文档列表见:Rust 移动端跨平台复杂图形渲染项目开发系列总结(目录)
项目编译前的操作 build.rs
build.rs可实现正常项目编译前的额外操作,比如代码生成、编译所依赖的C/C++库等行为。为了让编程过程更可控,通常需要输出状态表示通过了某一阶段,或遇到什么错误,Cargo支持build.rs编译时输出不同类型的语句,比如info、warning、error等,以下为示例,参考自rustdroid-native。
println!("cargo:warning=Error executing process command <{:?}>: {}", cmd, e);
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调用C/C++编译器编译所依赖的第三方C/C++库
目前我看到比较完整的参考是官方的libstd/build.rs,编译我们业务所需的第三方库的命令几乎都可以从那找到“灵感”,下面贴出完整代码镇宅,关键操作是build_libbacktrace()
,通过cc::Build
实例把需要编译的C/C++代码声明起来,理论上支持正则匹配文件名与路径 。
#![deny(warnings)]
extern crate build_helper;
extern crate cc;
use build_helper::native_lib_boilerplate;
use std::env;
use std::fs::File;
fn main() {
let target = env::var("TARGET").expect("TARGET was not set");
if cfg!(feature = "backtrace") &&
!target.contains("cloudabi") &&
!target.contains("emscripten") &&
!target.contains("msvc") &&
!target.contains("wasm32")
{
let _ = build_libbacktrace(&target);
}
if target.contains("linux") {
if target.contains("android") {
println!("cargo:rustc-link-lib=dl");
println!("cargo:rustc-link-lib=log");
println!("cargo:rustc-link-lib=gcc");
} else if !target.contains("musl") {
println!("cargo:rustc-link-lib=dl");
println!("cargo:rustc-link-lib=rt");
println!("cargo:rustc-link-lib=pthread");
}
} else if target.contains("freebsd") {
println!("cargo:rustc-link-lib=execinfo");
println!("cargo:rustc-link-lib=pthread");
} else if target.contains("dragonfly") || target.contains("bitrig") ||
target.contains("netbsd") || target.contains("openbsd") {
println!("cargo:rustc-link-lib=pthread");
} else if target.contains("solaris") {
println!("cargo:rustc-link-lib=socket");
println!("cargo:rustc-link-lib=posix4");
println!("cargo:rustc-link-lib=pthread");
println!("cargo:rustc-link-lib=resolv");
} else if target.contains("apple-darwin") {
println!("cargo:rustc-link-lib=System");
// res_init and friends require -lresolv on macOS/iOS.
// See #41582 and http://blog.achernya.com/2013/03/os-x-has-silly-libsystem.html
println!("cargo:rustc-link-lib=resolv");
} else if target.contains("apple-ios") {
println!("cargo:rustc-link-lib=System");
println!("cargo:rustc-link-lib=objc");
println!("cargo:rustc-link-lib=framework=Security");
println!("cargo:rustc-link-lib=framework=Foundation");
println!("cargo:rustc-link-lib=resolv");
} else if target.contains("windows") {
println!("cargo:rustc-link-lib=advapi32");
println!("cargo:rustc-link-lib=ws2_32");
println!("cargo:rustc-link-lib=userenv");
println!("cargo:rustc-link-lib=shell32");
} else if target.contains("fuchsia") {
println!("cargo:rustc-link-lib=zircon");
println!("cargo:rustc-link-lib=fdio");
} else if target.contains("cloudabi") {
if cfg!(feature = "backtrace") {
println!("cargo:rustc-link-lib=unwind");
}
println!("cargo:rustc-link-lib=c");
println!("cargo:rustc-link-lib=compiler_rt");
}
}
fn build_libbacktrace(target: &str) -> Result<(), ()> {
let native = native_lib_boilerplate("libbacktrace", "libbacktrace", "backtrace", "")?;
let mut build = cc::Build::new();
build
.flag("-fvisibility=hidden")
.include("../libbacktrace")
.include(&native.out_dir)
.out_dir(&native.out_dir)
.warnings(false)
.file("../libbacktrace/alloc.c")
.file("../libbacktrace/backtrace.c")
.file("../libbacktrace/dwarf.c")
.file("../libbacktrace/fileline.c")
.file("../libbacktrace/posix.c")
.file("../libbacktrace/read.c")
.file("../libbacktrace/sort.c")
.file("../libbacktrace/state.c");
let any_debug = env::var("RUSTC_DEBUGINFO").unwrap_or_default() == "true" ||
env::var("RUSTC_DEBUGINFO_LINES").unwrap_or_default() == "true";
build.debug(any_debug);
if target.contains("darwin") {
build.file("../libbacktrace/macho.c");
} else if target.contains("windows") {
build.file("../libbacktrace/pecoff.c");
} else {
build.file("../libbacktrace/elf.c");
let pointer_width = env::var("CARGO_CFG_TARGET_POINTER_WIDTH").unwrap();
if pointer_width == "64" {
build.define("BACKTRACE_ELF_SIZE", "64");
} else {
build.define("BACKTRACE_ELF_SIZE", "32");
}
}
File::create(native.out_dir.join("backtrace-supported.h")).unwrap();
build.define("BACKTRACE_SUPPORTED", "1");
build.define("BACKTRACE_USES_MALLOC", "1");
build.define("BACKTRACE_SUPPORTS_THREADS", "0");
build.define("BACKTRACE_SUPPORTS_DATA", "0");
File::create(native.out_dir.join("config.h")).unwrap();
if !target.contains("apple-ios") &&
!target.contains("solaris") &&
!target.contains("redox") &&
!target.contains("android") &&
!target.contains("haiku") {
build.define("HAVE_DL_ITERATE_PHDR", "1");
}
build.define("_GNU_SOURCE", "1");
build.define("_LARGE_FILES", "1");
build.compile("backtrace");
Ok(())
}
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条件编译
所有的条件编译都由通过cfg配置实现,cfg支持any、all、not等逻辑谓词组合。
基本用法
在Cargo.toml中添加[features]
段,然后列举需要组合的feature名,大体上相当于gcc -条件1 -条件2 -条件3 ...
