<html>
    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Compilation errors when including iostream in OpenMP NVPTX offloading code"
   href="https://bugs.llvm.org/show_bug.cgi?id=41861">41861</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Compilation errors when including iostream in OpenMP NVPTX offloading code
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>OpenMP
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Other
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Linux
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>enhancement
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>Clang Compiler Support
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>p.atkinson@bristol.ac.uk
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>The following code will fail to compile with Clang configured to use OpenMP
NVPTX offloading. 

#include <cstdio>
#include <iostream>

int main()
{
  #pragma omp target
  {
    printf("foo\n");
  }
}

Compiler output:

~ $ clang++ test.cpp -fopenmp -fopenmp-targets=nvptx64-nvidia-cuda
-Xopenmp-target -march=sm_60
In file included from test.cpp:2:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/iostream:39:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/ostream:38:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/ios:42:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/ios_base.h:39:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/ext/atomicity.h:35:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/x86_64-redhat-linux/bits/gthr.h:148:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/x86_64-redhat-linux/bits/gthr-default.h:35:
In file included from /usr/include/pthread.h:24:
/usr/include/time.h:189:16: error: functions that differ only in their return
type cannot be overloaded
extern clock_t clock (void) __THROW;
       ~~~~~~~ ^
/lustre/home/br-patkinson/modules/x86_64/llvm/install/lib/clang/9.0.0/include/__clang_cuda_device_functions.h:1496:16:
note: previous definition is here
__DEVICE__ int clock() { return __nvvm_read_ptx_sreg_clock(); }
           ~~~ ^
In file included from test.cpp:2:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/iostream:39:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/ostream:38:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/ios:42:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/ios_base.h:41:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/locale_classes.h:40:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/string:52:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/bits/basic_string.h:2815:
In file included from
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/ext/string_conversions.h:41:
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/cstdlib:166:3:
error: declaration conflicts with target of using declaration already in scope
  abs(long __i) { return __builtin_labs(__i); }
  ^
/lustre/home/br-patkinson/modules/x86_64/llvm/install/lib/clang/9.0.0/include/__clang_cuda_cmath.h:40:17:
note: target of using declaration
__DEVICE__ long abs(long __n) { return ::labs(__n); }
                ^
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/cstdlib:122:11:
note: using declaration
  using ::abs;
          ^
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/cstdlib:174:3:
error: declaration conflicts with target of using declaration already in scope
  abs(long long __x) { return __builtin_llabs (__x); }
  ^
/lustre/home/br-patkinson/modules/x86_64/llvm/install/lib/clang/9.0.0/include/__clang_cuda_cmath.h:39:22:
note: target of using declaration
__DEVICE__ long long abs(long long __n) { return ::llabs(__n); }
                     ^
/usr/lib/gcc/x86_64-redhat-linux/4.8.5/../../../../include/c++/4.8.5/cstdlib:122:11:
note: using declaration
  using ::abs;
          ^
3 errors generated.


It seems there's a declaration conflict between the C standard library headers
and the '__clang_cuda' headers.

When '#include <iostream>' is removed from the above example, the code compiles
and works fine.</pre>
        </div>
      </p>


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