(Re)allocation of allocatable arrays on assignment - F2003

[Tobias Burnus]

On 11/04/2010 03:19 PM, Dominique Dhumieres wrote:
> First the good news:
> (1) the last patch woke up one bug of my collection (pr28849)
> with another bound problem:
>
> [macbook] f90/bug% cat pr28849_db.f90
[...]
>    print *, "...and with wrong shape (should fail with bounds checking on)"
>    a(:,:) = reshape (v(:), (/ 2, 1 /) )
>    b(:,:) = reshape (v(:), (/ 1, 2 /) )

Without bound checks (and realloc-lhs) I get the same result as with 
ifort and crayftn. However, for the last line shown above (line 20) I 
get with gfortran a segfault which valgrind diagnoses as:

==25067== Invalid write of size 4
==25067==    at 0x40188D: MAIN__ (pr28849_db.f90:20)


> So either a is relocated as a(2,1) (b as b(1,2)) and the bounds
> are inconsistent, or it is not and there should be a run time
> error as when compiled with -std=f95.

I think the program is valid Fortran 2003 and thus no bound check error 
should be printed. Despite ifort and crayftn showing the same bounds, I 
think you are right that the bounds are wrong.

Some other results:

a) I immediately get a segfault if I comments out the allocate statement.

b) If I comment out the first part of the example ("correct bounds", 
i.e. not reallocation), I get the result:

  ...and with wrong shape (should fail with bounds checking on)
  a(:,1) =   1.0000000
            1           1           1           2
  b(:,1) =   1.0000000     -1.33410292E-32
            1           1           2           1

Note the uninitialized value for b(2,1).


Tobias