrapper.h to bindgen in-memory to avoid rebuild loop#90jaredhoberock wants to merge 1 commit intomlir-rs:mainfrom
jaredhoberock wants to merge 1 commit intomlir-rs:mainfrom
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Previously the build script wrote `wrapper.h` to `$OUT_DIR` and passed
the path to bindgen via `.header(...)`. Bindgen's `CargoCallbacks` then
emitted `cargo:rerun-if-changed=<wrapper.h path>`, telling cargo to
track the file. Since the build script unconditionally rewrote
`wrapper.h` on every invocation (newer mtime than the script's
`output` file, which is finalized when cargo captures the script's
stdout), cargo always saw the file as newer than its recorded
fingerprint and marked the build script as stale. This forced a
rerun on every `cargo build` / `cargo test`, which in turn
invalidated `mlir-sys`'s lib target and every downstream crate.
Switch to `bindgen::Builder::header_contents("wrapper.h", &content)`
so the wrapper exists only in memory. Bindgen still needs a logical
header name for diagnostics; the string `wrapper.h` is passed but
nothing is written to disk, so there is no file for `CargoCallbacks`
to track and the rerun loop is gone.
Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
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Fixes #89.
Switch the build script from writing
$OUT_DIR/wrapper.hand callingbindgen::Builder::header(path)to callingbindgen::Builder::header_contents("wrapper.h", &content). The wrapper exists only in memory, so there's no file for bindgen'sCargoCallbacksto register viarerun-if-changed, and cargo no longer treats the build script as stale on every invocation.The walk over
{includedir}/mlir-c/is unchanged; the helper is renamed fromgenerate_wrapper -> PathBuftogenerate_wrapper_contents -> String.PathBufimport dropped.Verification
Two consecutive
cargo builds on a downstream crate:Full downstream test suite (289 tests) passes.
Assisted by Claude (Anthropic).