https://gcc.gnu.org/bugzilla/show_bug.cgi?id=71912
Martin Sebor <msebor at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |ASSIGNED
Last reconfirmed| |2016-07-18
Known to work| |5.4.0
Assignee|unassigned at gcc dot gnu.org |msebor at gcc dot
gnu.org
Summary|flexible array in union |[6/7 regression] flexible
| |array in struct in union
| |rejected
Ever confirmed|0 |1
Known to fail| |6.1.0, 7.0
--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
I confirm the code in the test case is meant to be accepted by G++ for
compatibility with GCC but is rejected due to a bug in the find_flexarrays
function in class.c.
That said, it's not completely clear that the code is valid according to the C
definition of a flexible array member:
As a special case, the last element of a structure with more than one named
member may have an incomplete array type; this is called a /flexible array
member/.
Although C doesn't define the term element, I think it means the last declared
subobject of an object.
In the test case, neither of the two flexible array members is the last element
of struct xyyzy (the last element is the subobject u). Within the member u of
struct xyyzy, the flexible array member f.s is not the last element of the
structure xyyzy (b.t is the last element).
Even though GCC with -Wpedantic silently accepts the equivalent definition of
struct xyyzy, it issues a diagnostic for baz supporting the interpretation
above:
warning: invalid use of structure with flexible array member
Since the struct definitions are equivalent, it seems that either they both
should be diagnosed or neither should be.
