Fix a relatively nasty bug with fs::getPathFromOpenFD() on Windows. The GetFinalPathNameByHandle API does not behave as documented; if given a buffer that has enough space for the path but not the null terminator, the call will return the number of characters required *without* the null terminator (despite being documented otherwise) and it will not set GetLastError(). The result was that this function would return a bogus path and no error. Instead, ensure there is sufficient space for a null terminator (we already strip it off manually for compatibility with older versions of Windows).

llvm-svn: 273195

1 files changed, 13 insertions, 4 deletions

diff --git a/llvm/lib/Support/Windows/Path.inc b/llvm/lib/Support/Windows/Path.inc
index 5f588d7884e..8e5931ce6d8 100644
--- a/llvm/lib/Support/Windows/Path.inc
+++ b/llvm/lib/Support/Windows/Path.inc
@@ -821,11 +821,19 @@ std::error_code getPathFromOpenFD(int FD, SmallVectorImpl<char> &ResultPath) {
 
   DWORD CharCount;
   do {
+    // FIXME: We should be using the W version of this API and converting the
+    // resulting path to UTF-8 to handle non-ASCII file paths.
     CharCount = ::GetFinalPathNameByHandleA(FileHandle, ResultPath.begin(),
-                                            ResultPath.capacity(), FILE_NAME_NORMALIZED);
-    if (CharCount <= ResultPath.capacity())
+                                            ResultPath.capacity(),
+                                            FILE_NAME_NORMALIZED);
+    if (CharCount < ResultPath.capacity())
       break;
-    ResultPath.reserve(CharCount);
+
+    // Reserve sufficient space for the path as well as the null character. Even
+    // though the API does not document that it is required, if we reserve just
+    // CharCount space, the function call will not store the resulting path and
+    // still report success.
+    ResultPath.reserve(CharCount + 1);
   } while (true);
 
   if (CharCount == 0)
@@ -833,7 +841,8 @@ std::error_code getPathFromOpenFD(int FD, SmallVectorImpl<char> &ResultPath) {
 
   ResultPath.set_size(CharCount);
 
-  // On earlier Windows releases, the character count includes the terminating null.
+  // On earlier Windows releases, the character count includes the terminating
+  // null.
   if (ResultPath.back() == '\0')
     ResultPath.pop_back();