[GCC13,V2,2/2] Add a new option -fstrict-flex-array[=n] and attribute strict_flex_array(n) and use it in PR101836

  From a09f39ded462611286a44d9e8273de8342673ba2 Mon Sep 17 00:00:00 2001
From: Qing Zhao <qing.zhao@oracle.com>
Date: Mon, 18 Jul 2022 18:12:26 +0000
Subject: [PATCH 2/2] Use new flag DECL_NOT_FLEXARRAY in __builtin_object_size
[PR101836]

Use new flag DECL_NOT_FLEXARRAY to determine whether the trailing array
of a structure is flexible array member in __builtin_object_size.

gcc/ChangeLog:

	PR tree-optimization/101836
	* tree-object-size.cc (addr_object_size): Use array_at_struct_end_p
	and DECL_NOT_FLEXARRAY 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-2.c: New test.
	* gcc.dg/strict-flex-array-3.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-2.c | 60 ++++++++++++++++++++++
gcc/testsuite/gcc.dg/strict-flex-array-3.c | 60 ++++++++++++++++++++++
gcc/tree-object-size.cc                    | 18 +++----
9 files changed, 489 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-2.c
create mode 100644 gcc/testsuite/gcc.dg/strict-flex-array-3.c
  

On Tue, 19 Jul 2022, Qing Zhao wrote:

> From a09f39ded462611286a44d9e8273de8342673ba2 Mon Sep 17 00:00:00 2001
> From: Qing Zhao <qing.zhao@oracle.com>
> Date: Mon, 18 Jul 2022 18:12:26 +0000
> Subject: [PATCH 2/2] Use new flag DECL_NOT_FLEXARRAY in __builtin_object_size
> [PR101836]
> 
> Use new flag DECL_NOT_FLEXARRAY to determine whether the trailing array
> of a structure is flexible array member in __builtin_object_size.
> 
> gcc/ChangeLog:
> 
> 	PR tree-optimization/101836
> 	* tree-object-size.cc (addr_object_size): Use array_at_struct_end_p
> 	and DECL_NOT_FLEXARRAY 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-2.c: New test.
> 	* gcc.dg/strict-flex-array-3.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-2.c | 60 ++++++++++++++++++++++
> gcc/testsuite/gcc.dg/strict-flex-array-3.c | 60 ++++++++++++++++++++++
> gcc/tree-object-size.cc                    | 18 +++----
> 9 files changed, 489 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-2.c
> create mode 100644 gcc/testsuite/gcc.dg/strict-flex-array-3.c
> 
> diff --git a/gcc/testsuite/gcc.dg/pr101836.c b/gcc/testsuite/gcc.dg/pr101836.c
> new file mode 100644
> index 00000000000..e5b4e5160a4
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836.c
> @@ -0,0 +1,60 @@
> +/* -fstrict-flex-array is aliased with -ftrict-flex-array=3, which is the
> +   strictest, only [] is treated as flexible array.  */ 
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-array" } */
> +
> +#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 00000000000..30ea20427a5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836_1.c
> @@ -0,0 +1,60 @@
> +/* -fstrict-flex-array=3 is the strictest, only [] is treated as
> +   flexible array.  */ 
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..ebbe88f433c
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836_2.c
> @@ -0,0 +1,60 @@
> +/* When -fstrict-flex-array=2, only [] and [0] are treated as flexiable
> +   arrays.  */
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..d4ba0afe5bc
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836_3.c
> @@ -0,0 +1,60 @@
> +/* When -fstrict-flex-array=1, [], [0], and [1] are treated as flexible
> +   arrays.  */
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..b10d3ce312d
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836_4.c
> @@ -0,0 +1,60 @@
> +/* when -fstrict-flex-array=0, all trailing arrays are treated as
> +   flexible arrays.  */
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..2f6b5f7ae1f
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/pr101836_5.c
> @@ -0,0 +1,60 @@
> +/* -fno-strict-flex-array is aliased to -fstrict-flex-array=0,
> +   all trailing arrays are treated as flexible array.  */
> +/* PR tree-optimization/101836 */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fno-strict-flex-array" } */
> +
> +#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-2.c b/gcc/testsuite/gcc.dg/strict-flex-array-2.c
> new file mode 100644
> index 00000000000..326ddcfeda5
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-2.c
> @@ -0,0 +1,60 @@
> +/* test the combination of attribute strict_flex_array and option
> +   -fstrict-flex-array: when both attribute and option specified,
> +   attribute will have higher priority.  */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-array=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_array (0)));
> +};
> +
> +struct trailing_array_2 {
> +    int a;
> +    int b;
> +    int c[1] __attribute__ ((strict_flex_array (1)));
> +};
> +
> +struct trailing_array_3 {
> +    int a;
> +    int b;
> +    int c[0] __attribute__ ((strict_flex_array (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-3.c b/gcc/testsuite/gcc.dg/strict-flex-array-3.c
> new file mode 100644
> index 00000000000..990c5bb6223
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-3.c
> @@ -0,0 +1,60 @@
> +/* test the combination of attribute strict_flex_array and option
> +   -fstrict-flex-array: when both attribute and option specified,
> +   attribute will have higher priority.  */
> +/* { dg-do run } */
> +/* { dg-options "-O2 -fstrict-flex-array=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_array (1)));
> +};
> +
> +struct trailing_array_2 {
> +    int a;
> +    int b;
> +    int c[1] __attribute__ ((strict_flex_array (2)));
> +};
> +
> +struct trailing_array_3 {
> +    int a;
> +    int b;
> +    int c[0] __attribute__ ((strict_flex_array (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 4eb454a4a33..90710ecba72 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.  */
> +	      bool is_flexible_array_mem_ref = false;
> +	      /* For &X->fld, compute object size if fld isn't a flexible array
> +		 member.  */
> 	      while (v && v != pt_var)
> 		switch (TREE_CODE (v))
> 		  {
> @@ -633,6 +633,9 @@ 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)
> +			&& !DECL_NOT_FLEXARRAY (TREE_OPERAND (v, 1));

