gdb

PR python/13281:
	* gdbtypes.h (TYPE_FLAG_ENUM): New macro.
	(struct main_type) <flag_flag_enum>: New field.
	* dwarf2read.c (process_enumeration_scope): Detect "flag" enums.
	* NEWS: Add entries.
	* c-valprint.c (c_val_print) <TYPE_CODE_ENUM>: Handle "flag"
	enums.
	* python/lib/gdb/printing.py (_EnumInstance): New class.
	(FlagEnumerationPrinter): Likewise.
gdb/doc
	* gdb.texinfo (gdb.printing): Document FlagEnumerationPrinter.
gdb/testsuite
	* gdb.base/printcmds.c (enum flag_enum): New.
	(three): New global.
	* gdb.base/printcmds.exp (test_print_enums): Add test for flag
	enum printing.
	* gdb.python/py-pp-maint.py (build_pretty_printer): Instantiate
	FlagEnumerationPrinter.
	* gdb.python/py-pp-maint.exp: Add tests for FlagEnumerationPrinter.
	* gdb.python/py-pp-maint.c (enum flag_enum): New.
	(fval): New global.

gdb/c-valprint.c

@@ -456,10 +456,41 @@ c_val_print (struct type *type, const gdb_byte *valaddr,
 	{
 	  fputs_filtered (TYPE_FIELD_NAME (type, i), stream);
 	}
-      else
+      else if (TYPE_FLAG_ENUM (type))
 	{
-	  print_longest (stream, 'd', 0, val);
+	  int first = 1;
+
+	  /* We have a "flag" enum, so we try to decompose it into
+	     pieces as appropriate.  A flag enum has disjoint
+	     constants by definition.  */
+	  fputs_filtered ("(", stream);
+	  for (i = 0; i < len; ++i)
+	    {
+	      QUIT;
+
+	      if ((val & TYPE_FIELD_BITPOS (type, i)) != 0)
+		{
+		  if (!first)
+		    fputs_filtered (" | ", stream);
+		  first = 0;
+
+		  val &= ~TYPE_FIELD_BITPOS (type, i);
+		  fputs_filtered (TYPE_FIELD_NAME (type, i), stream);
+		}
+	    }
+
+	  if (first || val != 0)
+	    {
+	      if (!first)
+		fputs_filtered (" | ", stream);
+	      fputs_filtered ("unknown: ", stream);
+	      print_longest (stream, 'd', 0, val);
+	    }
+
+	  fputs_filtered (")", stream);
 	}
+      else
+	print_longest (stream, 'd', 0, val);
       break;
 
     case TYPE_CODE_FLAGS: