Fix glog/stl_logging for clang

git-svn-id: https://google-glog.googlecode.com/svn/trunk@118 eb4d4688-79bd-11dd-afb4-1d65580434c0

src/glog/stl_logging.h.in

@@ -34,27 +34,6 @@
 // LOG(INFO) << "data: " << x;
 // vector<int> v1, v2;
 // CHECK_EQ(v1, v2);
-//
-// Note that if you want to use these operators from the non-global namespace,
-// you may get an error since they are not in namespace std (and they are not
-// in namespace std since that would result in undefined behavior). You may
-// need to write
-//
-//   using ::operator<<;
-//
-// to fix these errors.
-//
-//
-// Notice for clang users: you should include stl_logging.h BEFORE you
-// include logging.h. Otherwise, you will see some errors when you use
-// CHECK with STL containers.
-//
-// Clang's "using ::operator<<" incorporate symbols which are declared
-// before the using keyword. With GCC, symbols defined after the using
-// keyword are incorporated as well. The CHECK macro defined in
-// logging.h uses the using keyword so you need to include logging.h
-// after including stl_logging.h.
-//
 
 #ifndef UTIL_GTL_STL_LOGGING_INL_H_
 #define UTIL_GTL_STL_LOGGING_INL_H_
@@ -77,27 +56,16 @@
 # include <ext/slist>
 #endif
 
+// Forward declare these two, and define them after all the container streams
+// operators so that we can recurse from pair -> container -> container -> pair
+// properly.
 template<class First, class Second>
-inline std::ostream& operator<<(std::ostream& out,
+std::ostream& operator<<(std::ostream& out, const std::pair<First, Second>& p);
-                                const std::pair<First, Second>& p) {
-  out << '(' << p.first << ", " << p.second << ')';
-  return out;
-}
 
 @ac_google_start_namespace@
 
 template<class Iter>
-inline void PrintSequence(std::ostream& out, Iter begin, Iter end) {
+void PrintSequence(std::ostream& out, Iter begin, Iter end);
-  using ::operator<<;
-  // Output at most 100 elements -- appropriate if used for logging.
-  for (int i = 0; begin != end && i < 100; ++i, ++begin) {
-    if (i > 0) out << ' ';
-    out << *begin;
-  }
-  if (begin != end) {
-    out << " ...";
-  }
-}
 
 @ac_google_end_namespace@
 
@@ -163,4 +131,53 @@ OUTPUT_FIVE_ARG_CONTAINER(__gnu_cxx::hash_multimap)
 
 #undef OUTPUT_FIVE_ARG_CONTAINER
 
+template<class First, class Second>
+inline std::ostream& operator<<(std::ostream& out,
+                                const std::pair<First, Second>& p) {
+  out << '(' << p.first << ", " << p.second << ')';
+  return out;
+}
+
+@ac_google_start_namespace@
+
+template<class Iter>
+inline void PrintSequence(std::ostream& out, Iter begin, Iter end) {
+  // Output at most 100 elements -- appropriate if used for logging.
+  for (int i = 0; begin != end && i < 100; ++i, ++begin) {
+    if (i > 0) out << ' ';
+    out << *begin;
+  }
+  if (begin != end) {
+    out << " ...";
+  }
+}
+
+@ac_google_end_namespace@
+
+// Note that this is technically undefined behavior! We are adding things into
+// the std namespace for a reason though -- we are providing new operations on
+// types which are themselves defined with this namespace. Without this, these
+// operator overloads cannot be found via ADL. If these definitions are not
+// found via ADL, they must be #included before they're used, which requires
+// this header to be included before apparently independent other headers.
+//
+// For example, base/logging.h defines various template functions to implement
+// CHECK_EQ(x, y) and stream x and y into the log in the event the check fails.
+// It does so via the function template MakeCheckOpValueString:
+//   template<class T>
+//   void MakeCheckOpValueString(strstream* ss, const T& v) {
+//     (*ss) << v;
+//   }
+// Because 'glog/logging.h' is included before 'glog/stl_logging.h',
+// subsequent CHECK_EQ(v1, v2) for vector<...> typed variable v1 and v2 can only
+// find these operator definitions via ADL.
+//
+// Even this solution has problems -- it may pull unintended operators into the
+// namespace as well, allowing them to also be found via ADL, and creating code
+// that only works with a particular order of includes. Long term, we need to
+// move all of the *definitions* into namespace std, bet we need to ensure no
+// one references them first. This lets us take that step. We cannot define them
+// in both because that would create ambiguous overloads when both are found.
+namespace std { using ::operator<<; }
+
 #endif  // UTIL_GTL_STL_LOGGING_INL_H_

