Index: gcc/dwarf2out.c
===================================================================
--- gcc/dwarf2out.c	(revision 192405)
+++ gcc/dwarf2out.c	(working copy)
@@ -21218,6 +21218,7 @@
 prune_unused_types_prune (dw_die_ref die)
 {
   dw_die_ref c;
+  int pruned = 0;
 
   gcc_assert (die->die_mark);
   prune_unused_types_update_strings (die);
@@ -21240,13 +21241,24 @@
 	      prev->die_sib = c->die_sib;
 	      die->die_child = prev;
 	    }
-	  return;
+	  pruned = 1;
+	  goto finished;
 	}
 
     if (c != prev->die_sib)
-      prev->die_sib = c;
+      {
+	prev->die_sib = c;
+	pruned = 1;
+      }
     prune_unused_types_prune (c);
   } while (c != die->die_child);
+
+ finished:
+  /* If we pruned children, and this is a class, mark it as a 
+     declaration to inform debuggers that this is not a complete
+     class definition.  */
+  if (pruned && die->die_mark == 1 && class_scope_p (die))
+    add_AT_flag (die, DW_AT_declaration, 1);
 }
 
 /* Remove dies representing declarations that we never use.  */

Index: gcc/testsuite/g++.dg/debug/dwarf2/pr54508.C
===================================================================
--- gcc/testsuite/g++.dg/debug/dwarf2/pr54508.C	(revision 0)
+++ gcc/testsuite/g++.dg/debug/dwarf2/pr54508.C	(revision 0)
@@ -0,0 +1,72 @@
+// PR debug/54508
+// { dg-do compile }
+// { dg-options "-g2 -dA -fno-merge-debug-strings" }
+
+// { dg-final { scan-assembler-not "\"cbase\\\\0\"\[ \t\]+\[#;/!|@\]+ DW_AT_name" } }
+// { dg-final { scan-assembler "\"c\\\\0\"\[ \t\]+\[#;/!|@\]+ DW_AT_name\[\r\n\]+\[\^\r\n\]+\[\r\n\]+\[\^\r\n\]+\[\r\n\]+\[\^#;/!|@\]+\[#;/!|@\]+ DW_AT_decl_line\[\r\n\]+\[\^#;/!|@\]+\[#;/!|@\]+ DW_AT_declaration" } }
+// { dg-final { scan-assembler-not "\"OPCODE\\\\0\"\[ \t\]+\[#;/!|@\]+ DW_AT_name" } }
+// { dg-final { scan-assembler-not "\"bi\\\\0\"\[ \t\]+\[#;/!|@\]+ DW_AT_name" } }
+// { dg-final { scan-assembler-not "\"si\\\\0\"\[ \t\]+\[#;/!|@\]+ DW_AT_name" } }
+// { dg-final { scan-assembler "\"s\\\\0\"\[ \t\]+\[#;/!|@\]+ DW_AT_name" } }
+// { dg-final { scan-assembler-not "\"s\\\\0\"\[^#;/!|@\]+\[#;/!|@\]+ DW_AT_name\[\r\n\]+\[\^\r\n\]+\[\r\n\]+\[\^\r\n\]+\[\r\n\]+\[\^#;/!|@\]+\[#;/!|@\]+ DW_AT_decl_line\[\r\n\]+\[ \t\]+\[#;/!|@\]+ DW_AT_declaration" } }
+// { dg-final { scan-assembler "\"f1\\\\0\"\[ \t\]+\[#;/!|@\]+ DW_AT_name" } }
+// { dg-final { scan-assembler "\"u\\\\0\"\[ \t\]+\[#;/!|@\]+ DW_AT_name\[\r\n\]+\[\^\r\n\]+\[\r\n\]+\[\^\r\n\]+\[\r\n\]+\[\^#;/!|@\]+\[#;/!|@\]+ DW_AT_decl_line\[\r\n\]+\[^#;/!|@\]+\[#;/!|@\]+ DW_AT_declaration" } }
+// { dg-final { scan-assembler-not "\"f2\\\\0\"\[ \t\]+\[#;/!|@\]+ DW_AT_name" } }
+// { dg-final { scan-assembler-not "\"nc\\\\0\"\[ \t\]+\# DW_AT_name" } }
+
+class cbase
+
+{
+public:
+ static int si;
+    int bi;
+};
+
+class c : public cbase
+
+{
+public:
+ enum
+ {
+  OPCODE = 251
+ };
+ int i ;
+ static const char *testc (void) { return "foo"; }
+};
+
+struct s
+{
+    int f1;
+    static const char *tests (void) { return "test"; }
+};
+
+union u
+{
+    int f2;
+    double d;
+    static const char *testu (void) { return "test union"; }
+};
+
+namespace n 
+{
+    const char *ntest (void) { return "test n"; }
+
+    class nc
+    {
+    public:
+        int i;
+        static int sj;
+    };
+}
+
+extern void send (int, int, const void *, int);
+
+void test (int src)
+{
+  int cookie = 1;
+  static struct s ss;
+  
+  send(src, c::OPCODE, c::testc (), cookie);
+  send(src, c::OPCODE, u::testu (), cookie);
+  send(src, c::OPCODE, n::ntest (), cookie);
+}