<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/57898>57898</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            apt.llvm.org clang-15 is not able to compile with C++17 feature std::execution::par
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          cguentherTUChemnitz
      </td>
    </tr>
</table>

<pre>
    Steps to reproduce:

Ubuntu with clang from **apt.llvm.org** and with potential pstl backends installed via libtbb2-dev and clang-15-openmp is not able to compile with C++17 feature std::execution::par.

Dockerfile:
```
FROM ubuntu:22.04

RUN apt-get update && apt-get -y install \
    software-properties-common gpg wget \
    make libssl-dev

RUN apt-get install -y build-essential libthrust-dev libtbb2-dev libtbb2

# https://apt.llvm.org/
RUN wget https://apt.llvm.org/llvm.sh && \
    chmod +x llvm.sh && \
    ./llvm.sh 15 all
ENV PATH=$PATH:/usr/lib/llvm-15/bin

RUN echo "\
\n#include <execution> \n \
\n#include <algorithm> \n \
\n#include <vector> \n \
int main(void) { \n \
    std::vector<float> images = {1,2,3,4,5}; \n \
    std::vector<float> results; \n \
    results.resize(images.size()); \n \
    std::transform(std::execution::par, images.begin(), images.end(), results.begin(), [](const auto &input){ return input; }); \n \
}" > hello.cpp

RUN clang -std=c++17 -stdlib=libc++ hello.cpp -o hello && ./hello
```

produces following error:

```
hello.cpp:11:26: error: no member named 'execution' in namespace 'std'; did you mean 'exception'?
     std::transform(std::execution::par, images.begin(), images.end(), results.begin(), [](const auto &input){ return input; }); 
                    ~~~~~^~~~~~~~~
                         exception
/usr/lib/llvm-15/bin/../include/c++/v1/exception:100:29: note: 'exception' declared here
class _LIBCPP_EXCEPTION_ABI exception
                            ^
hello.cpp:11:37: error: no member named 'par' in 'std::exception'
     std::transform(std::execution::par, images.begin(), images.end(), results.begin(), [](const auto &input){ return input; }); 
                    ~~~~~~~~~~~~~~~~^
2 errors generated.
The command '/bin/sh -c clang -std=c++17 -stdlib=libc++ hello.cpp -o hello && ./hello' returned a non-zero code: 1
```


Nevertheless, godbold shows that clang-15 should be possible to compile so:
https://godbolt.org/z/3TxoWEMxb
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJzlVkuPpDYQ_jX0xQKBaZruA4d-KiNlZ0ebmU1uIwMFOAs2sk3P7Pz6lIF-ZqY3kfYSpWXcxnaVq776XFQq8-_JbwZaTYwkClol8y4DJ1w6_sbxx_4p7YTpyAs3FclqJkpSKNkQhy6xsdZ4db1vPKnKYYYwkQ-bW2lAGM5q0mpTk5Rl30DkmnChDatryMmeM1Lz1KQpdXPY96L9EW4QubIF0bSEayKkISytwVqZyablOOxPWDt0hS2ISQHMdAqINrk1P1zCK2Sd4VIMry1T3rlTG4nGqAI1nbyd-WPrX3dfPn8iXe87bqHU86fnCr483RN03i3BkK7NmQFEZIbtOOt-P3hKnGg9SBH8aVmYF6bARbhbUIaDdtGrRgpStiV5sbIXAg37BhYmrWuL0kdWHA7Dc9OO17kLWo_4W4wr1WnTo3yO-Dg-1-nQkFTGtNoiQ3fYLoO8Ox3d23pzbz_U1QGbC7-yqpE5rqxeya1t3pmaICLo4rC2vf9KHpaPvzjhxqHTYWSN6LSyEjwd5ZBLOEq5uAYOskriifR4Gg4Ees9FVnc5xjNcn7Foa60S5MZmVpdSIS2bf7J5D5mR6u87uTAYcDSWzveS5w5dECdeXW3qaXRg-kHTuqglM1Yjb1gJGk_ZWNnAoWuKT4jPFJ_IiTdO-C9VKtBdbfT7cuOih__8DdDywQBvfEMfbLt9pFFM6EKqBgVuXGK0f3TPS6HsYerVH2cxw5zmDoZdbXWilRMhaeaZxDtDWGcsD2ZctJ2xWxBvBZhOBBmmrOWI2Xs-9POUWIgqqGvpZW17zbMhabq9V5vsmLLshGVpuMF-nD4pIa4cXg53wl6DfuLdbDX0YwLXpJC48YXjsaCUjeRFRr-SPRkeLoPAJrsZdkdJTL-kgSYFRQRrwN7Y-BQYGiNI_YJuWWaTYGwdpbHFKuc5-S47FGdiEMugHcWccHeiwX-RByfjr35OvL1o0fZ65tg-1NH_TnCNiflGbqM7zzJkzDA4GhmFoz1mgN1JFwbZ922UF0Nwjf0EXkeH5IC0VRjtChQM5-OE1uT517vV-uHhefvHevvwePf5_nm5urs29UOXLDzR9gPehfGPeNdHvmfcyLORHme0-n9w6oftADId8NSkBAEKy5R8rIMeK7DFVGNrLovbgUb4lXWzn56zMGiD2xhHhpEV7hsoW83lPfuCG0lt6O9hj7USKsOqxuJcyjyVdU50JV-wfK2YOVaOdq7DpRSwBNWaX1WOWh7T4WXpMqg0Y-Xyhk_4-Cp_3356TSeQBLNZOJ9O6Ww-yZMwX4QLNjHc1JCclzwnI35a3TrpVJ1cWYpKutRDnWMeOKQD_AD8id9umwi07gCR2kXxfDGfVEk696GYxWGeBuF0USyiaZgW6TwKZmFeREE2qVkKtU4sgSkV8EJ6FX19tJnwhPqU-gtKAz-Kp3Mv8mkaFBlMw0VURCxwpj5g3VIfkZiopDcp7UqNizXXeFmOi5hJeCkAkuG-TPCeVFIlWdlhyYop5_FpXUEjuHmb9GYkvRt_ASv1teU">