As said in the review for the first patch array_at_struct_end_p should
check DECL_NOT_FLEXARRAY.

OK with removing the extra check here.

> 		    while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
> 		      if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
> 			  != UNION_TYPE
> @@ -645,12 +648,9 @@ 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;
>
  

> On Jul 28, 2022, at 3:28 AM, Richard Biener <rguenther@suse.de> wrote:
> 
> On Tue, 19 Jul 2022, Qing Zhao wrote:
> 
>> From a09f39ded462611286a44d9e8273de8342673ba2 Mon Sep 17 00:00:00 2001
>> From: Qing Zhao <qing.zhao@oracle.com>
>> Date: Mon, 18 Jul 2022 18:12:26 +0000
>> Subject: [PATCH 2/2] Use new flag DECL_NOT_FLEXARRAY in __builtin_object_size
>> [PR101836]
>> 
>> Use new flag DECL_NOT_FLEXARRAY to determine whether the trailing array
>> of a structure is flexible array member in __builtin_object_size.
>> 
>> gcc/ChangeLog:
>> 
>> 	PR tree-optimization/101836
>> 	* tree-object-size.cc (addr_object_size): Use array_at_struct_end_p
>> 	and DECL_NOT_FLEXARRAY 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-2.c: New test.
>> 	* gcc.dg/strict-flex-array-3.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-2.c | 60 ++++++++++++++++++++++
>> gcc/testsuite/gcc.dg/strict-flex-array-3.c | 60 ++++++++++++++++++++++
>> gcc/tree-object-size.cc                    | 18 +++----
>> 9 files changed, 489 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-2.c
>> create mode 100644 gcc/testsuite/gcc.dg/strict-flex-array-3.c
>> 
>> diff --git a/gcc/testsuite/gcc.dg/pr101836.c b/gcc/testsuite/gcc.dg/pr101836.c
>> new file mode 100644
>> index 00000000000..e5b4e5160a4
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/pr101836.c
>> @@ -0,0 +1,60 @@
>> +/* -fstrict-flex-array is aliased with -ftrict-flex-array=3, which is the
>> +   strictest, only [] is treated as flexible array.  */ 
>> +/* PR tree-optimization/101836 */
>> +/* { dg-do run } */
>> +/* { dg-options "-O2 -fstrict-flex-array" } */
>> +
>> +#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 00000000000..30ea20427a5
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/pr101836_1.c
>> @@ -0,0 +1,60 @@
>> +/* -fstrict-flex-array=3 is the strictest, only [] is treated as
>> +   flexible array.  */ 
>> +/* PR tree-optimization/101836 */
>> +/* { dg-do run } */
>> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..ebbe88f433c
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/pr101836_2.c
>> @@ -0,0 +1,60 @@
>> +/* When -fstrict-flex-array=2, only [] and [0] are treated as flexiable
>> +   arrays.  */
>> +/* PR tree-optimization/101836 */
>> +/* { dg-do run } */
>> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..d4ba0afe5bc
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/pr101836_3.c
>> @@ -0,0 +1,60 @@
>> +/* When -fstrict-flex-array=1, [], [0], and [1] are treated as flexible
>> +   arrays.  */
>> +/* PR tree-optimization/101836 */
>> +/* { dg-do run } */
>> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..b10d3ce312d
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/pr101836_4.c
>> @@ -0,0 +1,60 @@
>> +/* when -fstrict-flex-array=0, all trailing arrays are treated as
>> +   flexible arrays.  */
>> +/* PR tree-optimization/101836 */
>> +/* { dg-do run } */
>> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..2f6b5f7ae1f
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/pr101836_5.c
>> @@ -0,0 +1,60 @@
>> +/* -fno-strict-flex-array is aliased to -fstrict-flex-array=0,
>> +   all trailing arrays are treated as flexible array.  */
>> +/* PR tree-optimization/101836 */
>> +/* { dg-do run } */
>> +/* { dg-options "-O2 -fno-strict-flex-array" } */
>> +
>> +#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-2.c b/gcc/testsuite/gcc.dg/strict-flex-array-2.c
>> new file mode 100644
>> index 00000000000..326ddcfeda5
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-2.c
>> @@ -0,0 +1,60 @@
>> +/* test the combination of attribute strict_flex_array and option
>> +   -fstrict-flex-array: when both attribute and option specified,
>> +   attribute will have higher priority.  */
>> +/* { dg-do run } */
>> +/* { dg-options "-O2 -fstrict-flex-array=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_array (0)));
>> +};
>> +
>> +struct trailing_array_2 {
>> +    int a;
>> +    int b;
>> +    int c[1] __attribute__ ((strict_flex_array (1)));
>> +};
>> +
>> +struct trailing_array_3 {
>> +    int a;
>> +    int b;
>> +    int c[0] __attribute__ ((strict_flex_array (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-3.c b/gcc/testsuite/gcc.dg/strict-flex-array-3.c
>> new file mode 100644
>> index 00000000000..990c5bb6223
>> --- /dev/null
>> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-3.c
>> @@ -0,0 +1,60 @@
>> +/* test the combination of attribute strict_flex_array and option
>> +   -fstrict-flex-array: when both attribute and option specified,
>> +   attribute will have higher priority.  */
>> +/* { dg-do run } */
>> +/* { dg-options "-O2 -fstrict-flex-array=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_array (1)));
>> +};
>> +
>> +struct trailing_array_2 {
>> +    int a;
>> +    int b;
>> +    int c[1] __attribute__ ((strict_flex_array (2)));
>> +};
>> +
>> +struct trailing_array_3 {
>> +    int a;
>> +    int b;
>> +    int c[0] __attribute__ ((strict_flex_array (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 4eb454a4a33..90710ecba72 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.  */
>> +	      bool is_flexible_array_mem_ref = false;
>> +	      /* For &X->fld, compute object size if fld isn't a flexible array
>> +		 member.  */
>> 	      while (v && v != pt_var)
>> 		switch (TREE_CODE (v))
>> 		  {
>> @@ -633,6 +633,9 @@ 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)
>> +			&& !DECL_NOT_FLEXARRAY (TREE_OPERAND (v, 1));
> 
> As said in the review for the first patch array_at_struct_end_p should
> check DECL_NOT_FLEXARRAY.
Okay.

Then,  should we change the name of “array_at_struct_end_p” to a more descriptive name, for example,”flexible_array_member_p”? Otherwise,
It’s really confusing.


> 
> OK with removing the extra check here.

Okay.


thanks.

