Rust meets Mobile

2022 BazelCon talk about using bazel to build rust libraries for iOS and Android

Transcript

1. Rust meets
   Mobile
   Keith Smiley (he/him)
   Principal Engineer, Lyft
   @SmileyKeith
   

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2. Sharing code on
   mobile
   

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3. Why rust?
   

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4. Rust + bazel
   

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5. rust_library(
   name = "foo",
   srcs = ["foo.rs"],
   )
   swift_library(
   name = "main",
   srcs = ["main.swift"],
   deps = [":foo"],
   )
   ios_application(...)
   Shouldn't this work?
   

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6. --platforms=//:ios_arm64
   

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7. bazel#7260
   

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8. platform_mappings
   

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9. flags:
   --cpu=arm64-v8a
   --crosstool_top=//external:android/crosstool
   //:android_aarch64
   --cpu=ios_arm64
   --apple_platform_type=ios
   //:ios_arm64
   ...
   

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10. Undefined symbols for architecture arm64:
    "___rust_alloc", referenced from:
    ...
    "___rust_alloc_error_handler", referenced from:
    ...
    ...
    rules_rust#1238 / rust#73632
    

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11. Who does the
    linking?
    

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12. How do I use it?
    

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13. #[no_mangle]
    pub extern fn print_something_from_rust() {
    println!("Ferris says hello!");
    }
    #[no_mangle]
    pub extern fn get_a_value_from_rust() -> i32 {
    42
    }
    extern void print_something_from_rust(void);
    extern int32_t get_a_value_from_rust(void);
    

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14. #[no_mangle]
    pub extern "system" fn Java_com_example_androidapp_JniShim_getValue() ->
    i32 {
    get_a_value_from_rust()
    }
    package com.example.androidapp;
    public class JniShim {
    public static native int getValue();
    }
    

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15. dtolnay/cxx
    rust-lang/rust-bindgen
    

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16. Future areas of
    improvement
    

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17. Developer
    Experience
    

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18. Future rust mobile
    support
    

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19. Was it worth it?
    

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20. keith/bazel-rust-mobile-demo
    

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21. - bazel#11454
    - bazel#15041
    - bazel#15248
    - bazel#15462
    - bazel#7260
    - cargo-raze#484
    - cargo-raze#489
    - rules_rust#1186
    - rules_rust#1238
    - rules_rust#1259
    - rules_rust#1271
    - rules_rust#1276
    - rules_rust#1290
    - rules_rust#1304
    - rules_rust#1362
    - rules_rust#1372
    - rules_rust#1401
    - rules_rust#1462
    - rules_rust#1541
    - rules_rust#1545
    - rules_rust#1546
    - rules_rust#1573
    - rules_rust#1576
    - rust#73632
    

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22. Thank you!
    twitter.com/SmileyKeith
    

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