Ensure SIZEOF_FORTRAN_T is not empty

Makes sure that SIZEOF_FORTRAN_T is not given an empty
value that can bypass ifdef, and warns the user. Also
Checks in the Makefile for libAtoms that it has been
properly set so that compile failures are less confusing.

Fixes #26

bin/find_sizeof_fortran_t

@@ -33,8 +33,17 @@ program sizeof_fortran_t
 end program sizeof_fortran_t
 EOF
 
-make -I ../../arch -I../.. sizeof_fortran_t > /dev/null
-echo SIZEOF_FORTRAN_T=$(./sizeof_fortran_t)
+# Using && prevents an empty value being added to the makefile
+make -I ../../arch -I../.. sizeof_fortran_t > /dev/null && \
+    echo SIZEOF_FORTRAN_T=$(./sizeof_fortran_t)
+
+# Try to warn that something is wrong
+if [ $? -ne 0 ]; then
+    echo >&2
+    echo Unable to determine SIZEOF_FORTRAN_T >&2
+    echo Check that your compiler is working and try again! >&2
+    echo >&2
+fi
 
 rm sizeof_fortran_t.f90
 rm sizeof_fortran_t

src/libAtoms/Makefile

@@ -44,6 +44,10 @@ endif
 include Makefile.inc
 include Makefile.rules
 
+# indicator that compiler is not set up properly
+ifeq (${SIZEOF_FORTRAN_T},)
+  $(error SIZEOF_FORTRAN_T is not set. Check compiler and re-run 'make config')
+endif
 
 LIBATOMS_F95_FILES = \
   error \