Use array_at_struct_end_p in __builtin_object_size [PR101836]

Use array_at_struct_end_p 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
	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.

1 files changed, 60 insertions, 0 deletions

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 0000000..602f99d
--- /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-arrays: when both attribute and option specified,
+   attribute will have higher priority.  */
+/* { dg-do run } */
+/* { dg-options "-O2 -fstrict-flex-arrays=0" } */
+
+#include <stdio.h>
+
+#define expect(p, _v) do { \
+    size_t v = _v; \
+    if (p == v) \
+        printf("ok:  %s == %zd\n", #p, p); \
+    else \
+	{  \
+          printf("WAT: %s == %zd (expected %zd)\n", #p, p, v); \
+	  __builtin_abort (); \
+	} \
+} while (0);
+
+struct trailing_array_1 {
+    int a;
+    int b;
+    int c[4] __attribute__ ((strict_flex_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;
+}