Add testing cases for flexible array members in unions and alone in structures.

PR c/53548

gcc/testsuite/ChangeLog:

	PR c/53548
	* c-c++-common/fam-in-union-alone-in-struct-1.c: New testcase.
	* c-c++-common/fam-in-union-alone-in-struct-2.c: New testcase.
	* c-c++-common/fam-in-union-alone-in-struct-3.c: New testcase.

3 files changed, 139 insertions, 0 deletions

diff --git a/gcc/testsuite/c-c++-common/fam-in-union-alone-in-struct-1.c b/gcc/testsuite/c-c++-common/fam-in-union-alone-in-struct-1.c
new file mode 100644
index 0000000..7d4721a
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fam-in-union-alone-in-struct-1.c
@@ -0,0 +1,52 @@
+/* testing the correct usage of flexible array members in unions 
+   and alone in structures.  */
+/* { dg-do run} */
+/* { dg-options "-Wpedantic" } */
+
+union with_fam_1 {
+  int a;
+  int b[];  /* { dg-warning "flexible array member in union is a GCC extension" } */
+};
+
+union with_fam_2 {
+  char a;
+  int b[];  /* { dg-warning "flexible array member in union is a GCC extension" } */
+};
+
+union with_fam_3 {
+  char a[];  /* { dg-warning "flexible array member in union is a GCC extension" } */
+  /* { dg-warning "in an otherwise empty" "" { target c++ } .-1 } */
+  int b[];  /* { dg-warning "flexible array member in union is a GCC extension" } */
+};
+
+struct only_fam {
+  int b[];
+  /* { dg-warning "in a struct with no named members" "" { target c } .-1 } */
+  /* { dg-warning "in an otherwise empty" "" { target c++ } .-2 } */
+  /* { dg-warning "forbids flexible array member" "" { target c++ } .-3 } */
+};
+
+struct only_fam_2 {
+  unsigned int : 2;
+  unsigned int : 3;
+  int b[];
+  /* { dg-warning "in a struct with no named members" "" { target c } .-1 } */
+  /* { dg-warning "in an otherwise empty" "" { target c++ } .-2 } */
+  /* { dg-warning "forbids flexible array member" "" { target c++ } .-3 } */
+};
+
+int main ()
+{
+  if (sizeof (union with_fam_1) != sizeof (int))
+    __builtin_abort ();
+  if (sizeof (union with_fam_2) != __alignof__ (int))
+    __builtin_abort ();
+  if (sizeof (union with_fam_3) != 0)
+    __builtin_abort ();
+  if (sizeof (struct only_fam) != 0)
+    __builtin_abort ();
+  if (sizeof (struct only_fam_2) != sizeof (int))
+    __builtin_abort ();
+  return 0;
+}
+
diff --git a/gcc/testsuite/c-c++-common/fam-in-union-alone-in-struct-2.c b/gcc/testsuite/c-c++-common/fam-in-union-alone-in-struct-2.c
new file mode 100644
index 0000000..3743f9e
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fam-in-union-alone-in-struct-2.c
@@ -0,0 +1,51 @@
+/* testing the correct usage of flexible array members in unions 
+   and alone in structures: initialization  */
+/* { dg-do run} */
+/* { dg-options "-O2" } */
+
+union with_fam_1 {
+  int a;
+  int b[]; 
+} with_fam_1_v = {.b = {1, 2, 3, 4}};
+
+union with_fam_2 {
+  int a;
+  char b[];  
+} with_fam_2_v = {.a = 0x1f2f3f4f};
+
+union with_fam_3 {
+  char a[];  
+  int b[];  
+} with_fam_3_v = {.b = {0x1f2f3f4f, 0x5f6f7f7f}};
+
+struct only_fam {
+  int b[]; 
+} only_fam_v = {{7, 11}};
+
+struct only_fam_2 {
+  unsigned int : 2;
+  unsigned int : 3;
+  int b[]; 
+} only_fam_2_v = {{7, 11}};
+
+int main ()
+{
+  if (with_fam_1_v.b[3] != 4
+      || with_fam_1_v.b[0] != 1)
+    __builtin_abort ();
+  if (with_fam_2_v.b[3] != 0x1f
+      || with_fam_2_v.b[0] != 0x4f)
+    __builtin_abort ();
+  if (with_fam_3_v.a[0] != 0x4f
+      || with_fam_3_v.a[7] != 0x5f)
+    __builtin_abort ();
+  if (only_fam_v.b[0] != 7
+      || only_fam_v.b[1] != 11)
+    __builtin_abort ();
+  if (only_fam_2_v.b[0] != 7
+      || only_fam_2_v.b[1] != 11)
+    __builtin_abort ();
+
+  return 0;
+}
+
diff --git a/gcc/testsuite/c-c++-common/fam-in-union-alone-in-struct-3.c b/gcc/testsuite/c-c++-common/fam-in-union-alone-in-struct-3.c
new file mode 100644
index 0000000..dd36fa0
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/fam-in-union-alone-in-struct-3.c
@@ -0,0 +1,36 @@
+/* testing the correct usage of flexible array members in unions 
+   and alone in structures.  */
+/* { dg-do compile } */
+/* { dg-options "-pedantic-errors" } */
+
+union with_fam_1 {
+  int a;
+  int b[];  /* { dg-error "flexible array member in union is a GCC extension" } */
+};
+
+union with_fam_2 {
+  char a;
+  int b[];  /* { dg-error "flexible array member in union is a GCC extension" } */
+};
+
+union with_fam_3 {
+  char a[];  /* { dg-error "flexible array member in union is a GCC extension" } */
+  /* { dg-error "in an otherwise empty" "" { target c++ } .-1 } */
+  int b[];  /* { dg-error "flexible array member in union is a GCC extension" } */
+};
+
+struct only_fam {
+  int b[];
+  /* { dg-error "in a struct with no named members" "" { target c } .-1 } */
+  /* { dg-error "in an otherwise empty" "" { target c++ } .-2 } */
+  /* { dg-error "forbids flexible array member" "" { target c++ } .-3 } */
+};
+
+struct only_fam_2 {
+  unsigned int : 2;
+  unsigned int : 3;
+  int b[];
+  /* { dg-error "in a struct with no named members" "" { target c } .-1 } */
+  /* { dg-error "in an otherwise empty" "" { target c++ } .-2 } */
+  /* { dg-error "forbids flexible array member" "" { target c++ } .-3 } */
+};