Cross 编译

  nightly rustc 的 --print target-list:332 个目标;host = aarch64-apple-darwin
  aarch64-apple-darwin:
    llvm-target          arm64-apple-macosx
    arch                 aarch64
    os                   macos
    data-layout          e-m:o-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-n32:64-S128-Fn32
    linker-flavor        darwin-cc
    max-atomic-width     128
  x86_64-unknown-linux-musl:
    llvm-target          x86_64-unknown-linux-musl
    arch                 x86_64
    os                   linux
    data-layout          e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-i128:128-f80:128-n8:16:32:64-S128
    linker-flavor        gnu-cc
    crt-static-default   True
    max-atomic-width     64
  wasm32-unknown-unknown:
    llvm-target          wasm32-unknown-unknown
    arch                 wasm32
    os                   unknown
    data-layout          e-m:e-p:32:32-p10:8:8-p20:8:8-i64:64-i128:128-n32:64-S128-ni:1:10:20
    linker-flavor        wasm-lld
    max-atomic-width     64
    panic-strategy       abort
  --print cfg(三个目标的 cfg,选 target_arch / target_os / target_pointer_width / target_endian):
    aarch64-apple-darwin         {'target_arch': 'aarch64', 'target_os': 'macos', 'target_pointer_width': '64', 'target_endian': 'little'}
    x86_64-unknown-linux-musl    {'target_arch': 'x86_64', 'target_os': 'linux', 'target_pointer_width': '64', 'target_endian': 'little'}
    wasm32-unknown-unknown       {'target_arch': 'wasm32', 'target_os': 'unknown', 'target_pointer_width': '32', 'target_endian': 'little'}
    aarch64-apple-ios            {'target_arch': 'aarch64', 'target_os': 'ios', 'target_pointer_width': '64', 'target_endian': 'little'}

  退出码 101
       Compiling u169b v0.1.0 (<实验目录>/proj/u169b)
    error[E0463]: can't find crate for `std`
      |
      = note: the `aarch64-apple-ios` target may not be installed
      = help: consider downloading the target with `rustup target add aarch64-apple-ios`
    
    For more information about this error, try `rustc --explain E0463`.
    error: could not compile `u169b` (bin "u169b") due to 1 previous error

  cargo build --target x86_64-apple-darwin:退出码 0
    warning: u169p@0.1.0: build.rs 在 HOST=aarch64-apple-darwin 上运行(它自己的 arch=aarch64),为 TARGET=x86_64-apple-darwin 编译
  file: Mach-O 64-bit executable x86_64
  直接运行:退出码 -1  OSError [Errno 86] Bad CPU type in executable
  用 arch -x86_64 运行:退出码 1  arch: posix_spawnp: <实验目录> Bad CPU type in executable  (本机没有 Rosetta)

  (无 --target)               warning: u169p@0.1.0: build.rs 在 HOST=aarch64-apple-darwin 上运行(它自己的 arch=aarch64),为 TARGET=aarch64-apple-darwin 编译
  x86_64-apple-darwin        warning: u169p@0.1.0: build.rs 在 HOST=aarch64-apple-darwin 上运行(它自己的 arch=aarch64),为 TARGET=x86_64-apple-darwin 编译
  wasm32-unknown-unknown     warning: u169p@0.1.0: build.rs 在 HOST=aarch64-apple-darwin 上运行(它自己的 arch=aarch64),为 TARGET=wasm32-unknown-unknown 编译
  target/ 下的目录:无 --target 时 ['debug'];再加 --target x86_64-apple-darwin 后 ['debug', 'x86_64-apple-darwin'](带 --target 的产物放在以三元组命名的子目录里,宿主的产物仍在 debug/)

  退出码 0
  u169p.wasm:368 字节;file: WebAssembly (wasm) binary module version 0x1 (MVP)
  node 调用:
    exports: add,pointer_bits
    add(2,3) = 5
    pointer_bits() = 32

  默认链接器(本机 cc):退出码 101
    error: linking with `cc` failed: exit status: 1
      = note: ld: unknown options: --as-needed -Bstatic -Bdynamic --eh-frame-hdr -z --gc-sections -z -z
              clang: error: linker command failed with exit code 1 (use -v to see invocation)
    error: could not compile `u169p` (bin "u169p") due to 1 previous error
  换成 zig cc 当链接器(只设 linker):退出码 101
    error: linking with `<实验目录>/zigw/zcc-x86_64` failed: exit status: 1
    ld.lld: error: duplicate symbol: _start
    ld.lld: error: duplicate symbol: _start_c
    error: could not compile `u169p` (bin "u169p") due to 1 previous error
  aarch64 目标,zig 链接器不做任何参数过滤:退出码 101
    = note: error: unsupported linker arg: --fix-cortex-a53-843419
  (给 aarch64 的包装脚本加一行,过滤掉这个参数后再试:)
  x86_64-unknown-linux-musl(linker = zig cc -target x86_64-linux-musl,RUSTFLAGS = -C link-self-contained=no):退出码 0
    file: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), statically linked, stripped
    大小 361 KiB;ELF e_machine = 62(x86-64);程序头里是否有 PT_INTERP(动态链接器):False
    在 macOS 上直接运行:退出码 -1,OSError [Errno 8] Exec format error
  aarch64-unknown-linux-musl(linker = zig cc -target aarch64-linux-musl,RUSTFLAGS = -C link-self-contained=no):退出码 0
    file: ELF 64-bit LSB executable, ARM aarch64, version 1 (SYSV), statically linked, stripped
    大小 345 KiB;ELF e_machine = 183(AArch64);程序头里是否有 PT_INTERP(动态链接器):False
    在 macOS 上直接运行:退出码 -1,OSError [Errno 8] Exec format error

  退出码 0
    warning: u169p@0.1.0: build.rs 在 HOST=aarch64-apple-darwin 上运行(它自己的 arch=aarch64),为 TARGET=aarch64-apple-ios 编译
  file: Mach-O 64-bit executable arm64
  otool -l:加载命令 LC_VERSION_MIN_IPHONEOS,version = 10.0,sdk = 27.0
  对比本机构建:platform = 1,minos = 11.0(platform 1 = macOS)
  在 macOS 上直接运行:退出码 -9 

  本机 aarch64-apple-darwin 运行: os=macos arch=aarch64 pointer=64bit endian=little
  wasm32-unknown-unknown:pointer_bits() = 32 (cfg 里 target_pointer_width = 32)