https://gcc.gnu.org/bugzilla/show_bug.cgi?id=64789
Bug ID: 64789
Summary: gcc generates unreliable code on arm with
-mstructure-size-boundary=32
Product: gcc
Version: 4.8.3
Status: RESOLVED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: mittorn at sibmail dot com
Status: RESOLVED
Resolution: INVALID
After rebuilding many of system libraries with -mstructure-size-boundary=32 i
found that fsck.fat does not work propertly and all gtk applications does not
correctly handle input and xfce4-desktop shows icons with wrong coordinates
After rebuilding dosfstools and libX11 problem was solved
--- Comment #1 from Richard Earnshaw <rearnsha at gcc dot gnu.org> ---
-mstructure-size-boundary (with size != 8) is really intended for use only with
the old ABI and as such should probably be considered deprecated in any
environment that does not use that as the default. Note that changing the
structure layout rules is an ABI change and thus generates a data layout that
is not interoperable with programs built to the default rules. The entire
system will need to be rebuilt with that setting in order to avoid the sorts of
issues you describe.
Additionally, although over-alignment of structures is permitted by the C
language, many software packages fail to take this portability constraint into
account and assume that a structure will be no more aligned than its most
aligned element (and no larger than the next multiple of that alignment that is
larger than that required to hold all the elements).
For example,
struct s {
char a;
};
will have size 1 and alignment 1 with -mstructure-size-boundary=8, but size 4
and alignment 4 with -mstructure-size-boundary=32. This becomes significant
when such structures are contained within other structures.
Finally, you haven't provided a testcase. So in the absence of any real
evidence that this is a compiler problem, I'm closing as invalid.
