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

[Qing Zhao <qing.zhao@oracle.com>]

> 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)