On Wed, 17 Aug 2022, Qing Zhao wrote:
> Use array_at_struct_end_p to determine whether the trailing array
> of a structure is flexible array member in __builtin_object_size.
With the discussion about what array_at_struct_end_p actually computes,
is this now the correct utility for __builtin_object_size or should
it use a stricter variant?
> gcc/ChangeLog:
>
> PR tree-optimization/101836
> * tree-object-size.cc (addr_object_size): Use array_at_struct_end_p
> to determine a flexible array member reference.
>
> gcc/testsuite/ChangeLog:
>
> PR tree-optimization/101836
> * gcc.dg/pr101836.c: New test.
> * gcc.dg/pr101836_1.c: New test.
> * gcc.dg/pr101836_2.c: New test.
> * gcc.dg/pr101836_3.c: New test.
> * gcc.dg/pr101836_4.c: New test.
> * gcc.dg/pr101836_5.c: New test.
> * gcc.dg/strict-flex-array-5.c: New test.
> * gcc.dg/strict-flex-array-6.c: New test.
> ---
> gcc/testsuite/gcc.dg/pr101836.c | 60 ++++++++++++++++++++++
> gcc/testsuite/gcc.dg/pr101836_1.c | 60 ++++++++++++++++++++++
> gcc/testsuite/gcc.dg/pr101836_2.c | 60 ++++++++++++++++++++++
> gcc/testsuite/gcc.dg/pr101836_3.c | 60 ++++++++++++++++++++++
> gcc/testsuite/gcc.dg/pr101836_4.c | 60 ++++++++++++++++++++++
> gcc/testsuite/gcc.dg/pr101836_5.c | 60 ++++++++++++++++++++++
> gcc/testsuite/gcc.dg/strict-flex-array-5.c | 60 ++++++++++++++++++++++
> gcc/testsuite/gcc.dg/strict-flex-array-6.c | 60 ++++++++++++++++++++++
> gcc/tree-object-size.cc | 16 +++---
> 9 files changed, 487 insertions(+), 9 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/pr101836.c
> create mode 100644 gcc/testsuite/gcc.dg/pr101836_1.c
> create mode 100644 gcc/testsuite/gcc.dg/pr101836_2.c
> create mode 100644 gcc/testsuite/gcc.dg/pr101836_3.c
> create mode 100644 gcc/testsuite/gcc.dg/pr101836_4.c
> create mode 100644 gcc/testsuite/gcc.dg/pr101836_5.c
> create mode 100644 gcc/testsuite/gcc.dg/strict-flex-array-5.c
> create mode 100644 gcc/testsuite/gcc.dg/strict-flex-array-6.c
>
> diff --git a/gcc/testsuite/gcc.dg/pr101836.c b/gcc/testsuite/gcc.dg/pr101836.c
> new file mode 100644
> index 000000000000..efad02cfe899
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836.c
> @@ -0,0 +1,60 @@
> +/* -fstrict-flex-arrays is aliased with -ftrict-flex-arrays=3, which is the
> + strictest, only [] is treated as flexible array. */
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-arrays" } */
> +
> +#include <stdio.h>
> +
> +#define expect(p, _v) do { \
> + size_t v = _v; \
> + if (p == v) \
> + printf("ok: %s == %zd\n", #p, p); \
> + else \
> + { \
> + printf("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
> + __builtin_abort (); \
> + } \
> +} while (0);
> +
> +struct trailing_array_1 {
> + int a;
> + int b;
> + int c[4];
> +};
> +
> +struct trailing_array_2 {
> + int a;
> + int b;
> + int c[1];
> +};
> +
> +struct trailing_array_3 {
> + int a;
> + int b;
> + int c[0];
> +};
> +struct trailing_array_4 {
> + int a;
> + int b;
> + int c[];
> +};
> +
> +void __attribute__((__noinline__)) stuff(
> + struct trailing_array_1 *normal,
> + struct trailing_array_2 *trailing_1,
> + struct trailing_array_3 *trailing_0,
> + struct trailing_array_4 *trailing_flex)
> +{
> + expect(__builtin_object_size(normal->c, 1), 16);
> + expect(__builtin_object_size(trailing_1->c, 1), 4);
> + expect(__builtin_object_size(trailing_0->c, 1), 0);
> + expect(__builtin_object_size(trailing_flex->c, 1), -1);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + stuff((void *)argv[0], (void *)argv[0], (void *)argv[0], (void
> *)argv[0]);
> +
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/pr101836_1.c
> b/gcc/testsuite/gcc.dg/pr101836_1.c
> new file mode 100644
> index 000000000000..e2931ce1012e
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836_1.c
> @@ -0,0 +1,60 @@
> +/* -fstrict-flex-arrays=3 is the strictest, only [] is treated as
> + flexible array. */
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-arrays=3" } */
> +
> +#include <stdio.h>
> +
> +#define expect(p, _v) do { \
> + size_t v = _v; \
> + if (p == v) \
> + printf("ok: %s == %zd\n", #p, p); \
> + else \
> + { \
> + printf("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
