Hi!
For the following testcase, B is 16-byte type, containing 8-byte
virtual pointer and 1-byte A member, and C contains two FIELD_DECLs,
one with B type and size of just 8-byte and then a field with type
A and 1-byte size.
The __builtin_clear_padding code was upset about the B typed FIELD_DECL
containing FIELD_DECLs beyond the field size and triggered
assertion failure.
This patch makes it ignore all FIELD_DECLs that are (fully) beyond the sz
passed from the caller (except for the flexible array member
diagnostics that is kept).
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2021-07-26 Jakub Jelinek <ja...@redhat.com>
PR middle-end/101586
* gimple-fold.c (clear_padding_type): Ignore FIELD_DECLs with byte
positions above or equal to sz except for diagnostics of flexible
array members.
* g++.dg/torture/builtin-clear-padding-4.C: New test.
--- gcc/gimple-fold.c.jj 2021-07-20 10:08:09.911687453 +0200
+++ gcc/gimple-fold.c 2021-07-23 12:00:32.212892331 +0200
@@ -4697,6 +4697,8 @@ clear_padding_type (clear_padding_struct
if (fldsz == 0)
continue;
HOST_WIDE_INT pos = int_byte_position (field);
+ if (pos >= sz)
+ continue;
HOST_WIDE_INT bpos
= tree_to_uhwi (DECL_FIELD_BIT_OFFSET (field));
bpos %= BITS_PER_UNIT;
@@ -4772,6 +4774,8 @@ clear_padding_type (clear_padding_struct
else
{
HOST_WIDE_INT pos = int_byte_position (field);
+ if (pos >= sz)
+ continue;
HOST_WIDE_INT fldsz = tree_to_shwi (DECL_SIZE_UNIT (field));
gcc_assert (pos >= 0 && fldsz >= 0 && pos >= cur_pos);
clear_padding_add_padding (buf, pos - cur_pos);
--- gcc/testsuite/g++.dg/torture/builtin-clear-padding-4.C.jj 2021-07-23
12:53:48.372773954 +0200
+++ gcc/testsuite/g++.dg/torture/builtin-clear-padding-4.C 2021-07-23
12:50:41.855114231 +0200
@@ -0,0 +1,44 @@
+// PR middle-end/101586
+
+struct A { char a; };
+struct B : virtual A {};
+struct C : B {};
+struct D : virtual A, C {};
+
+__attribute__((noipa)) A *
+baz (C *p, D *q)
+{
+ if (p)
+ return dynamic_cast <A *> (p);
+ else
+ return dynamic_cast <A *> (q);
+}
+
+void
+foo ()
+{
+ C c;
+ c.a = 42;
+ __builtin_clear_padding (&c);
+ A *p = baz (&c, 0);
+ if (c.a != 42 || p->a != 42)
+ __builtin_abort ();
+}
+
+void
+bar ()
+{
+ D d;
+ d.a = 42;
+ __builtin_clear_padding (&d);
+ A *p = baz (0, &d);
+ if (d.a != 42 || p->a != 42)
+ __builtin_abort ();
+}
+
+int
+main ()
+{
+ foo ();
+ bar ();
+}
Jakub