Qing
> 
>> 		    while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
>> 		      if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
>> 			  != UNION_TYPE
>> @@ -645,12 +648,9 @@ 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 <rguenther@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)
  

On Fri, 29 Jul 2022, Qing Zhao wrote:

> 
> 
> > On Jul 28, 2022, at 3:28 AM, Richard Biener <rguenther@suse.de> wrote:
> > 
> > On Tue, 19 Jul 2022, Qing Zhao wrote:
> > 
> >> From a09f39ded462611286a44d9e8273de8342673ba2 Mon Sep 17 00:00:00 2001
> >> From: Qing Zhao <qing.zhao@oracle.com>
> >> Date: Mon, 18 Jul 2022 18:12:26 +0000
> >> Subject: [PATCH 2/2] Use new flag DECL_NOT_FLEXARRAY in __builtin_object_size
> >> [PR101836]
> >> 
> >> Use new flag DECL_NOT_FLEXARRAY to determine whether the trailing array
> >> of a structure is flexible array member in __builtin_object_size.
> >> 
> >> gcc/ChangeLog:
> >> 
> >> 	PR tree-optimization/101836
> >> 	* tree-object-size.cc (addr_object_size): Use array_at_struct_end_p
> >> 	and DECL_NOT_FLEXARRAY 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-2.c: New test.
> >> 	* gcc.dg/strict-flex-array-3.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-2.c | 60 ++++++++++++++++++++++
> >> gcc/testsuite/gcc.dg/strict-flex-array-3.c | 60 ++++++++++++++++++++++
> >> gcc/tree-object-size.cc                    | 18 +++----
> >> 9 files changed, 489 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-2.c
> >> create mode 100644 gcc/testsuite/gcc.dg/strict-flex-array-3.c
> >> 
> >> diff --git a/gcc/testsuite/gcc.dg/pr101836.c b/gcc/testsuite/gcc.dg/pr101836.c
> >> new file mode 100644
> >> index 00000000000..e5b4e5160a4
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/pr101836.c
> >> @@ -0,0 +1,60 @@
> >> +/* -fstrict-flex-array is aliased with -ftrict-flex-array=3, which is the
> >> +   strictest, only [] is treated as flexible array.  */ 
> >> +/* PR tree-optimization/101836 */
> >> +/* { dg-do run } */
> >> +/* { dg-options "-O2 -fstrict-flex-array" } */
> >> +
> >> +#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 00000000000..30ea20427a5
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/pr101836_1.c
> >> @@ -0,0 +1,60 @@
> >> +/* -fstrict-flex-array=3 is the strictest, only [] is treated as
> >> +   flexible array.  */ 
> >> +/* PR tree-optimization/101836 */
> >> +/* { dg-do run } */
> >> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..ebbe88f433c
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/pr101836_2.c
> >> @@ -0,0 +1,60 @@
> >> +/* When -fstrict-flex-array=2, only [] and [0] are treated as flexiable
> >> +   arrays.  */
> >> +/* PR tree-optimization/101836 */
> >> +/* { dg-do run } */
> >> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..d4ba0afe5bc
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/pr101836_3.c
> >> @@ -0,0 +1,60 @@
> >> +/* When -fstrict-flex-array=1, [], [0], and [1] are treated as flexible
> >> +   arrays.  */
> >> +/* PR tree-optimization/101836 */
> >> +/* { dg-do run } */
> >> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..b10d3ce312d
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/pr101836_4.c
