Flang error in Cactus/src/util/PointerTo.F90

[Erik Schnetter]

Flang 12.0.0 (the LLVM Fortran compiler) reports an error in Cactus/src/util/PointerTo.F90. I can make the code compile when I disable the setting #define HAVE_CCTK_F_TYPE_STAR in cctk_Config.h.

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1621195405.31277 Compiling /home/eschnetter/src/CarpetX/Cactus/src/util/PointerTo.F90
current_wd=`pwd` ; cd /home/eschnetter/src/CarpetX/Cactus/configs/sim-llvm/scratch ; /home/eschnetter/src/CarpetX/Cactus/view-compil
ers-llvm/bin/flang -pipe -g -march=native -fcray-pointer -ffixed-line-length-none -O3 -ffp-contract=fast -fno-math-errno -fno-rounding-math -funsafe-math-optimizations  -Wall -Wshadow -Wsurprising -I"/home/eschnetter/src/CarpetX/Cactus/view-llvm/include" -I"/home/
eschnetter/src/CarpetX/Cactus/view-llvm/include" -I"/home/eschnetter/src/CarpetX/spack/opt/spack/linux-ubuntu18.04-skylake_avx512/gc
c-10.3.0/openmpi-4.0.5-r5fts4e7cvxadfzjtlq4pjjuv7e5pcoq/include" -I"/home/eschnetter/src/CarpetX/Cactus/src" -I"/home/eschnetter/src/CarpetX/Cactus/src/include" -I"/home/eschnetter/src/CarpetX/Cactus/configs/sim-llvm/config-data" -I"/home/eschnetter/src/CarpetX/Ca
ctus/configs/sim-llvm/bindings/include" -I"/home/eschnetter/src/CarpetX/Cactus/src/include" -I"/home/eschnetter/src/CarpetX/Cactus/a
rrangements" -I"/home/eschnetter/src/CarpetX/Cactus/configs/sim-llvm/bindings/Configuration/Thorns" -I"/home/eschnetter/src/CarpetX/
Cactus/configs/sim-llvm/bindings/include/Cactus" -I"/home/eschnetter/src/CarpetX/Cactus/src/util" -I"/home/eschnetter/src/CarpetX/Cactus/configs/sim-llvm/bindings/include/Cactus" -c -o $current_wd/PointerTo.F90.o $current_wd/PointerTo.f90
/home/eschnetter/src/CarpetX/Cactus/configs/sim-llvm/build/Cactus/util/PointerTo.f90:409:22: error: Assumed type argument requires a
n explicit interface
    address = transfer(c_loc(var), address)
                       ^^^^^^^^^^

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[Roland Haas]

Can you supply the file configs/sim-llvm/config-data/config.log, please?

The configure test there uses:

      subroutine foo(a)
        use iso_c_binding, only: c_loc,c_intptr_t
        implicit none
        type(*),dimension(..),target :: a
        integer(kind=kind(c_intptr_t)) :: b
        b = transfer(c_loc(a), b)
      end subroutine

      program main

      end

which is (almost other than the c_intptr_t) the same code as inf PointerTo.F90:

CCTK_POINTER function CCTK_PointerTo(var)
  use iso_c_binding, only: c_loc
  implicit none

  type(*), dimension(..), TARGET :: var
  CCTK_POINTER :: address

  address = transfer(c_loc(var), address)
  CCTK_PointerTo = address
end function

so I would have expected some configure test failing and the define not to be set.

[Roland Haas]

Downgrade to minor since the flang compiler is not used in any ET release.

[Erik Schnetter]

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[Erik Schnetter]

These are the relevant lines in config.log:

configure:2105: checking whether the Fortran compiler (/home/eschnetter/src/CarpetX/Cactus/view-compilers-llvm/bin/flang  ) supports TYPE(*) for CCTK_PointerTo
configure:2130: /home/eschnetter/src/CarpetX/Cactus/view-compilers-llvm/bin/flang -c -pipe -g -march=native -fcray-pointer -ffixed-line-length-none conftest.f 1>&5
conftest.f:7:22: error: Assumed type argument requires an explicit interface
          b = transfer(c_loc(a), b)
                       ^^^^^^^^
/home/eschnetter/src/CarpetX/Cactus/view-compilers-llvm/bin/f18: Semantic errors in conftest.f
flang: in /home/eschnetter/src/CarpetX/Cactus/configs/sim-llvm-debug/config-data, f18 failed with exit status 0: /home/eschnetter/src/CarpetX/Cactus/view-compilers-llvm/bin/f18 -module-suffix .f18.mod -intrinsic-module-directory /home/eschnetter/src/CarpetX/Cactus/view-compilers-llvm/include/flang -c -pipe -g -march=native -fcray-pointer -ffixed-line-length-none conftest.f

That is, the error is reported, but somehow doesn’t make it back to the configure script.

[Roland Haas]

ok, bumping this to major again since the error really should be reported.

[Roland Haas]

uh f18 failed with exit status 0 is not very great behaviour by flang. Looks like a bug in the f18 compiler to me, in that it does not set a non-zero exit code when finding this particular error.

[Roland Haas]

Looking into this might be a hard hackathon task (since it involves autoconf in some capacity).