c - 如何在 alpine 上编译 32 位的 hello world？

Question

给定一个简单的 hello world 代码:

#include <stdio.h>
int main(void){
  puts("hello");
  return 0;
}

在 64 位 alpine linux 安装上，我尝试将其编译为 64 位和 32 位。第一个工作正常，但第二个缺少 32 位库:

~ # gcc -Wall hello.c 
~ # gcc -Wall -m32 hello.c 
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../libssp_nonshared.a when searching for -lssp_nonshared
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible //usr/lib/libssp_nonshared.a when searching for -lssp_nonshared
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: cannot find -lssp_nonshared
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/libgcc.a when searching for -lgcc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: cannot find -lgcc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../libgcc_s.so when searching for -lgcc_s
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible //usr/lib/libgcc_s.so when searching for -lgcc_s
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: cannot find -lgcc_s
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../libc.so when searching for -lc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../libc.a when searching for -lc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible //usr/lib/libc.so when searching for -lc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible //usr/lib/libc.a when searching for -lc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: cannot find -lc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/libgcc.a when searching for -lgcc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: cannot find -lgcc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../libgcc_s.so when searching for -lgcc_s
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible //usr/lib/libgcc_s.so when searching for -lgcc_s
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: cannot find -lgcc_s
collect2: error: ld returned 1 exit status

因为我找不到解决这个问题的明显方法，所以我将 32 位版本的 gcc、libgcc 和 musl-dev 提取到本地目录并设置 LIBRARY_PATH:

~ # LIBRARY_PATH=usr/lib/gcc/i586-alpine-linux-musl/5.3.0:usr/lib gcc -Wall -m32 hello.c 
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/libgcc.a when searching for -lgcc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: skipping incompatible /usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/libgcc.a when searching for -lgcc
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: i386:x86-64 architecture of input file `/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/crtbeginS.o' is incompatible with i386 output
/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/bin/ld: i386:x86-64 architecture of input file `/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/crtendS.o' is incompatible with i386 output
collect2: error: ld returned 1 exit status
~ # 

这部分解决了问题，但 gcc 仍会首先尝试 64 位库并查找 64 位 crt 文件。

那么在 alpine linux 上编译 32 位二进制文​​件的正确方法是什么？

---

为了让最后一个问题更清楚，看这个:

~ # LIBRARY_PATH=/tmp gcc --verbose -Wall -m32 hello.c 2>&1|grep LIBRARY_PATH
LIBRARY_PATH=/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/:/tmp/:/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../../x86_64-alpine-linux-musl/lib/:/usr/lib/gcc/x86_64-alpine-linux-musl/5.3.0/../../../:/lib/:/usr/lib/

如果我只设置一些 LIBRARY_PATH，编译器会在内部向它添加其他目录。特别是它还预先设置了“错误的”系统目录，其中包含 64 位库。因此它使用了错误的 crt 库，因此出现了上面的最后一个错误。

我要么需要正确的 alpine 包(而不关心它是如何工作的)，要么我需要了解如何更改 gcc 内部添加的第一个路径。

Answer 1

根据 gcc -v 在 alpine gcc 上编译时没有 multilib 支持:

--disable-multilib

虽然在 debian 上启用了 multilib:

--with-multilib-list=m32,m64,mx32 --enable-multilib

-m32 需要 Multilib 支持才能可靠地工作。因此，alpine 上的默认编译器确实不适合编译 32 位二进制文​​件。