(Closes #1770) make eg20 compile

changelog

@@ -1,3 +1,5 @@
+   55) PR #3603 for #1770. Make lfric/eg20 compile.
+
    54) PR #3587 towards #2216. Adds a new KernelInlineTrans to do
    a deferred InlineTrans on Kernels after lower the PSy layer.
 

doc/tutorials_and_examples/lfric_examples.rst

@@ -341,4 +341,4 @@ algorithm layer run:
 .. code-block:: bash
 
     cd eg20/
-    psyclone-kern -gen alg ../code/testkern_mod.F90
+    psyclone-kern -api lfric -gen alg ../code/testkern_mod.F90

examples/lfric/eg20/Makefile

@@ -7,13 +7,18 @@
 
 include ../lfric_common.mk
 
-GENERATED_FILES = test_alg_mod_psy.f90 testkern_mod.F90 test_alg_mod.[fx]90
+GENERATED_FILES = test_alg_mod_psy.f90 testkern_mod.F90 test_alg_mod.[fx]90 \
+    *.o *.mod *.exe
+
+OBJECTS = testkern_mod.o test_alg_mod_psy.o test_alg_mod.o driver.o
 
 run: compile
+	@echo "The compiled code for lfric/eg20 is not executable."
 
-compile: transform ${LFRIC_LIB}
-	@echo "#1770 Compilation is not supported: the generated code must be "
-	@echo "inserted into an LFRic mini-app."
+# Although we compile and link, the resulting binary will not execute (because the
+# driver does not do the necessary setup).
+compile: transform ${LFRIC_LIB} ${OBJECTS}
+	$(F90) $(F90FLAGS) -o will_not_run.exe ${OBJECTS} ${LDFLAGS}
 
 # Dependencies
 %.F90:
@@ -36,3 +41,9 @@ test_alg_mod_psy.f90 test_alg_mod.f90: test_alg_mod.x90
 
 allclean: clean
 	make -C $(LFRIC_PATH) allclean
+
+%.o: %.F90
+	$(F90) $(F90FLAGS) -c $<
+
+%.o: %.f90
+	$(F90) $(F90FLAGS) -c $<

examples/lfric/eg20/driver.f90

@@ -0,0 +1,18 @@
+! -----------------------------------------------------------------------------
+! SPDX-FileCopyrightText: Copyright (c) 2020-2026 Science and Technology
+!                         Facilities Council
+! SPDX-License-Identifier: BSD-3-Clause
+! See the full LICENSE file in the project root for details.
+! -----------------------------------------------------------------------------
+!> A bare-bones driver program that allows the generated code to be compiled
+!! and linked. The result will not execute because no attempt has been made
+!! to perform the setup that a real LFRic application requires.
+program driver
+  USE mesh_mod, ONLY: mesh_type
+  use test_alg_mod, only: test_alg
+  implicit none
+  TYPE(mesh_type), POINTER :: mesh
+
+  call test_alg(mesh)
+
+end program driver