> >> @@ -0,0 +1,60 @@
> >> +/* when -fstrict-flex-array=0, all trailing arrays are treated as
> >> +   flexible arrays.  */
> >> +/* PR tree-optimization/101836 */
> >> +/* { dg-do run } */
> >> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..2f6b5f7ae1f
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/pr101836_5.c
> >> @@ -0,0 +1,60 @@
> >> +/* -fno-strict-flex-array is aliased to -fstrict-flex-array=0,
> >> +   all trailing arrays are treated as flexible array.  */
> >> +/* PR tree-optimization/101836 */
> >> +/* { dg-do run } */
> >> +/* { dg-options "-O2 -fno-strict-flex-array" } */
> >> +
> >> +#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-2.c b/gcc/testsuite/gcc.dg/strict-flex-array-2.c
> >> new file mode 100644
> >> index 00000000000..326ddcfeda5
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-2.c
> >> @@ -0,0 +1,60 @@
> >> +/* test the combination of attribute strict_flex_array and option
> >> +   -fstrict-flex-array: when both attribute and option specified,
> >> +   attribute will have higher priority.  */
> >> +/* { dg-do run } */
> >> +/* { dg-options "-O2 -fstrict-flex-array=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_array (0)));
> >> +};
> >> +
> >> +struct trailing_array_2 {
> >> +    int a;
> >> +    int b;
> >> +    int c[1] __attribute__ ((strict_flex_array (1)));
> >> +};
> >> +
> >> +struct trailing_array_3 {
> >> +    int a;
> >> +    int b;
> >> +    int c[0] __attribute__ ((strict_flex_array (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-3.c b/gcc/testsuite/gcc.dg/strict-flex-array-3.c
> >> new file mode 100644
> >> index 00000000000..990c5bb6223
> >> --- /dev/null
> >> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-3.c
> >> @@ -0,0 +1,60 @@
> >> +/* test the combination of attribute strict_flex_array and option
> >> +   -fstrict-flex-array: when both attribute and option specified,
> >> +   attribute will have higher priority.  */
> >> +/* { dg-do run } */
> >> +/* { dg-options "-O2 -fstrict-flex-array=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_array (1)));
> >> +};
> >> +
> >> +struct trailing_array_2 {
> >> +    int a;
> >> +    int b;
> >> +    int c[1] __attribute__ ((strict_flex_array (2)));
> >> +};
> >> +
> >> +struct trailing_array_3 {
> >> +    int a;
> >> +    int b;
> >> +    int c[0] __attribute__ ((strict_flex_array (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 4eb454a4a33..90710ecba72 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.  */
> >> +	      bool is_flexible_array_mem_ref = false;
> >> +	      /* For &X->fld, compute object size if fld isn't a flexible array
> >> +		 member.  */
> >> 	      while (v && v != pt_var)
> >> 		switch (TREE_CODE (v))
> >> 		  {
> >> @@ -633,6 +633,9 @@ 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)
> >> +			&& !DECL_NOT_FLEXARRAY (TREE_OPERAND (v, 1));
> > 
> > As said in the review for the first patch array_at_struct_end_p should
> > check DECL_NOT_FLEXARRAY.
> Okay.
> 
> Then, should we change the name of “array_at_struct_end_p” to a more 
> descriptive name, for example,”flexible_array_member_p”? Otherwise, It’s 
> really confusing.

