in-place conversion macro writes into INPUT argument #6572
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In fint_2_int.h there are some conversion macros for logicals. It has
one path for OMPI_SIZEOF_FORTRAN_LOGICAL != SIZEOF_INT where a new array
would be allocated and the conversions then might expand to
c_array[i] = (array[i] == 0 ? 0 : 1)
and another path for OMPI_SIZEOF_FORTRAN_LOGICAL == SIZEOF_INT where it
does things "in place", so the same conversion there would just be
array[i] = (array[i] == 0 ? 0 : 1)
The problem is some of the logical arrays being converted are INPUT
arguments. And it's possible for some compilers to even put the argument
in read-only memory so the above "in place" conversion SEGV's. A
testcase I have used
call MPI_CART_SUB(oldcomm, (/.true.,.false./), newcomm, ierr)
and gfortran put the second arg in read-only mem.
In cart_sub_f.c you can trace the ompi_fortran_logical_t *remain_dims arg.
remain_dims[] is for input only, but the file uses
OMPI_LOGICAL_ARRAY_NAME_DECL(remain_dims);
OMPI_ARRAY_LOGICAL_2_INT(remain_dims, ndims);
PMPI_Cart_sub(..., OMPI_LOGICAL_ARRAY_NAME_CONVERT(remain_dims), ...);
OMPI_ARRAY_INT_2_LOGICAL(remain_dims, ndims);
to convert it to c-ints make a C call then restore it to Fortran logicals
before returning.
It's not always wrong to convert purely in-place, eg cart_get_f.c has
a periods[] that's exclusively for OUTPUT and it would be fine with the
macros as they were. But I still say the macros are invalid because they
don't distinguish whether they're being used on INPUT or OUTPUT args and
thus they can't be used in a way that's legal for both cases.
It might be possible to fix the macros by adding more of them so that
cart_create_f.c and cart_get_f.c would use different macros that give
more context. But my fix here is just to turn off the first block and
make all paths run as if OMPI_SIZEOF_FORTRAN_LOGICAL != SIZEOF_INT.
The main macros that get enlarged by this change are
define OMPI_ARRAY_LOGICAL_2_INT_ALLOC : mallocs now
define OMPI_ARRAY_LOGICAL_2_INT : also mallocs now
But these are only used in 4 places, three of which are the purpose of
this checkin, to avoid the former in-place expansion of an INPUT arg:
cart_create_f.c
cart_map_f.c
cart_sub_f.c
and one of which is an OUPUT arg that was fine and that gets
unnecessarily expanded into a separate array by this checkin.
cart_get_f.c
So I think an unnecessary malloc in cart_get_f.c is the only downside
to this change, where the logicals array argument could have been used
and converted in place.
Signed-off-by: Mark Allen <markalle@us.ibm.com>
Update provided by Gilles Gouaillardet to keep the in-place option
if OMPI_FORTRAN_VALUE_TRUE == 1 where no conversion is needed.
Signed-off-by: Gilles Gouaillardet <gilles@rist.or.jp>
(cherry picked from commit 0a7f1e3)
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Mellanox CI failed due to out of space. |
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retest |
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bot:retest |
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@markalle we generally |
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I did cherry-pick x, so the commit itself has the full text with at the bottom. Maybe the part that made it look weird is that when I created the github pull request I replaced the text of the commit that would have normally been the top item in the pull request. |
ggouaillardet
approved these changes
Apr 10, 2019
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@markalle my bad, the commit is fine. As you guessed, I was mislead by the text of the PR you manually edited.
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Cray keeps failing for some reason. Try again. bot:ompi:retest |
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merge of 0a7f1e3
#6448
into v4.0.x