Make guarding of 0 sized arrays in FIELD_ACCESS_MODULE optional

.github/workflows/build.yml

@@ -256,5 +256,5 @@ jobs:
         dependency_branch: develop
         dependency_cmake_options: |
           ecmwf-ifs/fiat: "-DCMAKE_BUILD_TYPE=${{ matrix.build_type }} -G Ninja -DENABLE_TESTS=OFF ${{ matrix.cmake_options}}"
-        cmake_options: "-DCMAKE_BUILD_TYPE=${{ matrix.build_type }} ${{ matrix.cmake_options }} -G Ninja -DENABLE_ACC=OFF -DENABLE_MPI=ON -DENABLE_IO_PARALLEL=ON -DENABLE_GET_VIEW_ABORT=${{ matrix.get_view_abort }} -DENABLE_DELAYED=${{ matrix.delayed }} ${{matrix.cmake_options}}"
+        cmake_options: "-DCMAKE_BUILD_TYPE=${{ matrix.build_type }} ${{ matrix.cmake_options }} -G Ninja -DENABLE_ACC=OFF -DENABLE_MPI=ON -DENABLE_IO_PARALLEL=ON -DENABLE_GET_VIEW_ABORT=${{ matrix.get_view_abort }} -DENABLE_DELAYED=${{ matrix.delayed }} -DENABLE_GUARD_0_SIZE=${{ matrix.delayed }} ${{matrix.cmake_options}}"
         ctest_options: "${{ matrix.ctest_options }}"

CMakeLists.txt

@@ -96,6 +96,11 @@ ecbuild_add_option( FEATURE DELAYED
 	DEFAULT OFF
 )
 
+##Guard 0 sized allocations
+ecbuild_add_option( FEATURE GUARD_0_SIZE
+                    DESCRIPTION "Enable this option to guard 0 sized arrays in FIELD_ACCESS module"
+                    DEFAULT ON
+)
 
 ## fypp preprocessor flags
 if(HAVE_CUDA OR HAVE_HIPFORT)
@@ -104,6 +109,9 @@ endif()
 if(fiat_FOUND)
   list( APPEND fypp_defines "-DWITH_FIAT")
 endif()
+if(HAVE_GUARD_0_SIZE)
+  list( APPEND fypp_defines "-DWITH_GUARD_0_SIZE")
+endif()
 
 ## build precision independent srcs
 add_subdirectory(src)

Readme.md

@@ -51,6 +51,7 @@ Features of FIELD_API can be toggled by passing the following argument to the CM
 | HIPFORT | OFF | Enable the use of advanced functionality via the hipfort runtime API e.g. host memory pinning, fast strided copies, asynchronous data transfers, etc.|
 | GET_VIEW_ABORT | ON | If activated, get_view will abort when the data are not present on CPU. |
 | DELAYED | OFF | If activated, field owners will be delayed by default. |
+| GUARD_0_SIZE | ON | If activated, the module-level `GET_HOST_DATA_*`/`GET_DEVICE_DATA_*` accessors in `FIELD_ACCESS_MODULE` return a size-1 dummy pointer for 0-sized fields instead of the underlying 0-sized array. |
 | IO_SERIAL | OFF | Use serial HDF5 to read and write FieldAPI variables.  |
 | IO_PARALLEL | OFF | Use  HDF5 (rank defined by MPI) to read and write FieldAPI variables.  |
 

src/util/field_RANKSUFF_access_module.fypp

@@ -84,7 +84,11 @@ CONTAINS
 #:for rank in range(ft.rank)
          ISIZE = ISIZE * (IUBOUNDS(${rank + 1}$) - ILBOUNDS(${rank + 1}$) + 1)
 #:endfor
+#:if defined('WITH_GUARD_0_SIZE')
          IF (ISIZE > 0) LEXISTS = .TRUE.
+#:else
+         LEXISTS = .TRUE.
+#:endif
       ENDIF
       IF (LEXISTS) THEN
         CALL FIELD_PTR%GET_${what}$_DATA_${mode}$ (PTR)

tests/CMakeLists.txt

@@ -265,8 +265,9 @@ foreach(TEST_FILE ${TEST_FILES})
     target_compile_definitions( ${TEST_NAME}.x PRIVATE
                                 $<$<BOOL:${HAVE_IO}>:HDF5::HDF5>
                                 $<${HAVE_OMP_OFFLOAD}:OMPGPU>
-                                $<${HAVE_CUDA}:_CUDA> 
-                                $<${HAVE_HIPFORT}:_HIP> )
+                                $<${HAVE_CUDA}:_CUDA>
+                                $<${HAVE_HIPFORT}:_HIP>
+                                $<${HAVE_GUARD_0_SIZE}:WITH_GUARD_0_SIZE> )
 
     if( DEFAULT_PRECISION MATCHES sp )
        target_compile_definitions( ${TEST_NAME}.x PRIVATE PARKIND1_SINGLE )

tests/test_0_sized_transfer.F90

@@ -27,9 +27,15 @@ PROGRAM TEST_0_SIZED_TRANSFER
         ENDIF
 
         PTR => GET_HOST_DATA_RDONLY(O)
+#ifdef WITH_GUARD_0_SIZE
         IF( SIZE(PTR) /= 1 )THEN
           CALL FIELD_ABORT("ALLOCATION SHOULD BE OF SIZE==1")
         ENDIF
+#else
+        IF( SIZE(PTR) /= 0 )THEN
+          CALL FIELD_ABORT("ALLOCATION SHOULD BE OF SIZE==0")
+        ENDIF
+#endif
 
         !...Ensure data can be copied to device and back safely
         CALL O%SYNC_DEVICE_RDWR()

tests/test_0_sized_transfer_wrap.F90

@@ -30,9 +30,15 @@ PROGRAM TEST_0_SIZED_TRANSFER
   ENDIF
 
   PTR => GET_HOST_DATA_RDONLY(W)
+#ifdef WITH_GUARD_0_SIZE
   IF( SIZE(PTR) /= 1 )THEN
     CALL FIELD_ABORT("ALLOCATION SHOULD BE OF SIZE==1")
   ENDIF
+#else
+  IF( SIZE(PTR) /= 0 )THEN
+    CALL FIELD_ABORT("ALLOCATION SHOULD BE OF SIZE==0")
+  ENDIF
+#endif
 
   !...Ensure data can be copied to device and back safely
   CALL W%SYNC_DEVICE_RDWR()