It has been that way since forever, so please don't (at least not as
part of this series).

> 
> 
> > 
> > OK with removing the extra check here.
> 
> Okay.
> 
> 
> thanks.
> 
> Qing
> > 
> >> 		    while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
> >> 		      if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
> >> 			  != UNION_TYPE
> >> @@ -645,12 +648,9 @@ 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 <rguenther@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)
> 
>
  

> On Aug 1, 2022, at 3:13 AM, Richard Biener <rguenther@suse.de> wrote:
> 
> On Fri, 29 Jul 2022, Qing Zhao wrote:
> 
>> 
>> 
>>> On Jul 28, 2022, at 3:28 AM, Richard Biener <rguenther@suse.de> wrote:
>>> 
>>> On Tue, 19 Jul 2022, Qing Zhao wrote:
>>> 
>>>> From a09f39ded462611286a44d9e8273de8342673ba2 Mon Sep 17 00:00:00 2001
>>>> From: Qing Zhao <qing.zhao@oracle.com>
>>>> Date: Mon, 18 Jul 2022 18:12:26 +0000
>>>> Subject: [PATCH 2/2] Use new flag DECL_NOT_FLEXARRAY in __builtin_object_size
>>>> [PR101836]
>>>> 
>>>> Use new flag DECL_NOT_FLEXARRAY to determine whether the trailing array
>>>> of a structure is flexible array member in __builtin_object_size.
>>>> 
>>>> gcc/ChangeLog:
>>>> 
>>>> 	PR tree-optimization/101836
>>>> 	* tree-object-size.cc (addr_object_size): Use array_at_struct_end_p
>>>> 	and DECL_NOT_FLEXARRAY 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-2.c: New test.
>>>> 	* gcc.dg/strict-flex-array-3.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-2.c | 60 ++++++++++++++++++++++
>>>> gcc/testsuite/gcc.dg/strict-flex-array-3.c | 60 ++++++++++++++++++++++
>>>> gcc/tree-object-size.cc                    | 18 +++----
>>>> 9 files changed, 489 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-2.c
>>>> create mode 100644 gcc/testsuite/gcc.dg/strict-flex-array-3.c
>>>> 
>>>> diff --git a/gcc/testsuite/gcc.dg/pr101836.c b/gcc/testsuite/gcc.dg/pr101836.c
>>>> new file mode 100644
>>>> index 00000000000..e5b4e5160a4
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/pr101836.c
>>>> @@ -0,0 +1,60 @@
>>>> +/* -fstrict-flex-array is aliased with -ftrict-flex-array=3, which is the
>>>> +   strictest, only [] is treated as flexible array.  */ 
>>>> +/* PR tree-optimization/101836 */
>>>> +/* { dg-do run } */
>>>> +/* { dg-options "-O2 -fstrict-flex-array" } */
>>>> +
>>>> +#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 00000000000..30ea20427a5
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/pr101836_1.c
>>>> @@ -0,0 +1,60 @@
>>>> +/* -fstrict-flex-array=3 is the strictest, only [] is treated as
>>>> +   flexible array.  */ 
>>>> +/* PR tree-optimization/101836 */
>>>> +/* { dg-do run } */
>>>> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..ebbe88f433c
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/pr101836_2.c
>>>> @@ -0,0 +1,60 @@
>>>> +/* When -fstrict-flex-array=2, only [] and [0] are treated as flexiable
>>>> +   arrays.  */
>>>> +/* PR tree-optimization/101836 */
>>>> +/* { dg-do run } */
>>>> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..d4ba0afe5bc
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/pr101836_3.c
>>>> @@ -0,0 +1,60 @@
>>>> +/* When -fstrict-flex-array=1, [], [0], and [1] are treated as flexible
>>>> +   arrays.  */
>>>> +/* PR tree-optimization/101836 */
>>>> +/* { dg-do run } */
>>>> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..b10d3ce312d
