https://gcc.gnu.org/bugzilla/show_bug.cgi?id=96495
Paul Thomas <pault at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Assignee|unassigned at gcc dot gnu.org |pault at gcc dot gnu.org
CC| |pault at gcc dot gnu.org
Status|UNCONFIRMED |NEW
Ever confirmed|0 |1
Last reconfirmed| |2020-08-28
--- Comment #3 from Paul Thomas <pault at gcc dot gnu.org> ---
Hi Paul,
Thank you very much for this report. The cause if the segfault is revealed by
using the option -fdump-tree-original.
The assignment
g = g .binaryElemental. (f .binary. f)
is rendered as:
{
struct foo D.4200;
D.4200 = foo_sub_foo (&f, &f); /* Outside the scalarization loop. */
{ /* ...as it should be :-) */
integer(kind=8) S.30;
S.30 = 1;
while (1)
{
if (S.30 > 2) goto L.21;
{
struct foo * D.4202;
struct foo D.4203;
D.4202 = &D.4200;
D.4203 = g[S.30 + -1];
g[S.30 + -1] = foo_add_foo (&g[S.30 + -1], D.4202);
if ((integer(kind=4)[0:] * restrict) D.4203.j.data != 0B)
{
__builtin_free ((void *) D.4203.j.data);
(integer(kind=4)[0:] * restrict) D.4203.j.data = 0B;
}
/* Here the 'j' component of the scalar temporary is
deallocated on the first pass through the scalarization
loop so that the second pass through the loop attempts
to read a null address. /*
if ((integer(kind=4)[0:] * restrict) D.4202->j.data != 0B)
{
__builtin_free ((void *) D.4202->j.data);
(integer(kind=4)[0:] * restrict) D.4202->j.data = 0B;
}
}
S.30 = S.30 + 1;
}
L.21:;
}
}
As you can see from the comments, the garbage collection mechanism is overdoing
it and the deallocation of D.4202->j should be done outside the scalarization
loop.
I presume that you have already found the workaround:
tmp = (f .binary. f)
g = g .binaryElemental. tmp
where tmp is a scalar of type 'foo'?
This does the right thing...
{
struct foo D.4201;
D.4201 = tmp;
tmp = foo_sub_foo (&f, &f);
if ((integer(kind=4)[0:] * restrict) D.4201.j.data != 0B)
{
__builtin_free ((void *) D.4201.j.data);
(integer(kind=4)[0:] * restrict) D.4201.j.data = 0B;
}
}
{
struct foo * D.4202;
D.4202 = &tmp;
{
integer(kind=8) S.30;
S.30 = 1;
while (1)
{
if (S.30 > 2) goto L.21;
{
struct foo D.4204;
D.4204 = g[S.30 + -1];
g[S.30 + -1] = foo_add_foo (&g[S.30 + -1], D.4202);
if ((integer(kind=4)[0:] * restrict) D.4204.j.data != 0B)
{
__builtin_free ((void *) D.4204.j.data);
(integer(kind=4)[0:] * restrict) D.4204.j.data = 0B;
}
}
S.30 = S.30 + 1;
}
L.21:;
}
}
}
}
I will work on this in the coming days.
Best regards
Paul
