[ET Trac] [Einstein Toolkit] #581: Pass unallocated arrays to Fortran as NULL pointers

[Einstein Toolkit]

#581: Pass unallocated arrays to Fortran as NULL pointers
--------------------------+-------------------------------------------------
  Reporter:  eschnett     |       Owner:        
      Type:  enhancement  |      Status:  review
  Priority:  major        |   Milestone:        
 Component:  Cactus       |     Version:        
Resolution:               |    Keywords:        
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Comment (by rhaas):

 while I think I can definitely construct a situation where a compiler is
 perfectly correct in trying to access the NULL pointer, namely something
 like:

 {{{
 CCTK_REAL gxx(cctk_lsh(1), cctk_lsh(2), cctk_lsh(3))
 CCTK_REAL betax(cctk_lsh(1), cctk_lsh(2), cctk_lsh(3))
 ...
 gxxL = gxx(i,j,k)
 if(shift_state.ne.0) then
   bx = betax(i,j,k)
 else
   bx = 0.0
 endif
 }}}

 I think that unless we actually know of a compiler that gives segfaults in
 this case I would think that the benefit of having unallocated grid
 functions detected in Fortran outweights the undocumented behaviour we
 exploit here (plus we are already using undocumented/compiler-specific
 features when calling Fortran code from C).

 I compiles for me and seems to not crash the testsuites (gcc 4.6). Please
 apply.

-- 
Ticket URL: <https://trac.einsteintoolkit.org/ticket/581#comment:2>
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