FreeChainXenon/gcc
1
0
Fork 0
Code Issues Pull requests Projects Releases Packages Wiki Activity Actions

gimple-fold: Fix up __builtin_clear_padding on classes with virtual inheritence [PR101586]

Browse source 
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).

2021-07-27  Jakub Jelinek  <jakub@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.
This commit is contained in:
Jakub Jelinek 2021-07-27 09:59:37 +02:00
parent 5485e820cd
commit a21bd3cebd
2 changed files with 48 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

4
gcc/gimple-fold.c
View file

@ -4697,6 +4697,8 @@ clear_padding_type (clear_padding_struct *buf, tree type, HOST_WIDE_INT sz)
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 *buf, tree type, HOST_WIDE_INT sz)
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);

44
gcc/testsuite/g++.dg/torture/builtin-clear-padding-4.C Normal file
View file

@ -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 ();
}