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/pr101836_4.c
>>>> @@ -0,0 +1,60 @@
>>>> +/* when -fstrict-flex-array=0, all trailing arrays are treated as
>>>> +   flexible arrays.  */
>>>> +/* PR tree-optimization/101836 */
>>>> +/* { dg-do run } */
>>>> +/* { dg-options "-O2 -fstrict-flex-array=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 00000000000..2f6b5f7ae1f
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/pr101836_5.c
>>>> @@ -0,0 +1,60 @@
>>>> +/* -fno-strict-flex-array is aliased to -fstrict-flex-array=0,
>>>> +   all trailing arrays are treated as flexible array.  */
>>>> +/* PR tree-optimization/101836 */
>>>> +/* { dg-do run } */
>>>> +/* { dg-options "-O2 -fno-strict-flex-array" } */
>>>> +
>>>> +#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-2.c b/gcc/testsuite/gcc.dg/strict-flex-array-2.c
>>>> new file mode 100644
>>>> index 00000000000..326ddcfeda5
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-2.c
>>>> @@ -0,0 +1,60 @@
>>>> +/* test the combination of attribute strict_flex_array and option
>>>> +   -fstrict-flex-array: when both attribute and option specified,
>>>> +   attribute will have higher priority.  */
>>>> +/* { dg-do run } */
>>>> +/* { dg-options "-O2 -fstrict-flex-array=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_array (0)));
>>>> +};
>>>> +
>>>> +struct trailing_array_2 {
>>>> +    int a;
>>>> +    int b;
>>>> +    int c[1] __attribute__ ((strict_flex_array (1)));
>>>> +};
>>>> +
>>>> +struct trailing_array_3 {
>>>> +    int a;
>>>> +    int b;
>>>> +    int c[0] __attribute__ ((strict_flex_array (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-3.c b/gcc/testsuite/gcc.dg/strict-flex-array-3.c
>>>> new file mode 100644
>>>> index 00000000000..990c5bb6223
>>>> --- /dev/null
>>>> +++ b/gcc/testsuite/gcc.dg/strict-flex-array-3.c
>>>> @@ -0,0 +1,60 @@
>>>> +/* test the combination of attribute strict_flex_array and option
>>>> +   -fstrict-flex-array: when both attribute and option specified,
>>>> +   attribute will have higher priority.  */
>>>> +/* { dg-do run } */
>>>> +/* { dg-options "-O2 -fstrict-flex-array=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_array (1)));
>>>> +};
>>>> +
>>>> +struct trailing_array_2 {
>>>> +    int a;
>>>> +    int b;
>>>> +    int c[1] __attribute__ ((strict_flex_array (2)));
>>>> +};
>>>> +
>>>> +struct trailing_array_3 {
>>>> +    int a;
>>>> +    int b;
>>>> +    int c[0] __attribute__ ((strict_flex_array (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 4eb454a4a33..90710ecba72 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.  */
>>>> +	      bool is_flexible_array_mem_ref = false;
>>>> +	      /* For &X->fld, compute object size if fld isn't a flexible array
>>>> +		 member.  */
>>>> 	      while (v && v != pt_var)
>>>> 		switch (TREE_CODE (v))
>>>> 		  {
>>>> @@ -633,6 +633,9 @@ 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)
>>>> +			&& !DECL_NOT_FLEXARRAY (TREE_OPERAND (v, 1));
>>> 
>>> As said in the review for the first patch array_at_struct_end_p should
>>> check DECL_NOT_FLEXARRAY.
>> Okay.
>> 
>> Then, should we change the name of “array_at_struct_end_p” to a more 
>> descriptive name, for example,”flexible_array_member_p”? Otherwise, It’s 
>> really confusing.
> 
> It has been that way since forever, so please don't (at least not as
> part of this series).