src/windows/glog/stl_logging.h

@@ -38,27 +38,6 @@
 // LOG(INFO) << "data: " << x;
 // vector<int> v1, v2;
 // CHECK_EQ(v1, v2);
-//
-// Note that if you want to use these operators from the non-global namespace,
-// you may get an error since they are not in namespace std (and they are not
-// in namespace std since that would result in undefined behavior). You may
-// need to write
-//
-//   using ::operator<<;
-//
-// to fix these errors.
-//
-//
-// Notice for clang users: you should include stl_logging.h BEFORE you
-// include logging.h. Otherwise, you will see some errors when you use
-// CHECK with STL containers.
-//
-// Clang's "using ::operator<<" incorporate symbols which are declared
-// before the using keyword. With GCC, symbols defined after the using
-// keyword are incorporated as well. The CHECK macro defined in
-// logging.h uses the using keyword so you need to include logging.h
-// after including stl_logging.h.
-//
 
 #ifndef UTIL_GTL_STL_LOGGING_INL_H_
 #define UTIL_GTL_STL_LOGGING_INL_H_
@@ -81,27 +60,16 @@
 # include <ext/slist>
 #endif
 
+// Forward declare these two, and define them after all the container streams
+// operators so that we can recurse from pair -> container -> container -> pair
+// properly.
 template<class First, class Second>
-inline std::ostream& operator<<(std::ostream& out,
+std::ostream& operator<<(std::ostream& out, const std::pair<First, Second>& p);
-                                const std::pair<First, Second>& p) {
-  out << '(' << p.first << ", " << p.second << ')';
-  return out;
-}
 
 namespace google {
 
 template<class Iter>
-inline void PrintSequence(std::ostream& out, Iter begin, Iter end) {
+void PrintSequence(std::ostream& out, Iter begin, Iter end);
-  using ::operator<<;
-  // Output at most 100 elements -- appropriate if used for logging.
-  for (int i = 0; begin != end && i < 100; ++i, ++begin) {
-    if (i > 0) out << ' ';
-    out << *begin;
-  }
-  if (begin != end) {
-    out << " ...";
-  }
-}
 
 }
 
@@ -167,4 +135,53 @@ OUTPUT_FIVE_ARG_CONTAINER(__gnu_cxx::hash_multimap)
 
 #undef OUTPUT_FIVE_ARG_CONTAINER
 
+template<class First, class Second>
+inline std::ostream& operator<<(std::ostream& out,
+                                const std::pair<First, Second>& p) {
+  out << '(' << p.first << ", " << p.second << ')';
+  return out;
+}
+
+namespace google {
+
+template<class Iter>
+inline void PrintSequence(std::ostream& out, Iter begin, Iter end) {
+  // Output at most 100 elements -- appropriate if used for logging.
+  for (int i = 0; begin != end && i < 100; ++i, ++begin) {
+    if (i > 0) out << ' ';
+    out << *begin;
+  }
+  if (begin != end) {
+    out << " ...";
+  }
+}
+
+}
+
+// Note that this is technically undefined behavior! We are adding things into
+// the std namespace for a reason though -- we are providing new operations on
+// types which are themselves defined with this namespace. Without this, these
+// operator overloads cannot be found via ADL. If these definitions are not
+// found via ADL, they must be #included before they're used, which requires
+// this header to be included before apparently independent other headers.
+//
+// For example, base/logging.h defines various template functions to implement
+// CHECK_EQ(x, y) and stream x and y into the log in the event the check fails.
+// It does so via the function template MakeCheckOpValueString:
+//   template<class T>
+//   void MakeCheckOpValueString(strstream* ss, const T& v) {
+//     (*ss) << v;
+//   }
+// Because 'glog/logging.h' is included before 'glog/stl_logging.h',
+// subsequent CHECK_EQ(v1, v2) for vector<...> typed variable v1 and v2 can only
+// find these operator definitions via ADL.
+//
+// Even this solution has problems -- it may pull unintended operators into the
+// namespace as well, allowing them to also be found via ADL, and creating code
+// that only works with a particular order of includes. Long term, we need to
+// move all of the *definitions* into namespace std, bet we need to ensure no
+// one references them first. This lets us take that step. We cannot define them
+// in both because that would create ambiguous overloads when both are found.
+namespace std { using ::operator<<; }
+
 #endif  // UTIL_GTL_STL_LOGGING_INL_H_