[llvm-dev] ld.lld ignoring --sysroot (original) (raw)

Ivan Medoedov via llvm-dev llvm-dev at lists.llvm.org
Thu May 14 04:00:50 PDT 2020

Sorry, it's just

ld.lld: error: unknown emulation: elf_x86-64 ld.lld: error: unable to find library -lc

Path to /linuxroot/usr/lib/x86_64-linux-gnu/crtn.o is correct

On Thu, May 14, 2020 at 12:58 PM Ivan Medoedov <ivan.medoedov at gmail.com> wrote:

Thanks for the replies.

Rui, with your command I get ld.lld: error: unknown emulation: elfx86-64 ld.lld: error: unable to find library -lc ld.lld: error: cannot open /linuxroot/usr/lib/x8664-linux-gnu/crtn.o: No such file or directory

> For your case, you need a linker script located under /linuxroot/, which INPUT or GROUP an absolute path. Do you have an example of such linker script? I have no idea how this works. On Thu, May 14, 2020 at 8:06 AM Fangrui Song <maskray at google.com> wrote: On 2020-05-14, Rui Ueyama via llvm-dev wrote: >On Thu, May 14, 2020 at 11:04 AM Ivan Medoedov via llvm-dev <_ _>llvm-dev at lists.llvm.org> wrote: > >> Hello, >> >> I'm trying to compile a Linux hello world executable on macOS. >> >> The first step is simple: >> >> clang -c -target x8664-linux-gnu -c -o hello.o hello.c >> >> But linking results in an error: >> _>> ld.lld --sysroot=/linuxroot/ -o hello -m elfx8664 _ _>> -dynamic-linker /lib64/ld-linux-x86-64.so.2 _ _>> /lib/crt1.o _ _>> /usr/lib/x8664-linux-gnu/crti.o ../hello.o _ _>> /usr/lib/x8664-linux-gnu/libc.so _ >> /usr/lib/x8664-linux-gnu/crtn.o >> >> ld.lld: error: cannot open /lib/crt1.o: No such file or directory >> ld.lld: error: cannot open /usr/lib/x8664-linux-gnu/crti.o: No such file >> or directory >>

You misunderstand GNU ld's --sysroot rule, which is applicable in these two cases: * when a path begins with "=" or "$SYSROOT" * https://www.sourceware.org/binutils/docs/ld/File-Commands.html "In case a sysroot prefix is configured, and the filename starts with the ‘/’ character, and the script being processed was located inside the sysroot prefix, the filename will be looked for in the sysroot prefix." For your case, you need a linker script located under /linuxroot/, which INPUT or GROUP an absolute path. >--sysroot affects some library search paths, but it doesn't affect paths >directly given to the linker. In the above command line, you are directly >specifying object file and so file paths without -l, so the linker looks at >the only given locations. This is an expected behavior. > >I think, unlike some other linkers, --sysroot option isn't very useful for >lld, because lld doesn't have a notion of built-in default search paths. >You always have to specify library search paths by -L option to lld. So why >don't you specify library directories with -L, like this? > >$ ld.lld -o hello -m elfx86-64 -dynamic-linker /lib64/ld-linux-x86-64.so.2 >-L /linuxroot/usr/lib -lc /linuxroot/usr/lib/x8664-linux-gnu/crtn.o > > >> /linuxroot/ contains all the necessary files copied from a Linux machine: >> /linuxroot/lib/crt1.o, /linuxroot/usr/lib/x8664-linux-gnu/crti.o, etc >> >> It works if I use a full path for each file (-dynamic-linker >> /linuxroot/lib64/ld-linux-x86-64.so.2 ...), but the resulting binary >> doesn't work on Linux, because it's dynamically linked to /linuxroot/... >> which is missing on the Linux box. >> >> file hi >> hi: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically >> linked, interpreter /linuxroot/lib64/ld-linux-x86-64.so.2, for GNU/Linux >> 3.2.0, not stripped >> >> The only way I can make it work is to have actual >> /usr/lib/x8664-linux-gnu/crti.o etc on my macOS box, which --sysroot is >> supposed to help avoid. >> >> I'm sure I'm missing something simple here. I've been following the docs, >> but couldn't figure it out on my own. >> >> Thanks! >> >> ________________________ >> LLVM Developers mailing list >> llvm-dev at lists.llvm.org >> https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev >> >______________________ >LLVM Developers mailing list >llvm-dev at lists.llvm.org >https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20200514/546262cc/attachment.html>

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