当我给出一个特定的目标时，Clang 编译器找不到 C/C++ 标准库，尽管它在没有给出目标的情况下也能工作 [英] Clang compiler couldn't find C/C++ standard libraries when I gave a specific target although it works without giving target

问题描述

我目前在 ubuntu 上使用 clang11 来编译任何 c/c++ 代码并且它工作正常但是当我尝试编译任何代码时(包括 任何标准库)到任何特定目标的汇编代码，例如 x86_64(即使我有 x86_64)riscv 并给出一个标记 --target=x86_64 或 --target=riscv32 我在代码中包含的任何标准库都出错了.一个简单的例子:

I am currently using clang11 on ubuntu to compile any c/c++ code and it works fine but when I tried to compile any code (including any standard library) to assembly code for any specific target like x86_64 (even I have x86_64) riscv with giving a flag that --target=x86_64 or --target=riscv32 I got errors for any standard library that I included in my code. A simple example:

// ex.cpp
#include<iostream>
int main(){
    int a = 5;
    int b = 3;
    std::cout << a - b;
}

不为特定目标提供标志工作正常:

Without giving flag for a spesific target works fine:

clang++-11 -S ex.cpp -o ex.s

使用 --target=riscv32 标志:

clang++-11 --target=riscv32 -S ex.cpp -o ex.s

给出了这个错误:ex.cpp:1:9: 致命错误:找不到iostream"文件

即使我给出了一个特定的目标，也没有标准库也不会出错.

also without standard libraries gives no error even I give a spesific target.

我几天来一直在寻找解决方案，但我找不到任何合适的解决方案，他们中的大多数人说尝试包含 gnu 库和子文件夹，例如 -I/usr/include/x86_64-linux-gnu/c++/ 但它对我不起作用.

I am searching for a solution for days but I couldn't find any proper solution for this problem, most of them says try to include gnu libraries and subfolders like -I/usr/include/x86_64-linux-gnu/c++/ but it doesn't work for me.

请不要说使用 g++ 编译器，为了添加优化我需要 clang.

Please don't say use g++ compiler, for adding an optimization I need clang.

实际上，我正在尝试为 riscv 目标编译我的代码，与 g++ 链接并使用spike 运行(没有区别 --target=... 或 -target ...):

Actually I am trying to compile my codes for riscv target, linking with g++ and running with spike (doesn't differ --target=... or -target ...):

clang++-11 -target riscv32-unknown-elf -march=rv32gc -fno-addrsig -S ex.cpp -o ex.s
~/riscv/bin/riscv32-unknown-elf-g++ ex.s -o ex
~/riscv/riscv-isa-sim/build/spike --isa=RV32GC ~/riscv/riscv-pk/build/pk ex

它在不包含标准库的情况下也能正常工作.现在，我想问一下

And it works fine without include a standard library. Now, I want to ask that

我可以简单地解决这个问题吗?

Can I solve this problem simply?

或

我可以直接从 riscv bin utils 中使用 clang，比如 ~/riscv/bin/riscv32-unknown-elf-clang++(我在网上看到了类似的东西但找不到)添加和为我的 riscv 目录构建一个子模块?

Can I use clang directly from riscv bin utils like ~/riscv/bin/riscv32-unknown-elf-clang++ (I saw something like this on the net but couldn't find) adding and building a submodule to my riscv directory?

正如@NateEldredge 所说，对于 x86_64 目标三元组应该 --target=x86_64-linux-gnu 但对于 riscv 作为目标三元组 riscv32-unknown-elf我仍然有同样的错误.除了 --target=riscv32-unknown-elf 之外，还有其他适合 riscv 的目标标志吗?也许我错过了这一点.

As @NateEldredge said, for x86_64 target triple should --target=x86_64-linux-gnu but for riscv as a target triple riscv32-unknown-elf I still have the same errors. Is there a proper target flag for riscv any other than --target=riscv32-unknown-elf? Maybe I am missing that point.

推荐答案

我通过使用 riscv-gnu-toolchain 在这里构建并详细回答了类似的问题:使用 Clang 为 RISC-V 编译

I solved my problem by linking compilations with riscv-gnu-toolchain built and also answered a similar question here in detailed: Using Clang to compile for RISC-V

我们只需要交叉编译.您也可以在这里查看更多信息:https://github.com/lowRISC/riscv-llvm#how-can-i-build-upstream-llvmclang-and-use-it-to-交叉编译for-a-riscv32-target

Simply we need cross-compilation. Further information you can also look here: https://github.com/lowRISC/riscv-llvm#how-can-i-build-upstream-llvmclang-and-use-it-to-cross-compile-for-a-riscv32-target

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