Okay, I will keep the name as it in this set of patches.
(However, I do think that we should change the name of this routine, it’s really confusing…)

Qing
> 
>> 
>> 
>>> 
>>> OK with removing the extra check here.
>> 
>> Okay.
>> 
>> 
>> thanks.
>> 
>> Qing
>>> 
>>>> 		    while (v != pt_var && TREE_CODE (v) == COMPONENT_REF)
>>>> 		      if (TREE_CODE (TREE_TYPE (TREE_OPERAND (v, 0)))
>>>> 			  != UNION_TYPE
>>>> @@ -645,12 +648,9 @@ 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 <rguenther@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)
>> 
>> 
> 
> -- 
> Richard Biener <rguenther@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)
  

On Tue, Jul 19, 2022 at 02:11:19PM +0000, Qing Zhao wrote:
> From a09f39ded462611286a44d9e8273de8342673ba2 Mon Sep 17 00:00:00 2001
> From: Qing Zhao <qing.zhao@oracle.com>
> Date: Mon, 18 Jul 2022 18:12:26 +0000
> Subject: [PATCH 2/2] Use new flag DECL_NOT_FLEXARRAY in __builtin_object_size
> [PR101836]
> 
> Use new flag DECL_NOT_FLEXARRAY to determine whether the trailing array
> of a structure is flexible array member in __builtin_object_size.

FWIW, with these patches I've done builds of the Linux kernel using
the ...=3 level, and things are looking correct on our end. (There are,
as expected, many places in Linux that need to be fixed, and that work
is on-going, guided by this option's results.)

-Kees
  

Thanks a lot for your testing on Linux Kernel.
Will work on the version 3 of this patch soon.

Qing

> On Aug 2, 2022, at 11:30 AM, Kees Cook <keescook@chromium.org> wrote:
> 
> On Tue, Jul 19, 2022 at 02:11:19PM +0000, Qing Zhao wrote:
>> From a09f39ded462611286a44d9e8273de8342673ba2 Mon Sep 17 00:00:00 2001
>> From: Qing Zhao <qing.zhao@oracle.com>
>> Date: Mon, 18 Jul 2022 18:12:26 +0000
>> Subject: [PATCH 2/2] Use new flag DECL_NOT_FLEXARRAY in __builtin_object_size
>> [PR101836]
>> 
>> Use new flag DECL_NOT_FLEXARRAY to determine whether the trailing array
>> of a structure is flexible array member in __builtin_object_size.
> 
> FWIW, with these patches I've done builds of the Linux kernel using
> the ...=3 level, and things are looking correct on our end. (There are,
> as expected, many places in Linux that need to be fixed, and that work
> is on-going, guided by this option's results.)
> 
> -Kees
> 
> -- 
> Kees Cook