如何为 x86_64-unknown-linux-musl 构建依赖于 curl 的可执行文件

Question

我在 amd64 Debian 机器上，正在尝试构建 x86_64-unknown-linux-musl 可执行文件。我的 Cargo.toml 中有这个：

[dependencies]
curl = "0.4"

当我运行cargo build --target=x86_64-unknown-linux-musl 我得到 这个：

error: failed to run custom build command for `libz-sys v1.0.10`
process didn't exit successfully: `/tmp/foo/target/debug/build/libz-sys-c20da5f29c41e515/build-script-build` (exit code: 101)
--- stdout
OPT_LEVEL = Some("0")
PROFILE = Some("debug")
TARGET = Some("x86_64-unknown-linux-musl")
debug=true opt-level=0
HOST = Some("x86_64-unknown-linux-gnu")
TARGET = Some("x86_64-unknown-linux-musl")
TARGET = Some("x86_64-unknown-linux-musl")
HOST = Some("x86_64-unknown-linux-gnu")
CC_x86_64-unknown-linux-musl = None
CC_x86_64_unknown_linux_musl = None
TARGET_CC = None
CC = None
HOST = Some("x86_64-unknown-linux-gnu")
CROSS_COMPILE = None
TARGET = Some("x86_64-unknown-linux-musl")
HOST = Some("x86_64-unknown-linux-gnu")
CFLAGS_x86_64-unknown-linux-musl = None
CFLAGS_x86_64_unknown_linux_musl = None
TARGET_CFLAGS = None
CFLAGS = None
running: "./configure" "--prefix=/tmp/foo/target/x86_64-unknown-linux-musl/debug/build/libz-sys-e109627694e9981e/out"
Compiler error reporting is too harsh for ./configure (perhaps remove -Werror).
** ./configure aborting.

--- stderr
thread 'main' panicked at 'failed to run successfully: exit code: 1', /home/tshepang/.cargo/registry/src/github.com-1ecc6299db9ec823/libz-sys-1.0.10/build.rs:189

当我重新运行它时：

error: failed to run custom build command for `openssl-sys v0.9.6`
process didn't exit successfully: `/tmp/foo/target/debug/build/openssl-sys-ac9c042b062dad1d/build-script-build` (exit code: 101)
--- stderr
thread 'main' panicked at '

Could not find directory of OpenSSL installation, and this `-sys` crate cannot
proceed without this knowledge. If OpenSSL is installed and this crate had
trouble finding it,  you can set the `OPENSSL_DIR` environment variable for the
compilation process.

If you're in a situation where you think the directory *should* be found
automatically, please open a bug at https://github.com/sfackler/rust-openssl
and include information about your system as well as this message.

    $HOST = x86_64-unknown-linux-gnu
    $TARGET = x86_64-unknown-linux-musl
    openssl-sys = 0.9.6

当我本地构建时一切正常，即cargo build --target=x86_64-unknown-linux-gnu。

四处搜索，我了解到一个环境变量，PKG_CONFIG_ALLOW_CROSS：

PKG_CONFIG_ALLOW_CROSS=true cargo build --target=x86_64-unknown-linux-musl

在这样做的过程中，我还发现我缺少 Debian 软件包 命名为 libcurl4-openssl-dev。

正在运行ldd target/target/x86_64-unknown-linux-musl/debug/foo 表示可执行文件是动态链接的，然后搜索 此外，我了解了另一个环境变量， PKG_CONFIG_ALL_STATIC：

PKG_CONFIG_ALL_STATIC=true PKG_CONFIG_ALLOW_CROSS=true cargo build --target=x86_64-unknown-linux-musl

这揭示了一大堆缺失的部门，所有这些（幸运的是） 有 Debian 依赖项。但是安装所有这些都没有帮助，因为， 最后，我仍然坐在一个不是 静态链接。

Answer 1

curl crate 依赖于（直接或间接）两个 crate libz-sys 和 openssl-sys。 名称以“-sys”结尾的 crate 通常是一组与本地 C 库的 FFI（外部函数接口）绑定。

构建这样的“-sys”板条箱需要链接到本机库。如果您的目标是 x86_64-unknown-linux-musl，那么您必须链接到针对 musl 而不是 glic 构建的本机库。但是，您将在您的发行版的存储库中找到的大多数包都提供了针对 glibc 构建的库。

解决方案是自己构建所需的库，链接到 musl 而不是 glibc。

我无法访问 Debian 安装，但在 Ubuntu 16.04 上，OpenSSL 看起来像这样：

# this package provides the "musl-gcc" wrapper
apt-get install musl-tools 
# you will also need these, if they are not installed yet
apt-get install pkg-config xutils-dev build-essential

# Download and build OpenSSL against musl
VERS=1.0.2j
export CC=musl-gcc
export MUSL_PREFIX=/usr/local/musl
export C_INCLUDE_PATH="$MUSL_PREFIX/include/"
curl -O https://www.openssl.org/source/openssl-$VERS.tar.gz
tar xvzf openssl-$VERS.tar.gz
cd openssl-$VERS

./config --prefix "$MUSL_PREFIX"
make depend
make
sudo make install

export OPENSSL_DIR=/usr/local/musl/
export OPENSSL_STATIC=1

一旦你有一个相同的 libz（我没有尝试构建它），你就应该能够构建你的 crate：

 cargo build --target=x86_64-unknown-linux-musl

生成的二进制文件将位于target/x86_64-unknown-linux-musl/debug/<binary_name>

cross 工具基本上可以做到这一点，但在 Docker 容器中以保持主机清洁。

此构建生成的二进制文件应该是静态链接的，甚至不依赖于 glibc。这也意味着它会更大*，并且如果在其中一个依赖项中发现安全问题，您需要自行升级任何依赖项（尤其是 OpenSSL）。

*您可能希望在已发布的二进制文件上使用strip。

Answer 2

我放弃并最终使用了cross：

cargo install cross
cross build --target=x86_64-unknown-linux-musl

这太简单了，您会在target/x86_64-unknown-linux-musl/debug 中找到可执行文件。