[Openmp-dev] Bug in clang/openmp: max-reduction fails if data type is "long double"

[Stefan Illy via Openmp-dev]

Hello everybody,

When I compile the simple test program attached below I get the 
following error message:

openmpbug.cc:(.text+0x2de): undefined reference to 
`__sync_val_compare_and_swap_16'
openmpbug.cc:(.text+0x3a7): undefined reference to 
`__sync_val_compare_and_swap_16'
clang-3.8: error: linker command failed with exit code 1 (use -v to see 
invocation)

This is caused by the OMP max-reduction statement. It also fails if I 
switch from "max" to "min".
I use version 3.8 of clang on an Ubuntu 14.04 LTS system. It also fails 
with version 3.9 (trunk, self-compiled).
If I switch the floating point data type (real_t) from "long double" to 
"double" or "float", the code compiles and runs without problems.

I hope this helps to make clang+openmp even better!


Here comes the simple test program:
---------------------------------------SNIP-------------------------------------------
#include <iostream>

using namespace std;

//typedef float real_t;
//typedef double real_t;
typedef long double real_t;

int
main()
{
   real_t maxval = -1.0e-10;
#pragma omp parallel for reduction(max: maxval)
   for (int i = 1; i <= 1000; i++) maxval = max(maxval, real_t(i));
   cout << maxval << endl;
   return 0;
}
------------------------------------SNIP------------------------------------------------

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