4 files changed, 39 insertions, 9 deletions
diff --git a/src/main/cpp/blaze.cc b/src/main/cpp/blaze.cc
index 0c4fa76a79..336dbc2d8e 100644
--- a/src/main/cpp/blaze.cc
+++ b/src/main/cpp/blaze.cc
@@ -1009,6 +1009,8 @@ static void EnsureCorrectRunningVersion() {
   // installation is running.
   string installation_path = globals->options.output_base + "/install";
   char prev_installation[PATH_MAX + 1] = "";  // NULs the whole array
+  // TODO(dslomov): On Windows, readlink always fails,
+  // so we do the linking every time.
   if (readlink(installation_path.c_str(),
                prev_installation, PATH_MAX) == -1 ||
       prev_installation != globals->options.install_base) {
@@ -1016,8 +1018,8 @@ static void EnsureCorrectRunningVersion() {
       globals->restart_reason = NEW_VERSION;
     }
     unlink(installation_path.c_str());
-    if (symlink(globals->options.install_base.c_str(),
-                installation_path.c_str())) {
+    if (!SymlinkDirectories(globals->options.install_base.c_str(),
+                            installation_path.c_str())) {
       pdie(blaze_exit_code::LOCAL_ENVIRONMENTAL_ERROR,
            "failed to create installation symlink '%s'",
            installation_path.c_str());
diff --git a/src/main/cpp/blaze_util_mingw.cc b/src/main/cpp/blaze_util_mingw.cc
index d3ebfedaa1..c959f00f6d 100644
--- a/src/main/cpp/blaze_util_mingw.cc
+++ b/src/main/cpp/blaze_util_mingw.cc
@@ -115,12 +115,11 @@ void ReplaceAll(
     pos += with.length();
   }
 }
-}  // namespace
 
-// Replace the current process with the given program in the given working
-// directory, using the given argument vector.
-// This function does not return on success.
-void ExecuteProgram(const string& exe, const vector<string>& args_vector) {
+// Run the given program in the current working directory,
+// using the given argument vector.
+DWORD CreateProcessWrapper(
+    const string& exe, const vector<string>& args_vector) {
   if (VerboseLogging()) {
     string dbg;
     for (const auto& s : args_vector) {
@@ -212,9 +211,16 @@ void ExecuteProgram(const string& exe, const vector<string>& args_vector) {
   GetExitCodeProcess(pi.hProcess, &exit_code);
   CloseHandle(pi.hProcess);
   CloseHandle(pi.hThread);
+  return exit_code;
+}
+}  // namespace
 
+// Replace the current process with the given program in the current working
+// directory, using the given argument vector.
+// This function does not return on success.
+void ExecuteProgram(const string& exe, const vector<string>& args_vector) {
   // Emulate execv.
-  exit(exit_code);
+  exit(CreateProcessWrapper(exe, args_vector));
 }
 
 string ListSeparator() { return ";"; }
@@ -227,4 +233,17 @@ string ConvertPath(const string& path) {
   return result;
 }
 
+bool SymlinkDirectories(const string &target, const string &link) {
+  const string target_win = ConvertPath(target);
+  const string link_win = ConvertPath(link);
+  vector<string> args;
+  args.push_back("cmd");
+  args.push_back("/C");
+  args.push_back("mklink");
+  args.push_back("/J");
+  args.push_back(link_win);
+  args.push_back(target_win);
+  return CreateProcessWrapper("cmd", args) == 0;
+}
+
 }  // namespace blaze
diff --git a/src/main/cpp/blaze_util_platform.h b/src/main/cpp/blaze_util_platform.h
index a3b315c484..4aa462ed0b 100644
--- a/src/main/cpp/blaze_util_platform.h
+++ b/src/main/cpp/blaze_util_platform.h
@@ -54,7 +54,7 @@ bool IsSharedLibrary(const std::string& filename);
 // (must be an absolute directory).
 std::string GetDefaultHostJavabase();
 
-// Replace the current process with the given program in the given working
+// Replace the current process with the given program in the current working
 // directory, using the given argument vector.
 // This function does not return on success.
 void ExecuteProgram(const string& exe, const std::vector<string>& args_vector);
@@ -68,6 +68,11 @@ std::string ConvertPath(const std::string& path);
 // Return a string used to separate paths in a list.
 std::string ListSeparator();
 
+// Create a symlink to directory ``target`` at location ``link``.
+// Returns true on success, false on failure.
+// Implemented via junctions on Windows.
+bool SymlinkDirectories(const string &target, const string &link);
+
 }  // namespace blaze
 
 #endif  // BAZEL_SRC_MAIN_CPP_BLAZE_UTIL_PLATFORM_H_
diff --git a/src/main/cpp/blaze_util_posix.cc b/src/main/cpp/blaze_util_posix.cc
index 3ac31a8573..44ad43cb17 100644
--- a/src/main/cpp/blaze_util_posix.cc
+++ b/src/main/cpp/blaze_util_posix.cc
@@ -60,4 +60,8 @@ void ExecuteProgram(const string &exe, const vector<string> &args_vector) {
 std::string ConvertPath(const std::string &path) { return path; }
 
 std::string ListSeparator() { return ":"; }
+
+bool SymlinkDirectories(const string &target, const string &link) {
+  return symlink(target.c_str(), link.c_str()) == 0;
+}
 }   // namespace blaze.