<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/133934>133934</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            How can I cross compile libcxx to system without libstdc++7.1
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          neko-para
      </td>
    </tr>
</table>

<pre>
    I've prepared a sysroot from ubuntu 16.04, which only has libstdc++ 6.
I want to cross compile libcxx, libcxxabi and libunwind, without clang or any executable. But it shows error that libstdc++ must be at least 7.1.
I think that libcxx shouldn't rely on any libstdc++ featurue.

---

cmake command
```
cmake -S ../llvm-project/llvm -DCMAKE_TOOLCHAIN_FILE=../amd64.cmake -DCMAKE_BUILD_TYPE=Release -DLLVM_ENABLE_RUNTIME="libcxx;libcxxabi;libunwind"
```

output
```
-- The C compiler identification is Clang 20.1.1
-- The CXX compiler identification is Clang 20.1.1
-- The ASM compiler identification is Clang with GNU-like command-line
-- Found assembler: /usr/local/opt/llvm/bin/clang
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/local/opt/llvm/bin/clang - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/local/opt/llvm/bin/clang++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Found Python3: /usr/local/Frameworks/Python.framework/Versions/3.13/bin/python3.13 (found suitable version "3.13.2", minimum required is "3.6") found components: Interpreter
-- Performing Test LLVM_LIBSTDCXX_MIN
-- Performing Test LLVM_LIBSTDCXX_MIN - Failed
CMake Error at cmake/modules/CheckCompilerVersion.cmake:88 (message):
  libstdc++ version must be at least 7.1.
Call Stack (most recent call first):
 cmake/config-ix.cmake:15 (include)
  CMakeLists.txt:848 (include)


-- Configuring incomplete, errors occurred!
```

amd64.cmake
```
set(CMAKE_SYSTEM_NAME Linux)
set(CMAKE_SYSTEM_PROCESSOR x86_64)

set(CMAKE_C_COMPILER_TARGET x86_64-linux-gnu)
set(CMAKE_C_COMPILER clang)
set(CMAKE_CXX_COMPILER_TARGET x86_64-linux-gnu)
set(CMAKE_CXX_COMPILER clang++)

set(CMAKE_SYSROOT "/Volumes/T8/sysroot-amd64")
set(CMAKE_LINKER_TYPE LLD)
```

</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJycVl1v4joQ_TXmZZSIOHw-8AAp2UXLRwXsqn1CTjIQXxKb648W_v2VE6CUttrdK_EQ4jPHZ2bsk2Fa851AHJD2iLQfGsyaXKqBwL30DkyxRiKz02BCaPcF4aDwwBRmwECftJLSwFbJEmxihbEQdPxmi9AIXnOe5iBFcYKcaSh4ok2WEjoidAQdnzSHE3hlwoCRkCqpNaSyPPACHTQ9Hh1H_cQSDkxk7p8Vr1xkFT03ubQG0oKJHUgFTJwAj5haw5ICfRhZA9yAzuWrBlRKKjA5M3dCSqsNJAhuAZk20PWDWpvJudhfQ9Lj0VHZIhOEdg0oLE4gRbXre8YtMmOVRcdCmkPP8-qHtGR7dDmWTGTuVad5_l3WvBX4PqFxUbyU3kHJfzA157_gPUSz4Y_xZr1YTKPvw8l8E0-mYxI-VBGszDot_8xyRo5-TqYPm_Xzo0Mt0WXnFqfTX7PNeD4cTceb5c_5ejJz64TSc9XD0bXo9fOl5PROM2kOpTUHa-7eex6sc4To0k4FPENh-JanzHApgGuIqqbRph_4wU3I09PfBw1Xs98HucMC3-Y_vYK_9cAruMCaKJZWZMC0xjIpUJFwCITGVitXfpmygtBYHi7NIDROuCA0rs5ezfCABlPDxe428eFoAlxs5R9AwINMXuREOaZ72EoFr1Lt30f8lTbwQO_54YDZlxLO5xX17xHvNN4Ab9v2ZcqfgX6X9E3M37WkvolfJ_9G_HX6n2De6a3PzOPJ5FKEn8qLFSvRJaMJjWugv728IzT-hUpzKdxq6AfhNYdDzekHIRDa21b7aMsrX4OXOggIpQ7hU3czaQQlF7y0JSj813Jnz1zXmE4F6EPN41KSAoXRTvJEGFQHhQZVndQjqq1UpSvAGrWByi2mk9Fq_RA9PW1mk_mf4sCDmPGiKn40c8Y0rjyYGah8itC4lJkt0KVf9T46t_pcltrOSDjs9VwZStSa7ZDQPgmd98Cd7V7q8pWhR6woYGVYuq_YpHYenqIwkLqVLVfavJFfJKZSbPnO48ermqDt4rlIC5tVapyUKsEp10b75mic5lbvA-zyPYCoIrXKVY8L15ECDbomVp8pDTJNrVKYERp8NN0br79b1GgI7dXuv3percezzXw4G8OUC3usNXwCeVwuovFqtVjCsdfZdFpXsbfYaBMtZo-T6Xi5WQ-X38brM9h5qD16O2E_8r_FwPlWfkA8Pf0f3psouLnvnwpfPa-Wi8UaqksQ_5KFLasTt-4RGp_nF68qaX1N7sKnk_kPp-35cQzT6cN5i5uaN7JBmPXDPmvgIOi2wjZtdXthIx8E_W6rS9tBkAS9Lm773RSTTojtHqPbZsZaDT6gTdputppB0KEdGvp97ITNdpcGnZSydtIirSaWjBe-Mzhfql2Da21xEIRhP2w1CpZgoS8jmxpUU0Nid5q0mkV1FK9xhpsCB9_lK6RMwOTTccuNYfqkDZbX0erdBev6QcOqYpAbc3DeQWhMaLzjJreJn8ryzYjvxpdKtCv5WffLgP4XAAD__4gMTWU">