Bazel client, Windows: CreateDirectoryW path limit

Fix the path limit for non-UNC-prefixed paths when
using CreateDirectoryW. According to MSDN [1],
this is only 248 chars, as opposed to the usual
260 (MAX_PATH).

See https://github.com/bazelbuild/bazel/issues/2107

[1] https://msdn.microsoft.com/en-us/library/windows/desktop/aa363855(v=vs.85).aspx

--
PiperOrigin-RevId: 149627964
MOS_MIGRATED_REVID=149627964

src/main/cpp/util/file_platform.h

diff --git a/src/main/cpp/util/file_platform.h b/src/main/cpp/util/file_platform.h
index 7733e7a..50b75de 100644
--- a/src/main/cpp/util/file_platform.h
+++ b/src/main/cpp/util/file_platform.h
@@ -205,7 +205,8 @@
 
 #if defined(COMPILER_MSVC) || defined(__CYGWIN__)
 // Like `AsWindowsPath` but the result is absolute and has UNC prefix if needed.
-bool AsWindowsPathWithUncPrefix(const std::string &path, std::wstring *wpath);
+bool AsWindowsPathWithUncPrefix(const std::string &path, std::wstring *wpath,
+                                size_t max_path = 260 /* MAX_PATH */);
 
 // Same as `AsWindowsPath`, but returns a lowercase 8dot3 style shortened path.
 // Result will never have a UNC prefix, nor a trailing "/" or "\".

src/main/cpp/util/file_windows.cc

diff --git a/src/main/cpp/util/file_windows.cc b/src/main/cpp/util/file_windows.cc
index f763f9e..5159917 100644
--- a/src/main/cpp/util/file_windows.cc
+++ b/src/main/cpp/util/file_windows.cc
@@ -101,8 +101,8 @@
   return CharTraits<char_type>::IsAlpha(ch[0]) && ch[1] == ':';
 }
 
-static void AddUncPrefixMaybe(wstring* path) {
-  if (path->size() >= MAX_PATH && !HasUncPrefix(path->c_str())) {
+static void AddUncPrefixMaybe(wstring* path, size_t max_path = MAX_PATH) {
+  if (path->size() >= max_path && !HasUncPrefix(path->c_str())) {
     *path = wstring(L"\\\\?\\") + *path;
   }
 }
@@ -483,7 +483,8 @@
   return true;
 }
 
-bool AsWindowsPathWithUncPrefix(const string& path, wstring* wpath) {
+bool AsWindowsPathWithUncPrefix(const string& path, wstring* wpath,
+                                size_t max_path) {
   if (IsDevNull(path)) {
     wpath->assign(L"NUL");
     return true;
@@ -497,7 +498,7 @@
   if (!IsAbsolute(path)) {
     wpath->assign(wstring(GetCwdW().get()) + L"\\" + *wpath);
   }
-  AddUncPrefixMaybe(wpath);
+  AddUncPrefixMaybe(wpath, max_path);
   return true;
 }
 
@@ -1120,7 +1121,9 @@
     return false;
   }
   wstring wpath;
-  if (!AsWindowsPathWithUncPrefix(path, &wpath)) {
+  // According to MSDN, CreateDirectory's limit without the UNC prefix is
+  // 248 characters (so it could fit another filename before reaching MAX_PATH).
+  if (!AsWindowsPathWithUncPrefix(path, &wpath, 248)) {
     return false;
   }
   return MakeDirectoriesW(wpath);