Introduce a separate debug objfile iterator

This introduces a new iterator and range adapter for iteration over
the separate debug files of a given objfile.  As in the current
approach, the requested objfile is returned first, followed by the
separate debug objfiles.

gdb/ChangeLog
2019-04-10  Tom Tromey  <tom@tromey.com>

	* symtab.c (lookup_global_symbol_from_objfile)
	(lookup_symbol_in_objfile_from_linkage_name): Use the iterator.
	* objfiles.h (class separate_debug_iterator): New.
	(class separate_debug_range): New.
	(struct objfile) <separate_debug_objfiles>: New method.
	(objfile_separate_debug_iterate): Don't declare.
	* objfiles.c (separate_debug_iterator::operator++): Rename from
	objfile_separate_debug_iterate.
	(objfile_relocate, objfile_rebase, objfile_has_symbols): Use the
	iterator.
	* minsyms.c (lookup_minimal_symbol_by_pc_section): Use the
	iterator.

gdb/objfiles.h

@@ -318,6 +318,63 @@ struct objfile_per_bfd_storage
   std::bitset<nr_languages> demangled_hash_languages;
 };
 
+/* An iterator that first returns a parent objfile, and then each
+   separate debug objfile.  */
+
+class separate_debug_iterator
+{
+public:
+
+  explicit separate_debug_iterator (struct objfile *objfile)
+    : m_objfile (objfile),
+      m_parent (objfile)
+  {
+  }
+
+  bool operator!= (const separate_debug_iterator &other)
+  {
+    return m_objfile != other.m_objfile;
+  }
+
+  separate_debug_iterator &operator++ ();
+
+  struct objfile *operator* ()
+  {
+    return m_objfile;
+  }
+
+private:
+
+  struct objfile *m_objfile;
+  struct objfile *m_parent;
+};
+
+/* A range adapter wrapping separate_debug_iterator.  */
+
+class separate_debug_range
+{
+public:
+
+  explicit separate_debug_range (struct objfile *objfile)
+    : m_objfile (objfile)
+  {
+  }
+
+  separate_debug_iterator begin ()
+  {
+    return separate_debug_iterator (m_objfile);
+  }
+
+  separate_debug_iterator end ()
+  {
+    return separate_debug_iterator (nullptr);
+  }
+
+private:
+
+  struct objfile *m_objfile;
+};
+
 /* Master structure for keeping track of each file from which
    gdb reads symbols.  There are several ways these get allocated: 1.
    The main symbol file, symfile_objfile, set by the symbol-file command,
@@ -396,6 +453,14 @@ struct objfile
     return msymbols_range (this);
   }
 
+  /* Return a range adapter for iterating over all the separate debug
+     objfiles of this objfile.  */
+
+  separate_debug_range separate_debug_objfiles ()
+  {
+    return separate_debug_range (this);
+  }
+
 
   /* All struct objfile's are chained together by their next pointers.
      The program space field "objfiles"  (frequently referenced via
@@ -563,9 +628,6 @@ extern CORE_ADDR entry_point_address (void);
 
 extern void build_objfile_section_table (struct objfile *);
 
-extern struct objfile *objfile_separate_debug_iterate (const struct objfile *,
-                                                       const struct objfile *);
-
 extern void put_objfile_before (struct objfile *, struct objfile *);
 
 extern void add_separate_debug_objfile (struct objfile *, struct objfile *);