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

[Jacob Faibussowitsch]

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?

Best regards,

Jacob Faibussowitsch
(Jacob Fai - booss - oh - vitch)

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