3 files changed, 37 insertions, 12 deletions
diff --git a/absl/strings/BUILD.bazel b/absl/strings/BUILD.bazel
index 49f49abd8d78..71d1606bd755 100644
--- a/absl/strings/BUILD.bazel
+++ b/absl/strings/BUILD.bazel
@@ -82,6 +82,7 @@ cc_library(
 cc_library(
     name = "internal",
     srcs = [
+        "internal/ostringstream.cc",
         "internal/utf8.cc",
     ],
     hdrs = [
diff --git a/absl/strings/internal/ostringstream.cc b/absl/strings/internal/ostringstream.cc
new file mode 100644
index 000000000000..6ee2b1090887
--- /dev/null
+++ b/absl/strings/internal/ostringstream.cc
@@ -0,0 +1,34 @@
+// Copyright 2017 The Abseil Authors.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include "absl/strings/internal/ostringstream.h"
+
+namespace absl {
+namespace strings_internal {
+
+OStringStream::Buf::int_type OStringStream::overflow(int c) {
+  assert(s_);
+  if (!Buf::traits_type::eq_int_type(c, Buf::traits_type::eof()))
+    s_->push_back(static_cast<char>(c));
+  return 1;
+}
+
+std::streamsize OStringStream::xsputn(const char* s, std::streamsize n) {
+  assert(s_);
+  s_->append(s, n);
+  return n;
+}
+
+}  // namespace strings_internal
+}  // namespace absl
diff --git a/absl/strings/internal/ostringstream.h b/absl/strings/internal/ostringstream.h
index 013146599d3d..6e1325b9140f 100644
--- a/absl/strings/internal/ostringstream.h
+++ b/absl/strings/internal/ostringstream.h
@@ -75,18 +75,8 @@ class OStringStream : private std::basic_streambuf<char>, public std::ostream {
  private:
   using Buf = std::basic_streambuf<char>;
 
-  Buf::int_type overflow(int c) override {
-    assert(s_);
-    if (!Buf::traits_type::eq_int_type(c, Buf::traits_type::eof()))
-      s_->push_back(static_cast<char>(c));
-    return 1;
-  }
-
-  std::streamsize xsputn(const char* s, std::streamsize n) override {
-    assert(s_);
-    s_->append(s, n);
-    return n;
-  }
+  Buf::int_type overflow(int c) override;
+  std::streamsize xsputn(const char* s, std::streamsize n) override;
 
   std::string* s_;
 };