> + __builtin_abort (); \
> + } \
> +} while (0);
> +
> +struct trailing_array_1 {
> + int a;
> + int b;
> + int c[4];
> +};
> +
> +struct trailing_array_2 {
> + int a;
> + int b;
> + int c[1];
> +};
> +
> +struct trailing_array_3 {
> + int a;
> + int b;
> + int c[0];
> +};
> +struct trailing_array_4 {
> + int a;
> + int b;
> + int c[];
> +};
> +
> +void __attribute__((__noinline__)) stuff(
> + struct trailing_array_1 *normal,
> + struct trailing_array_2 *trailing_1,
> + struct trailing_array_3 *trailing_0,
> + struct trailing_array_4 *trailing_flex)
> +{
> + expect(__builtin_object_size(normal->c, 1), 16);
> + expect(__builtin_object_size(trailing_1->c, 1), 4);
> + expect(__builtin_object_size(trailing_0->c, 1), 0);
> + expect(__builtin_object_size(trailing_flex->c, 1), -1);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + stuff((void *)argv[0], (void *)argv[0], (void *)argv[0], (void
> *)argv[0]);
> +
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/pr101836_2.c
> b/gcc/testsuite/gcc.dg/pr101836_2.c
> new file mode 100644
> index 000000000000..78974187721f
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836_2.c
> @@ -0,0 +1,60 @@
> +/* When -fstrict-flex-arrays=2, only [] and [0] are treated as flexiable
> + arrays. */
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-arrays=2" } */
> +
> +#include <stdio.h>
> +
> +#define expect(p, _v) do { \
> + size_t v = _v; \
> + if (p == v) \
> + printf("ok: %s == %zd\n", #p, p); \
> + else \
> + { \
> + printf("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
> + __builtin_abort (); \
> + } \
> +} while (0);
> +
> +struct trailing_array_1 {
> + int a;
> + int b;
> + int c[4];
> +};
> +
> +struct trailing_array_2 {
> + int a;
> + int b;
> + int c[1];
> +};
> +
> +struct trailing_array_3 {
> + int a;
> + int b;
> + int c[0];
> +};
> +struct trailing_array_4 {
> + int a;
> + int b;
> + int c[];
> +};
> +
> +void __attribute__((__noinline__)) stuff(
> + struct trailing_array_1 *normal,
> + struct trailing_array_2 *trailing_1,
> + struct trailing_array_3 *trailing_0,
> + struct trailing_array_4 *trailing_flex)
> +{
> + expect(__builtin_object_size(normal->c, 1), 16);
> + expect(__builtin_object_size(trailing_1->c, 1), 4);
> + expect(__builtin_object_size(trailing_0->c, 1), -1);
> + expect(__builtin_object_size(trailing_flex->c, 1), -1);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + stuff((void *)argv[0], (void *)argv[0], (void *)argv[0], (void
> *)argv[0]);
> +
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/pr101836_3.c
> b/gcc/testsuite/gcc.dg/pr101836_3.c
> new file mode 100644
> index 000000000000..0e69388e81fb
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836_3.c
> @@ -0,0 +1,60 @@
> +/* When -fstrict-flex-arrays=1, [], [0], and [1] are treated as flexible
> + arrays. */
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-arrays=1" } */
> +
> +#include <stdio.h>
> +
> +#define expect(p, _v) do { \
> + size_t v = _v; \
> + if (p == v) \
> + printf("ok: %s == %zd\n", #p, p); \
> + else \
> + { \
> + printf("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
> + __builtin_abort (); \
> + } \
> +} while (0);
> +
> +struct trailing_array_1 {
> + int a;
> + int b;
> + int c[4];
> +};
> +
> +struct trailing_array_2 {
> + int a;
> + int b;
> + int c[1];
> +};
> +
> +struct trailing_array_3 {
> + int a;
> + int b;
> + int c[0];
> +};
> +struct trailing_array_4 {
> + int a;
> + int b;
> + int c[];
> +};
> +
> +void __attribute__((__noinline__)) stuff(
> + struct trailing_array_1 *normal,
> + struct trailing_array_2 *trailing_1,
> + struct trailing_array_3 *trailing_0,
> + struct trailing_array_4 *trailing_flex)
> +{
> + expect(__builtin_object_size(normal->c, 1), 16);
> + expect(__builtin_object_size(trailing_1->c, 1), -1);
> + expect(__builtin_object_size(trailing_0->c, 1), -1);
> + expect(__builtin_object_size(trailing_flex->c, 1), -1);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + stuff((void *)argv[0], (void *)argv[0], (void *)argv[0], (void
> *)argv[0]);
> +
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/pr101836_4.c
> b/gcc/testsuite/gcc.dg/pr101836_4.c
> new file mode 100644
