Propagate GN public shared libraries through shared libraries

tools/gn/inherited_libraries.h

+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#ifndef TOOLS_GN_INHERITED_LIBRARIES_H_
+#define TOOLS_GN_INHERITED_LIBRARIES_H_
+
+#include <map>
+#include <utility>
+#include <vector>
+
+#include "base/basictypes.h"
+
+class Target;
+
+// Represents an ordered uniquified set of all shared/static libraries for
+// a given target. These are pushed up the dependency tree.

[Dirk Pranke, 2015/04/15 19:31:38]

why is ordered important?

+//
+// Since this list is uniquified, appending to the list will not actually
+// append a new item if the target already exists. However, the existing one
+// may have its is_public flag updated. "Public" always wins, so is_public will
+// be true if any dependency with that name has been set to public.
+class InheritedLibraries {
+ public:
+  InheritedLibraries();
+  ~InheritedLibraries();
+
+  // Returns the list of dependencies in order, optionally with the flag
+  // indicating whether the dependency is public.
+  std::vector<const Target*> GetOrdered() const;
+  std::vector<std::pair<const Target*, bool>> GetOrderedAndPublicFlag() const;
+
+  // Adds a single dependency to the end of the list. See note on adding above.
+  void Append(const Target* target, bool is_public);
+
+  // Appends all items from the "other" list to the current one. The is_public
+  // parameter indicates how the current target depends on the items in
+  // "other". If is_public is true, the existing public flags of the appended
+  // items will be preserved (propogating the public-ness up the dependency
+  // chain). If is_public is false, all deps will be added as private since
+  // the current target isn't forwarding them.
+  void AppendInherited(const InheritedLibraries& other, bool is_public);
+
+  // Like AppendInherited but only appends the items in "other" that are of
+  // type SHARED_LIBRARY and only when they're marked public. This is used
+  // to push shared libraries up the dependency chain, following only public
+  // deps, to dependent targets that need to use them.
+  void AppendPublicSharedLibraries(const InheritedLibraries& other,
+                                   bool is_public);
+
+ private:
+  struct Node {
+    Node() : index(static_cast<size_t>(-1)), is_public(false) {}
+    Node(size_t i, bool p) : index(i), is_public(p) {}
+
+    size_t index;
+    bool is_public;
+  };
+
+  typedef std::map<const Target*, Node> LibraryMap;
+  LibraryMap map_;
+
+  DISALLOW_COPY_AND_ASSIGN(InheritedLibraries);
+};
+
+#endif  // TOOLS_GN_INHERITED_LIBRARIES_H_