Allow the library consumer to specify the Android API level #570
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The build.rs script will use the C preprocessor to pull the API level out of C headers by default. But for build systems that wish to control each build step, and rely on remote compilation, this presents problems. Remove the requirement to run the C preprocessor if the API level is specified via `--cfg`: * android_api_at_least_0: No minimum API level is guaranteed. * android_api_at_least_21: The API level will be at least 21.
The 'no_cc' cfg var controls whether cc is used or the env var.
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Code size changes for a hello-world Rust program linked with libstd with backtrace: On platform
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@danakj Sorry for not getting around to this for a bit. I'm feeling a bit thick and now rust-lang/rust is using cc-rs 1.0.90, so where are we in wanting this? |
No problem. In rust-lang/rust#116318 (comment) you noted that the NDK R26 supports API L21 as its minimum, at which point the build-time check here can go away entirely, and we just always do the We saw that Rust was still on NDK R25, and it looks to still be. So if we want to leave Rust on R25 but use the |
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@danakj It looks like rust-lang/rust#120593 will advance, and when that does, you can simply make this the PR that removes the build check. |
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Oh excellent. Thanks! |
The build.rs script will use the C preprocessor to pull the API level out of C headers by default. But for build systems
that wish to control each build step, and rely on remote compilation, this presents problems.
If
--cfg=no_ccis specified, the the C compiler will not be used. Instead the__ANDROID_API__environment variableis used to specify the API level.