Fix PR c++/23373: GDB hangs when printing a struct with a static member of itself

This patch fixes a failure that happens when a structure has a static
member whose type is the same as itself.  From the bug report:

  Example code:
  struct A
  {
      static A Empty;
      int a;
  };

  int main(void) {
      A a;
      return 0;
  }

  Output:
  (gdb) ptype/o A
  /* offset    |  size */  type = struct A {
			     static struct A {
				 static struct A {
				     static struct A {
					 static struct A {
					     static struct A {
						 static struct A {
						     ... # infinite loop

The problem here is that GDB is not taking into account the fact that
static members inside a class/struct are not stored in the
class/struct, and therefore they should not be accounted for during
the display of the offsets/sizes.  The fix is simple: we just check if
the field we're dealing with (on
c-typeprint.c:c_type_print_base_struct_union) is static, and if it is
then we don't iterate over it.

This patch also adds a new test for this case, and doesn't introduce
any regressions.  I believe it is important enough to be included in
the 8.2 branch.

OK?

gdb/ChangeLog:
2018-07-11  Sergio Durigan Junior  <sergiodj@redhat.com>

	PR c++/23373
	* c-typeprint.c (c_type_print_base_struct_union): Don't print
	offsets/sizes for static members of a class/struct.

gdb/testsuite/ChangeLog:
2018-07-11  Sergio Durigan Junior  <sergiodj@redhat.com>

	PR c++/23373
	* gdb.base/ptype-offsets.cc (struct static_member): New
	struct.
	(main) <stmember>: New variable.
	* gdb.base/ptype-offsets.exp: Add test for printing a struct
	with a static member in it.

Author: Sergio Durigan Junior

gdb/ChangeLog

@@ -1,3 +1,9 @@
+2018-07-11  Sergio Durigan Junior  <sergiodj@redhat.com>
+
+	PR c++/23373
+	* c-typeprint.c (c_type_print_base_struct_union): Don't print
+	offsets/sizes for static members of a class/struct.
+
 2018-07-07  Jan Kratochvil  <jan.kratochvil@redhat.com>
 
 	* contrib/gdb-add-index.sh ($dwarf5): New, use it.

gdb/c-typeprint.c

@@ -1168,7 +1168,7 @@ c_type_print_base_struct_union (struct type *type, struct ui_file *stream,
 
 	  int newshow = show - 1;
 
-	  if (flags->print_offsets
+	  if (!is_static && flags->print_offsets
 	      && (TYPE_CODE (TYPE_FIELD_TYPE (type, i)) == TYPE_CODE_STRUCT
 		  || TYPE_CODE (TYPE_FIELD_TYPE (type, i)) == TYPE_CODE_UNION))
 	    {

gdb/testsuite/ChangeLog

@@ -1,3 +1,12 @@
+2018-07-11  Sergio Durigan Junior  <sergiodj@redhat.com>
+
+	PR c++/23373
+	* gdb.base/ptype-offsets.cc (struct static_member): New
+	struct.
+	(main) <stmember>: New variable.
+	* gdb.base/ptype-offsets.exp: Add test for printing a struct
+	with a static member in it.
+
 2018-07-04  Tom de Vries  <tdevries@suse.de>
 
 	* gdb.dwarf2/dw2-error.exp: Update expected error message.

gdb/testsuite/gdb.base/ptype-offsets.cc

@@ -177,6 +177,13 @@ struct asd
   void *f16;
 };
 
+/* See PR c++/23373.  */
+
+struct static_member
+{
+  static static_member Empty;
+  int abc;
+};
 
 int
 main (int argc, char *argv[])
@@ -188,6 +195,7 @@ main (int argc, char *argv[])
   struct tyu e;
   struct asd f;
   uint8_t i;
+  static_member stmember;
 
   return 0;
 }

gdb/testsuite/gdb.base/ptype-offsets.exp

@@ -328,3 +328,14 @@ gdb_test_multiple "$test" "$test" {
        pass $test
    }
 }
+
+# Test that printing a struct with a static member of itself doesn't
+# get us into an infinite loop.
+gdb_test "ptype/o static_member" \
+    [multi_line \
+{/\* offset    |  size \*/  type = struct static_member \{} \
+{                           static static_member Empty;} \
+{\/*    0      |     4 \*/    int abc;} \
+{} \
+{                           /\* total size \(bytes\):    4 \*/} \
+{                         \}}]