diff --git a/Android.mk b/Android.mk
index 5b844e4..b27a4df 100644
--- a/Android.mk
+++ b/Android.mk
@@ -99,6 +99,7 @@
     ast_cpp_unittest.cpp \
     ast_java_unittest.cpp \
     generate_cpp_unittest.cpp \
+    io_delegate_unittest.cpp \
     options_unittest.cpp \
     tests/end_to_end_tests.cpp \
     tests/fake_io_delegate.cpp \
diff --git a/aidl.cpp b/aidl.cpp
index 6f542bf..10a90e4 100644
--- a/aidl.cpp
+++ b/aidl.cpp
@@ -77,23 +77,10 @@
     string expected;
     string fn;
     size_t len;
-    char cwd[MAXPATHLEN];
     bool valid = false;
 
-#ifdef _WIN32
-    if (isalpha(filename[0]) && filename[1] == ':'
-        && filename[2] == OS_PATH_SEPARATOR) {
-#else
-    if (filename[0] == OS_PATH_SEPARATOR) {
-#endif
-        fn = filename;
-    } else {
-        fn = getcwd(cwd, sizeof(cwd));
-        len = fn.length();
-        if (fn[len-1] != OS_PATH_SEPARATOR) {
-            fn += OS_PATH_SEPARATOR;
-        }
-        fn += filename;
+    if (!IoDelegate::GetAbsolutePath(filename, &fn)) {
+      return false;
     }
 
     if (!package.empty()) {
diff --git a/io_delegate.cpp b/io_delegate.cpp
index 66891dd..62be3f5 100644
--- a/io_delegate.cpp
+++ b/io_delegate.cpp
@@ -41,6 +41,45 @@
 namespace android {
 namespace aidl {
 
+bool IoDelegate::GetAbsolutePath(const string& path, string* absolute_path) {
+#ifdef _WIN32
+
+  char buf[4096];
+  DWORD path_len = GetFullPathName(path.c_str(), sizeof(buf), buf, nullptr);
+  if (path_len <= 0 || path_len >= sizeof(buf)) {
+    LOG(ERROR) << "Failed to GetFullPathName(" << path << ")";
+    return false;
+  }
+  *absolute_path = buf;
+
+  return true;
+
+#else
+
+  if (path.empty()) {
+    LOG(ERROR) << "Giving up on finding an absolute path to represent the "
+                  "empty string.";
+    return false;
+  }
+  if (path[0] == OS_PATH_SEPARATOR) {
+    *absolute_path = path;
+    return true;
+  }
+
+  char buf[4096];
+  if (getcwd(buf, sizeof(buf)) == nullptr) {
+    LOG(ERROR) << "Path of current working directory does not fit in "
+               << sizeof(buf) << " bytes";
+    return false;
+  }
+
+  *absolute_path = buf;
+  *absolute_path += OS_PATH_SEPARATOR;
+  *absolute_path += path;
+  return true;
+#endif
+}
+
 unique_ptr<string> IoDelegate::GetFileContents(
     const string& filename,
     const string& content_suffix) const {
@@ -112,15 +151,26 @@
     return true;
   }
 
-  string base = ".";
-  if (path[0] == OS_PATH_SEPARATOR) {
-    base = "/";
+  string absolute_path;
+  if (!GetAbsolutePath(path, &absolute_path)) {
+    return false;
   }
 
-  auto split = Split(path, string{1u, OS_PATH_SEPARATOR});
-  split.pop_back();
+  auto directories = Split(absolute_path, string{1u, OS_PATH_SEPARATOR});
 
-  return CreatedNestedDirs(base, split);
+  // The "base" directory is just the root of the file system.  On Windows,
+  // this will look like "C:\" but on Unix style file systems we get an empty
+  // string after splitting "/foo" with "/"
+  string base = directories[0];
+  if (base.empty()) {
+    base = "/";
+  }
+  directories.erase(directories.begin());
+
+  // Remove the actual file in question, we're just creating the directory path.
+  directories.pop_back();
+
+  return CreatedNestedDirs(base, directories);
 }
 
 unique_ptr<CodeWriter> IoDelegate::GetCodeWriter(
diff --git a/io_delegate.h b/io_delegate.h
index b0a703b..dc9a3e3 100644
--- a/io_delegate.h
+++ b/io_delegate.h
@@ -34,6 +34,12 @@
   IoDelegate() = default;
   virtual ~IoDelegate() = default;
 
+  // Stores an absolute version of |path| to |*absolute_path|,
+  // possibly prefixing it with the current working directory.
+  // Returns false and does not set |*absolute_path| on error.
+  static bool GetAbsolutePath(const std::string& path,
+                              std::string* absolute_path);
+
   // Returns a unique_ptr to the contents of |filename|.
   // Will append the optional |content_suffix| to the returned contents.
   virtual std::unique_ptr<std::string> GetFileContents(
diff --git a/io_delegate_unittest.cpp b/io_delegate_unittest.cpp
new file mode 100644
index 0000000..5227d0b
--- /dev/null
+++ b/io_delegate_unittest.cpp
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2016, The Android Open Source Project
+ *
+ * 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 <string>
+
+#include <gtest/gtest.h>
+
+#include "io_delegate.h"
+
+using std::string;
+
+namespace android {
+namespace aidl {
+
+TEST(IoDelegateTest, CannotGetAbsolutePathFromEmptyString) {
+  string absolute_path;
+  EXPECT_FALSE(IoDelegate::GetAbsolutePath("", &absolute_path));
+  EXPECT_TRUE(absolute_path.empty());
+}
+
+TEST(IoDelegateTest, CurrentlyInfersLinuxAbsolutePath) {
+  string absolute_path;
+  EXPECT_TRUE(IoDelegate::GetAbsolutePath("foo", &absolute_path));
+  ASSERT_FALSE(absolute_path.empty());
+  // Should find our desired file at the end of |absolute_path|
+  // But we don't know the prefix, since it's the current working directory
+  EXPECT_TRUE(absolute_path.rfind("/foo") == absolute_path.length() - 4);
+  // Whatever our current working directory, the path is absolute.
+  EXPECT_EQ(absolute_path[0], '/');
+}
+
+}  // namespace android
+}  // namespace aidl