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Subject: [Bug fortran/56293] Segfault when trying to access pass-by-reference value of a not-word-aligned REAL(16) /  -fno-align-commons
Date: Tue, 12 Feb 2013 13:07:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D56293

--- Comment #5 from Tobias Burnus <burnus at gcc dot gnu.org> 2013-02-12 13=
:07:10 UTC ---
Some tests with ifort, which by default uses unaligned commons: The first t=
est
case works, i.e. I/O with the unaligned "p" works. However, if one calls a =
user
procedure ("call foo(p)"), it segfaults.


Possible solutions:

a) Copy-in/copy-out around procedure calls - which is fun with large arrays.

b) Require the user to annotate the functions to possibly accept unaligned
input =E2=80=93 or do so automatically. (With all the fun of third-party li=
braries like
LAPACK, BLAS, ...)

c) Simply deprecating the  -fno-align-commons flag, improving the wording of
the diagnostic and the description in the man page.

Somehow, I am in favour of (c).

The question is also whether one can construct a fully standard-conform exa=
mple
which fails without -fno-align-commons =E2=80=93 and whether some real-worl=
d code uses
COMMON in a way that would fails with alignments/padding.