。
[features]
default = []
metal = ["gfx-backend-metal"]
vulkan = ["gfx-backend-vulkan"]
dx12 = ["gfx-backend-dx12"]
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mod级别条件编译
实现示例,参考gl_generator.rs
#[cfg(feature = "unstable_generator_utils")]
pub mod generators;
#[cfg(not(feature = "unstable_generator_utils"))]
mod generators;
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编译特定CPU架构
指定target_arch + CPU架构名称字符串,如#[cfg(target_arch= "x86")]
,#[cfg(any(target_arch = "arm", target_arch = "x86"))]
。
#[cfg(any(target_arch = "arm", target_arch = "x86"))]
mod arch {
use os::raw::{c_uint, c_uchar, c_ulonglong, c_longlong, c_ulong};
use os::unix::raw::{uid_t, gid_t};
#[stable(feature = "raw_ext", since = "1.1.0")]
pub type dev_t = u64;
#[stable(feature = "raw_ext", since = "1.1.0")]
pub type mode_t = u32;
#[stable(feature = "raw_ext", since = "1.1.0")]
pub type blkcnt_t = u64;
#[stable(feature = "raw_ext", since = "1.1.0")]
pub type blksize_t = u64;
#[stable(feature = "raw_ext", since = "1.1.0")]
pub type ino_t = u64;
#[stable(feature = "raw_ext", since = "1.1.0")]
pub type nlink_t = u64;
#[stable(feature = "raw_ext", since = "1.1.0")]
pub type off_t = u64;
#[stable(feature = "raw_ext", since = "1.1.0")]
pub type time_t = i64;
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#[doc(include = "os/raw/char.md")]
#[cfg(any(all(target_os = "linux", any(target_arch = "aarch64",
target_arch = "arm",
target_arch = "powerpc",
target_arch = "powerpc64",
target_arch = "s390x")),
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[target.'cfg(any(target_os = "macos", all(target_os = "ios", target_arch = "aarch64")))'.dependencies.gfx-backend-metal]
git = "https://github.com/gfx-rs/gfx"
version = "0.1"
optional = true
[target.'cfg(target_os = "android")'.dependencies.gfx-backend-vulkan]
git = "https://github.com/gfx-rs/gfx"
version = "0.1"
optional = true
#[target.'cfg(windows)'.dependencies.gfx-backend-dx12]
#git = "https://github.com/gfx-rs/gfx"
#version = "0.1"
#optional = true
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编译成指定类型二进制包(.a/.so/.r)
目前还没找到支持编译出macOS/iOS支持的.framework
办法。
在Cargo.toml中添加[lib]
段,
name
表示输出的库名,最终输出文件名为lib+name.a或lib+name.so,比如libportability.so。crate-type
表示输出的二进制包类型,比如staticlib
= .a iOS只认Rust输出.a,Android可以.a和.so,配置成["staticlib", "cdylib"]
在用cargo-lipo时会出警告不支持cdylib
,忽略即可。cdylib
= .sorlib
= 给Rust用的静态库dylib
= 给Rust用的动态库
path
表示库项目的入口文件,通常是src/lib.rs,如果改动了这一位置,可通过path = 新位置实现,比如:
[lib]
name = "portability"
crate-type = ["staticlib", "cdylib"]
path = "src/ios/lib.rs"
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SDK开发的“售后服务”
提供.a/.so给业务团队,这一过程可能会有人为失误导致大家对接失败,下面介绍些我们使用的小技巧。
读取.a静态库的iOS版本
在macOS terminal执行如下命令,用/
查找VERSION
。
otool -lv xyz.a | less
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参考:check-ios-deployment-target-of-a-static-library
nm查看导出符号
有时编码疏忽导致没给需要导出的C接口添加#[no_mangle]
和extern
等修饰,或者使用了不合理的优化attribute导致符号被优化掉,此时业务链接我们的库就会失败,因此,交付二进制包前用nm确认符号表是合格的工程师习惯。以下为示例代码。
nm -D ./target/release/libportability.so | grep fun_call_exported_to_c
0000000000003190 T fun_call_exported_to_c
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