Preprocessing macro __GNUC__ undefined for mpic++

Accelerated Computing HPC Compilers Legacy PGI Compilers
1

Hello, it seems that the preprocessing macro GNUC is undefined for mpic++ but defined for pgc++.
I’m not sure whether the issue is with pgc++ or the mpi wrapper, but the issue does not occur for Intel so I’m posting here first.

The following example code demonstrates the problem.

#ifdef __GNUC__
#warning "__GNUC__ is defined"
#else
#warning "__GNUC__ is not defined"
#endif

With recent versions of OpenMPI and pgc++, the compile-time output is:

mach5% mpic++ --version

pgCC 15.10-0 64-bit target on x86-64 Linux -tp sandybridge
The Portland Group - PGI Compilers and Tools
Copyright (c) 2015, NVIDIA CORPORATION.  All rights reserved.
mach5% mpirun --version
mpirun (Open MPI) 1.10.1

Report bugs to http://www.open-mpi.org/community/help/
mach5% mpic++ -c test.cpp
"test.cpp", line 4: warning: #warning directive: "__GNUC__ is not defined"
  #warning "__GNUC__ is not defined"
   ^

mach5% pgc++ -c test.cpp
"test.cpp", line 2: warning: #warning directive: "__GNUC__ is defined"
  #warning "__GNUC__ is defined"
   ^

I’ve tried PGI 15.10 with OpenMPI 1.10.1 (shown here) and PGI 12.9 with OpenMPI 1.6.2. Intel 16.0 with OpenMPI 1.10.1 does not have this problem.

2

Well, I found (after some digging) the source of the above problem. mpic++ points to pgCC (or pgcpp), which is not the same as pgc++. A PGI post helped me understand what is going on: Account Login | PGI

Passing the --gnu flag to mpic++ solves almost all of my problems, except the following issue.

Consider the following code:

#include <mpi.h>
int main()
{
  int id;
  MPI_Comm_rank(MPI_COMM_WORLD, &id);
  return 0;
}

The code compiles fine with mpic++, but fails when compiling with mpic++ --gnu.

mach5% mpic++ simple_mpi.cpp
mach5% mpic++ --gnu simple_mpi.cpp
/tmp/pgCCOryb4A-0xatp.o: In function `MPI::Intracomm::Intracomm()':
/stage/mpi/OpenMPI/1.10.1/PGI/15.10/include/openmpi/ompi/mpi/cxx/intracomm.h:25: undefined reference to `MPI::Comm::Comm()'
/tmp/pgCCOryb4A-0xatp.o: In function `MPI::Intracomm::Intracomm(ompi_communicator_t*)':
/stage/mpi/OpenMPI/1.10.1/PGI/15.10/include/openmpi/ompi/mpi/cxx/intracomm_inln.h:23: undefined reference to `MPI::Comm::Comm()'
/tmp/pgCCOryb4A-0xatp.o:(.data._ZTVN3MPI8DatatypeE[_ZTVN3MPI8DatatypeE]+0x78): undefined reference to `MPI::Datatype::Free()'
/tmp/pgCCOryb4A-0xatp.o:(.data._ZTVN3MPI3WinE[_ZTVN3MPI3WinE]+0x48): undefined reference to `MPI::Win::Free()'

I feel like I’m missing a library or something, but I’ve been unable to find it.
I have tried passing my specific gcc version (4.8.3) and other versions. As before, this is with PGI 15.10 and OpenMPI 1.10.1.

3

Hi Ross,

Sorry, but you’ll need to rebuild OpenMPI to using pgc++ (aka pgcpp --gnu) or g++. Different C++ compilers use different name mangling so the OpenMPI symbol names in object files will be different depending upon if you built using g++ naming or our older pgcpp name mangling.

  • Mat