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middle-end: Reject flexible array members in __builtin_clear_padding [PR97943]

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As mentioned in the PR, we currently ICE on flexible array members in
structs and unions during __builtin_clear_padding processing.

Jason said in the PR he'd prefer an error in these cases over forcefully
handling it as [0] arrays (everything is padding then) or consider the
arrays to have as many whole elements as would fit into the tail padding.

So, this patch implements that.

2020-11-25  Jakub Jelinek  <jakub@redhat.com>

	PR middle-end/97943
	* gimple-fold.c (clear_padding_union, clear_padding_type): Error on and
	ignore flexible array member fields.  Ignore fields with
	error_mark_node type.

	* c-c++-common/builtin-clear-padding-2.c: New test.
	* c-c++-common/builtin-clear-padding-3.c: New test.
	* g++.dg/ext/builtin-clear-padding-1.C: New test.
	* gcc.dg/builtin-clear-padding-2.c: New test.
This commit is contained in:
Jakub Jelinek 2020-11-25 10:37:58 +01:00
parent 1e2c9a2761
commit a7285c8659
5 changed files with 85 additions and 1 deletions
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24
gcc/gimple-fold.c
View File

@ -4329,6 +4329,17 @@ clear_padding_union (clear_padding_struct *buf, tree type, HOST_WIDE_INT sz)
for (tree field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
if (TREE_CODE (field) == FIELD_DECL)
{
if (DECL_SIZE_UNIT (field) == NULL_TREE)
{
if (TREE_TYPE (field) == error_mark_node)
continue;
gcc_assert (TREE_CODE (TREE_TYPE (field)) == ARRAY_TYPE
&& !COMPLETE_TYPE_P (TREE_TYPE (field)));
error_at (buf->loc, "flexible array member %qD does not have "
"well defined padding bits for %qs",
field, "__builtin_clear_padding");
continue;
}
HOST_WIDE_INT fldsz = tree_to_shwi (DECL_SIZE_UNIT (field));
gcc_assert (union_buf->size == 0);
union_buf->off = start_off;
@ -4446,11 +4457,12 @@ clear_padding_type (clear_padding_struct *buf, tree type, HOST_WIDE_INT sz)
for (tree field = TYPE_FIELDS (type); field; field = DECL_CHAIN (field))
if (TREE_CODE (field) == FIELD_DECL)
{
tree ftype = TREE_TYPE (field);
if (DECL_BIT_FIELD (field))
{
if (DECL_NAME (field) == NULL_TREE)
continue;
HOST_WIDE_INT fldsz = TYPE_PRECISION (TREE_TYPE (field));
HOST_WIDE_INT fldsz = TYPE_PRECISION (ftype);
if (fldsz == 0)
continue;
HOST_WIDE_INT pos = int_byte_position (field);
@ -4513,6 +4525,16 @@ clear_padding_type (clear_padding_struct *buf, tree type, HOST_WIDE_INT sz)
}
}
}
else if (DECL_SIZE_UNIT (field) == NULL_TREE)
{
if (ftype == error_mark_node)
continue;
gcc_assert (TREE_CODE (ftype) == ARRAY_TYPE
&& !COMPLETE_TYPE_P (ftype));
error_at (buf->loc, "flexible array member %qD does not have "
"well defined padding bits for %qs",
field, "__builtin_clear_padding");
}
else
{
HOST_WIDE_INT pos = int_byte_position (field);

17
gcc/testsuite/c-c++-common/builtin-clear-padding-2.c Normal file
View File

@ -0,0 +1,17 @@
/* PR middle-end/97943 */
/* { dg-do compile } */
/* { dg-options "" } */
struct S { int a; char b[] __attribute__((aligned (2 * sizeof (int)))); };
struct T { int a; struct S b; };
union U { int a; struct S b; };
struct V { int a; union U b; };
void
foo (struct S *s, struct T *t, union U *u, struct V *v)
{
__builtin_clear_padding (s); /* { dg-error "flexible array member '(S::)?b' does not have well defined padding bits for '__builtin_clear_padding'" } */
__builtin_clear_padding (t); /* { dg-error "flexible array member '(S::)?b' does not have well defined padding bits for '__builtin_clear_padding'" } */
__builtin_clear_padding (u); /* { dg-error "flexible array member '(S::)?b' does not have well defined padding bits for '__builtin_clear_padding'" } */
__builtin_clear_padding (v); /* { dg-error "flexible array member '(S::)?b' does not have well defined padding bits for '__builtin_clear_padding'" } */
}

15
gcc/testsuite/c-c++-common/builtin-clear-padding-3.c Normal file
View File

@ -0,0 +1,15 @@
/* PR middle-end/97943 */
/* { dg-do compile } */
/* { dg-options "" } */
union U { int a; char b[] __attribute__((aligned (2 * sizeof (int)))); }; /* { dg-error "flexible array member in union" } */
struct V { int a; union U b; };
struct W { int a; union U b; int c; };
void
foo (union U *u, struct V *v, struct W *w)
{
__builtin_clear_padding (u);
__builtin_clear_padding (v);
__builtin_clear_padding (w);
}

15
gcc/testsuite/g++.dg/ext/builtin-clear-padding-1.C Normal file
View File

@ -0,0 +1,15 @@
// PR middle-end/97943
// { dg-do compile }
// { dg-options "" }
struct S { int a; char b[] __attribute__((aligned (2 * sizeof (int)))); }; // { dg-error "flexible array member 'S::b' not at end of 'struct \[TV]'" }
struct T { int a; struct S b; int c; }; // { dg-message "next member 'int T::c' declared here|in the definition of 'struct T'" }
union U { int a; struct S b; };
struct V { int a; union U b; int : 15; int c; }; // { dg-message "next member 'int V::c' declared here|in the definition of 'struct V'" }
void
foo (struct T *t, struct V *v)
{
__builtin_clear_padding (t); // { dg-error "flexible array member 'S::b' does not have well defined padding bits for '__builtin_clear_padding'" }
__builtin_clear_padding (v); // { dg-error "flexible array member 'S::b' does not have well defined padding bits for '__builtin_clear_padding'" }
}

15
gcc/testsuite/gcc.dg/builtin-clear-padding-2.c Normal file
View File

@ -0,0 +1,15 @@
/* PR middle-end/97943 */
/* { dg-do compile } */
/* { dg-options "" } */
struct S { int a; char b[] __attribute__((aligned (2 * sizeof (int)))); };
struct T { int a; struct S b; int c; };
union U { int a; struct S b; };
struct V { int a; union U b; int : 15; int c; };
void
foo (struct T *t, struct V *v)
{
__builtin_clear_padding (t); /* { dg-error "flexible array member 'b' does not have well defined padding bits for '__builtin_clear_padding'" } */
__builtin_clear_padding (v); /* { dg-error "flexible array member 'b' does not have well defined padding bits for '__builtin_clear_padding'" } */
}