bindgen::ParseCallbacks: support tracking env variable usage for cargo #2400
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☔ The latest upstream changes (presumably 2be14a3) made this pull request unmergeable. Please resolve the merge conflicts. |
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@pvdrz ? |
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Hey! Thanks for the ping, I'll be reviewing this soon. For the time being could you fix the formatting. It seems you're running |
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☔ The latest upstream changes (presumably 040149b) made this pull request unmergeable. Please resolve the merge conflicts. |
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bindgen currently has a `bindgen/build.rs` which attempts to have cargo rebuild bindgen when TARGET specific env variables change, specifically `BINDGEN_EXTRA_CLANG_ARGS_<target>`. Unfortunately, this doesn't have the desired effect in most cases. Specifically, when a crate `A` has `bindgen` in `build-dependencies`, and we're cross compiling `A` for target `T` on a host `H`, `bindgen`'s `build.rs` will observe `TARGET` set to `H` (the host target name) instead of `T` (because `bindgen` itself is being built for `H` and not `T`). Then, within the build script of crate `A`, one would use `bindgen` to generate bindings, and now `TARGET` is set to `T`, so different env variables are used. Allow crates using `bindgen` in build scripts to correctly handle env variable changes by adding `ParseCallbacks::read_env_var()` to track env var reads and adding a basic implementation to `CargoCallbacks` to emit `cargo:rerun-if-env-changed` lines.
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bindgen currently has a
bindgen/build.rswhich attempts to have cargo rebuild bindgen whenTARGETspecific env variables change, specificallyBINDGEN_EXTRA_CLANG_ARGS_<target>. Unfortunately, this doesn't have the desired effect in most cases.Specifically, when a crate
Ahasbindgeninbuild-dependencies, and we're cross compilingAfor targetTon a hostH,bindgen'sbuild.rswill observeTARGETset toH(the host target name) instead ofT(becausebindgenitself is being built forHand notT). Then, within the build script of crateA, one would usebindgento generate bindings, and nowTARGETis set toT, so different env variables are used.Allow crates using
bindgenin build scripts to correctly handle env variable changes by addingParseCallbacks::read_env_var()to track env var reads and adding a basic implimentation toCargoCallbacksto emitcargo:rerun-if-env-changedlines.