<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/139636>139636</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Flang OpenMP issue with copy private clauses on common blocks.
        </td>
    </tr>

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

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

    <tr>
      <th>Reporter</th>
      <td>
          scamp-nvidia
      </td>
    </tr>
</table>

<pre>
    We believe the following section of code should work properly as it works with NVIDIA's nvfortran 25.3 and GNU's gfortran version 15.1. 

```
Program main
  implicit none
  call test_common()
End Program main

subroutine test_common()
  implicit none
  common /vals/ val
  integer, target :: targ
  integer, pointer :: ptr
  integer :: val
  !$omp threadprivate (/vals/)

  targ = 200
  !$omp parallel private(ptr) shared(targ) default(none)
  !$omp single
  val = 300
  ptr => targ ! set private pointer to shared storage
#ifdef NO_COMMON
  !$omp end single copyprivate(val, ptr)
#else
  !$omp end single copyprivate(/vals/, ptr)
#endif
  if (.not. associated(ptr)) then
     print *, "ERROR: ptr is not associated"
  else
     if (ptr == 200 .and. val == 300) then
 print *, "SUCCESS"
     else
        print *, "FAILURE"
     end if
  end if
  !$omp end parallel
end subroutine test_common
```
By default, the code tries to do a copyprviate on a common block at the end of an OpenMP region, but all but 1 thread get the wrong behavior.

```
scamp@milan2:/local/home/scamp/common_issue$ export OMP_NUM_THREADS=4
scamp@milan2:/local/home/scamp/common_issue$ flang test.F90 -fopenmp -o test
flang-21: warning: OpenMP support in flang is still experimental [-Wexperimental-option]
scamp@milan2:/local/home/scamp/common_issue$ ./test
 SUCCESS
 ERROR: ptr is not associated
 ERROR: ptr is not associated
 ERROR: ptr is not associated
scamp@milan2:/local/home/scamp/common_issue$ gfortran test.F90 -fopenmp -o test
scamp@milan2:/local/home/scamp/common_issue$ ./test
 SUCCESS
 SUCCESS
 SUCCESS
 SUCCESS
scamp@milan2:/local/home/scamp/common_issue$ nvfortran test.F90 -mp -o test
scamp@milan2:/local/home/scamp/common_issue$ ./test
 SUCCESS
 SUCCESS
 SUCCESS
 SUCCESS
```
This is all with almost the latest version of Flang:

```
scamp@milan2:/local/home/scamp/common_issue$ flang --version
flang version 21.0.0git (https://github.com/llvm/llvm-project 227328f6f6d32e93a6c3c0d3c82a7601f92f9abb)
```
As seen in the code, you can work around it by not using the common block, but it should work with the common block as well. 
</pre>
<img width="1" height="1" alt="" src="http://email.email.llvm.org/o/eJzEVk1v4zYQ_TX0ZWCBovylgw_aOG4XaJJFsukeA0oayexSpEBSSv3vC1KS7bhBt0UWKGDAEjWcN_M4bzjcWlErxC1ZfiLL3Yx37qDN1ha8aeeqF6Xgs1yXx-03hBylwB7BHRAqLaV-FaoGi4UTWoGuoNAlgj3oTpbwqs13aI1u0cgjcAvChTULr8Id4P73z7vPGWFrC6qvtHGGK2DLKAGuSvjl_jl8qqcvPRrrQeJlFEdAaOZ_Kzr-aPbF6NrwBhouFKEZgGhaKQrhQGmFYaXgUoJD614K3TRaEbYhLCU0u1UlXO0nNLNdbnTnhMJ3N72LEEyAsH3PpSVsDz2Xg61yWKMh7AYcNzU6IElGkiy8XVu02r-YyaR15tJiWp5cExYTttBNC-5gkJetET13CCHSKZAh5mDvEYEkO2CUXjloueFSooTRB2EbD85SsAdusCRsE-JlKZRY8U46wjYh-5GSsysrVC0HVnouA14y4rXO57Ajye0YC4vBoptAT-k7PcKCddrw2nsjLBFViRXcP7zcPNzdPdxf4aIqR2wodHs8J-Lp8tyGfAZPKC3-2-2XVF55UaWohgOqPOmR0i4Cbq0uBHeBtNGcpV45Q3kC-HyVA8Iy75Ewdvv4-PA4HjgIC0q7N25Y2HgKGibAE5_hSCHiqowm0ifeL6CvYZ-eb25un54m__AW4p0499nn354fby83qBJGDi4e37I61RahWSD5fXW9FfWn47nObkLXCQ3GGYHWl0epgY_n1HuSQKuwEFSYS118B-7CPg-pK-AKHlpUd1_AYC28mm8g7xz4zuD_41FD4BXq970arWrI8cB7oU30974T-iRZ0EZIrpiXJttLXfhi2x90g4TtBxO2H-J6EdZ2SNgC8M9WGwcPd19e7p_vXr7--nib7Z5Islt8zG8luaoDq9E-pTCvdIuqaWGuwyKhWbCYs9gX2ys3SqjaP47U2K4NgQk1uhIWrBNS-ojRiAaV89W1_DT_drky162_B8hy97H4I8L2Y6AwFSfN4Afy-DkWHwj7dFX9E_M_n5YfPX4A8Xwvn1P6n7O5lN7Xg7D-EL14w0jBZaPtoFvJvfPT1KAr2PtS9iH-TAkP-pjPR5xJWidcFkc0orXw7XNzcK61g3vC9rVwhy6PCt14ONlPf_PW6D-wcMDYOmGbalWtyoRhmvBVkRS0TIoN4-sVjauUVSnP8_Eiukgos2ARlRfw1DN9ozvqDgquhsGMG935Vu0gPwYZdP7aG-3P_XNqkMK9GesC3de2fsZ7RSkjmJXbpEyTlM9wG68Xa5rSNGWzw3bN4uUqXy-TPMc121SLFcV0xXlerdNyk1czsWWULekyZiyhScwizMuCrhdlmeMKE8zJgmLDhYw8V5E29SwcxjZO0lWymkmeo7RhlmUsnIW_ppa7mdkGcvOutmRBpbDOnl044SRuQ4VMTTB4HfL0F8xpOCkk7yxaf9Nc5m6jWWfk9r8dMWH7AOOnijH-fsv-CgAA__-8qadV">