> index 000000000000..e0025aa9a7b5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836_4.c
> @@ -0,0 +1,60 @@
> +/* when -fstrict-flex-arrays=0, all trailing arrays are treated as
> + flexible arrays. */
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-arrays=0" } */
> +
> +#include <stdio.h>
> +
> +#define expect(p, _v) do { \
> + size_t v = _v; \
> + if (p == v) \
> + printf("ok: %s == %zd\n", #p, p); \
> + else \
> + { \
> + printf("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
> + __builtin_abort (); \
> + } \
> +} while (0);
> +
> +struct trailing_array_1 {
> + int a;
> + int b;
> + int c[4];
> +};
> +
> +struct trailing_array_2 {
> + int a;
> + int b;
> + int c[1];
> +};
> +
> +struct trailing_array_3 {
> + int a;
> + int b;
> + int c[0];
> +};
> +struct trailing_array_4 {
> + int a;
> + int b;
> + int c[];
> +};
> +
> +void __attribute__((__noinline__)) stuff(
> + struct trailing_array_1 *normal,
> + struct trailing_array_2 *trailing_1,
> + struct trailing_array_3 *trailing_0,
> + struct trailing_array_4 *trailing_flex)
> +{
> + expect(__builtin_object_size(normal->c, 1), -1);
> + expect(__builtin_object_size(trailing_1->c, 1), -1);
> + expect(__builtin_object_size(trailing_0->c, 1), -1);
> + expect(__builtin_object_size(trailing_flex->c, 1), -1);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + stuff((void *)argv[0], (void *)argv[0], (void *)argv[0], (void
> *)argv[0]);
> +
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/pr101836_5.c
> b/gcc/testsuite/gcc.dg/pr101836_5.c
> new file mode 100644
> index 000000000000..0ad8bbf693ce
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836_5.c
> @@ -0,0 +1,60 @@
> +/* -fno-strict-flex-arrays is aliased to -fstrict-flex-arrays=0,
> + all trailing arrays are treated as flexible array. */
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fno-strict-flex-arrays" } */
> +
> +#include <stdio.h>
> +
> +#define expect(p, _v) do { \
> + size_t v = _v; \
> + if (p == v) \
> + printf("ok: %s == %zd\n", #p, p); \
> + else \
> + { \
> + printf("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
> + __builtin_abort (); \
> + } \
> +} while (0);
> +
> +struct trailing_array_1 {
> + int a;
> + int b;
> + int c[4];
> +};
> +
> +struct trailing_array_2 {
> + int a;
> + int b;
> + int c[1];
> +};
> +
> +struct trailing_array_3 {
> + int a;
> + int b;
> + int c[0];
> +};
> +struct trailing_array_4 {
> + int a;
> + int b;
> + int c[];
> +};
> +
> +void __attribute__((__noinline__)) stuff(
> + struct trailing_array_1 *normal,
> + struct trailing_array_2 *trailing_1,
> + struct trailing_array_3 *trailing_0,
> + struct trailing_array_4 *trailing_flex)
> +{
> + expect(__builtin_object_size(normal->c, 1), -1);
> + expect(__builtin_object_size(trailing_1->c, 1), -1);
> + expect(__builtin_object_size(trailing_0->c, 1), -1);
> + expect(__builtin_object_size(trailing_flex->c, 1), -1);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + stuff((void *)argv[0], (void *)argv[0], (void *)argv[0], (void
> *)argv[0]);
> +
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/strict-flex-array-5.c
> b/gcc/testsuite/gcc.dg/strict-flex-array-5.c
> new file mode 100644
> index 000000000000..e474b9ec43fa
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-5.c
> @@ -0,0 +1,60 @@
> +/* test the combination of attribute strict_flex_arrays and option
> + -fstrict-flex-arrays: when both attribute and option specified,
> + attribute will have higher priority. */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-arrays=3" } */
> +
> +#include <stdio.h>
> +
> +#define expect(p, _v) do { \
> + size_t v = _v; \
> + if (p == v) \
> + printf("ok: %s == %zd\n", #p, p); \
> + else \
> + { \
> + printf("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
> + __builtin_abort (); \
> + } \
> +} while (0);
> +
> +struct trailing_array_1 {
> + int a;
> + int b;
> + int c[4] __attribute__ ((strict_flex_arrays (0)));
> +};
> +
> +struct trailing_array_2 {
> + int a;
> + int b;
> + int c[1] __attribute__ ((strict_flex_arrays (1)));
> +};
> +
> +struct trailing_array_3 {
> + int a;
> + int b;
> + int c[0] __attribute__ ((strict_flex_arrays (2)));
> +};
