[petsc-dev] Strange "Warnings" When Compiling With -flto

[Matthew Knepley]

On Wed, Jun 9, 2021 at 5:07 PM Jacob Faibussowitsch <jacob.fai at gmail.com>
wrote:

> Hello All,
>
> I’m getting these strange “warnings” (if you can even call them that),
> about struct vector alignments all over the shop when compiling with link
> time optimization enabled on summit. For reference this is with
> spectrum-mpi wrapping gcc v10.2.0. Here are a few examples:
>
> /autofs/nccs-svm1_home1/jfaibussow/petsc/src/mat/impls/baij/seq/baij.c: In
> function 'MatDuplicateNoCreate_SeqBAIJ':
> /autofs/nccs-svm1_home1/jfaibussow/petsc/src/mat/impls/baij/seq/baij.c:3250:21:
> note: the layout of aggregates containing vectors with 8-byte alignment has
> changed in GCC 5
>  3250 |   c->bs2         = a->bs2;
>       |                     ^
>
> autofs/nccs-svm1_home1/jfaibussow/petsc/src/dm/dt/dualspace/impls/lagrange/dspacelagrange.c:
> In function 'PetscDualSpaceSetUp_Lagrange':
> /autofs/nccs-svm1_home1/jfaibussow/petsc/src/dm/dt/dualspace/impls/lagrange/dspacelagrange.c:2291:15:
> note: the layout of aggregates containing vectors with 8-byte alignment has
> changed in GCC 5
>  2291 |     sp->spdim = sp->spintdim = spdim;
>       |               ^
>
> /autofs/nccs-svm1_home1/jfaibussow/petsc/src/mat/impls/sell/mpi/mpisell.c:
> In function 'MatDuplicate_MPISELL':
> /autofs/nccs-svm1_home1/jfaibussow/petsc/src/mat/impls/sell/mpi/mpisell.c:1232:27:
> note: the layout of aggregates containing vectors with 8-byte alignment has
> changed in GCC 5
>  1232 |   a->size         = oldmat->size;
>       |                           ^
>
> There doesn’t seem to be anything the compiler wants you to do, which is
> strange. It just tells you about it. Googling it has not yielded useful
> info either. Is this our own buggy code at fault or just an internal
> compiler logging so rare that they forgot to turn it off?
>

There seems to be a discussion of the option to turn these off here:


https://stackoverflow.com/questions/52020305/what-exactly-does-gccs-wpsabi-option-do-what-are-the-implications-of-supressi

   Thanks,

     Matt


> Best regards,
>
> Jacob Faibussowitsch
> (Jacob Fai - booss - oh - vitch)
>
>

-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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