Add regression test for #243

 Confirmed that #243 is fixed as of:
 GNU Fortran (Homebrew GCC HEAD-244466_1 --without-multilib) 7.0.0
 20170114 (experimental)

 Only run regression test if on GFortran >= 7.0.0 since it's not
 backported to 5 and 6 branches

Author: zbeekman

CMakeLists.txt

@@ -429,6 +429,10 @@ if(opencoarrays_aware_compiler)
   endif()
 
   # Regression tests based on reported issues
+  if(gfortran_compiler AND (CMAKE_Fortran_COMPILER_VERSION VERSION_GREATER_EQUAL 7.0.0))
+    # GFortran PR 78505 only fixed on trunk/gcc 7
+    add_mpi_test(source-alloc-no-sync 8 ${tests_root}/regression/reported/source-alloc-sync)
+  endif()
   add_mpi_test(convert-before-put 3 ${tests_root}/regression/reported/convert-before-put)
   add_mpi_test(event-post 3 ${tests_root}/regression/reported/event-post)
 else()

src/tests/regression/reported/CMakeLists.txt

@@ -3,3 +3,7 @@ target_link_libraries(convert-before-put OpenCoarrays)
 
 add_executable(event-post issue-293-silent-event-failure.F90)
 target_link_libraries(event-post OpenCoarrays)
+
+add_executable(source-alloc-sync issue-243-source-allocation-no-sync.f90)
+target_link_libraries(source-alloc-sync OpenCoarrays)
+

src/tests/regression/reported/issue-243-source-allocation-no-sync.f90

@@ -0,0 +1,50 @@
+program source_allocation_no_sync
+  !! author: Damian Rouson and Izaak Beekman
+  !! category: regression
+  !!
+  !! [Issue #243](https://github.com/sourceryinstitute/opencoarrays/issues/243)
+  !!
+  !! [GFortran PR 78505](https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78505):
+  !!
+  !! @note The test must be run with less than or equal to 32 images,
+  !! and the number of images must be a power of two. Valid numbers of
+  !! images are: 2, 4, 8, 16, or 32
+  !!
+  !! Sourced allocation of a coarray object performs a synchronization
+  !! after the allocation, BUT *before* the assignment of
+  !! `source`. This violates the
+  !! [standard](http://open-std.org/JTC1/SC22/WG5/5559) Section
+  !! 9.7.1.2, paragraph 4:
+  !!
+  !! > When an ALLOCATE statement is executed for which an
+  !! > allocate-object is a coarray, there is an implicit
+  !! > synchronization of all active images in the current team. On
+  !! > those images, if no error condition other than
+  !! > STAT_STOPPED_IMAGE or STAT_FAILED_IMAGE occurs, execution of
+  !! > the segment (11.6.2) following the statement is delayed until
+  !! > all other active images in the current team have executed the
+  !! > same statement the same number of times in this team. The
+  !! > coarray shall not become allocated on an image unless it is
+  !! > successfully allocated on all active images in this team.
+  !!
+
+  implicit none
+  integer, allocatable :: f(:)[:]
+  integer, parameter :: num_points=32
+  integer :: me,ni,my_num_points,neighbor_last_element
+  me = this_image()
+  if (mod(num_points,num_images())/=0) error stop "num_points not evenly divisible by num_images()"
+  my_num_points = num_points/num_images()
+  allocate( f(my_num_points)[*], source = 1 )
+  if (me>1) then
+     neighbor_last_element = f(my_num_points)[me-1]
+     if (neighbor_last_element /=1) then
+        print *,"Image ",me," gets ",neighbor_last_element
+        error stop "Synchronization did not happen after assignment in sourced allocation!"
+     end if 
+  end if
+  sync all
+  if ( me == 1 ) then
+     write(*,'(a)') "Test passed."
+  end if
+end program source_allocation_no_sync