> +struct trailing_array_4 {
> + int a;
> + int b;
> + int c[];
> +};
> +
> +void __attribute__((__noinline__)) stuff(
> + struct trailing_array_1 *normal,
> + struct trailing_array_2 *trailing_1,
> + struct trailing_array_3 *trailing_0,
> + struct trailing_array_4 *trailing_flex)
> +{
> + expect(__builtin_object_size(normal->c, 1), -1);
> + expect(__builtin_object_size(trailing_1->c, 1), -1);
> + expect(__builtin_object_size(trailing_0->c, 1), -1);
> + expect(__builtin_object_size(trailing_flex->c, 1), -1);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + stuff((void *)argv[0], (void *)argv[0], (void *)argv[0], (void
> *)argv[0]);
> +
> + return 0;
> +}
> diff --git a/gcc/testsuite/gcc.dg/strict-flex-array-6.c
> b/gcc/testsuite/gcc.dg/strict-flex-array-6.c
> new file mode 100644
> index 000000000000..b45e7b32f6d1
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-6.c
> @@ -0,0 +1,60 @@
> +/* test the combination of attribute strict_flex_arrays and option
> + -fstrict-flex-arrays: when both attribute and option specified,
> + attribute will have higher priority. */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-arrays=0" } */
> +
> +#include <stdio.h>
> +
> +#define expect(p, _v) do { \
> + size_t v = _v; \
> + if (p == v) \
> + printf("ok: %s == %zd\n", #p, p); \
> + else \
> + { \
> + printf("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
> + __builtin_abort (); \
> + } \
> +} while (0);
> +
> +struct trailing_array_1 {
> + int a;
> + int b;
> + int c[4] __attribute__ ((strict_flex_arrays (1)));
> +};
> +
> +struct trailing_array_2 {
> + int a;
> + int b;
> + int c[1] __attribute__ ((strict_flex_arrays (2)));
> +};
> +
> +struct trailing_array_3 {
> + int a;
> + int b;
> + int c[0] __attribute__ ((strict_flex_arrays (3)));
> +};
> +struct trailing_array_4 {
> + int a;
> + int b;
> + int c[];
> +};
> +
> +void __attribute__((__noinline__)) stuff(
> + struct trailing_array_1 *normal,
> + struct trailing_array_2 *trailing_1,
> + struct trailing_array_3 *trailing_0,
> + struct trailing_array_4 *trailing_flex)
> +{
> + expect(__builtin_object_size(normal->c, 1), 16);
> + expect(__builtin_object_size(trailing_1->c, 1), 4);
> + expect(__builtin_object_size(trailing_0->c, 1), 0);
> + expect(__builtin_object_size(trailing_flex->c, 1), -1);
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + stuff((void *)argv[0], (void *)argv[0], (void *)argv[0], (void
> *)argv[0]);
> +
> + return 0;
> +}
> diff --git a/gcc/tree-object-size.cc b/gcc/tree-object-size.cc
> index 4eb454a4a33b..1f04cb80fd0a 100644
> --- a/gcc/tree-object-size.cc
> +++ b/gcc/tree-object-size.cc
> @@ -604,9 +604,9 @@ addr_object_size (struct object_size_info *osi,
> const_tree ptr,
> else if (var != pt_var && TREE_CODE (pt_var) == MEM_REF)
> {
> tree v = var;
> - /* For &X->fld, compute object size only if fld isn't the last
> - field, as struct { int i; char c[1]; } is often used instead
> - of flexible array member. */
> + /* For &X->fld, compute object size if fld isn't a flexible array
> + member. */
> + bool is_flexible_array_mem_ref = false;
> while (v && v != pt_var)
> switch (TREE_CODE (v))
> {
> @@ -633,6 +633,7 @@ addr_object_size (struct object_size_info *osi,
> const_tree ptr,
> v = NULL_TREE;
> break;
> }
> + is_flexible_array_mem_ref = array_at_struct_end_p (v);
> while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
> if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
> != UNION_TYPE
> @@ -645,12 +646,9 @@ addr_object_size (struct object_size_info *osi,
> const_tree ptr,
> && TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
> == RECORD_TYPE)
> {
> - tree fld_chain = DECL_CHAIN (TREE_OPERAND (v, 1));
> - for (; fld_chain; fld_chain = DECL_CHAIN (fld_chain))
> - if (TREE_CODE (fld_chain) == FIELD_DECL)
> - break;
> -
> - if (fld_chain)
> + /* compute object size only if v is not a
> + flexible array member. */
> + if (!is_flexible_array_mem_ref)
> {
> v = NULL_TREE;
> break;
>
--
Richard Biener <rguent...@suse.de>
SUSE Software Solutions Germany GmbH, Frankenstrasse 146, 90461 Nuernberg,
Germany; GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman;
HRB 36809 (AG Nuernberg)
