[Support] fix TempFile infinite loop and permission denied errors

Summary:
On Windows, TempFile::create() was prone to failing with permission
denied errors when a process created many tempfiles without providing
a model large enough to accommodate them. There was also a problem
with createUniqueEntity getting into an infinite loop when all names
permitted by the model are in use. This change fixes both of these
problems and adds a unit test for them.

Reviewers: pcc, rnk, zturner

Reviewed By: zturner

Subscribers: inglorion, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D50126

llvm-svn: 338745

1 files changed, 31 insertions, 0 deletions

diff --git a/llvm/unittests/Support/Path.cpp b/llvm/unittests/Support/Path.cpp
index dc5bfb8c7bd..158d6cfa3c3 100644
--- a/llvm/unittests/Support/Path.cpp
+++ b/llvm/unittests/Support/Path.cpp
@@ -681,6 +681,37 @@ TEST_F(FileSystemTest, TempFiles) {
 #endif
 }
 
+TEST_F(FileSystemTest, TempFileCollisions) {
+  SmallString<128> TestDirectory;
+  ASSERT_NO_ERROR(
+      fs::createUniqueDirectory("CreateUniqueFileTest", TestDirectory));
+  FileRemover Cleanup(TestDirectory);
+  SmallString<128> Model = TestDirectory;
+  path::append(Model, "%.tmp");
+  SmallString<128> Path;
+  std::vector<fs::TempFile> TempFiles;
+
+  auto TryCreateTempFile = [&]() {
+    Expected<fs::TempFile> T = fs::TempFile::create(Model);
+    if (T) {
+      TempFiles.push_back(std::move(*T));
+      return true;
+    } else {
+      logAllUnhandledErrors(T.takeError(), errs(),
+                            "Failed to create temporary file: ");
+      return false;
+    }
+  };
+
+  // We should be able to create exactly 16 temporary files.
+  for (int i = 0; i < 16; ++i)
+    EXPECT_TRUE(TryCreateTempFile());
+  EXPECT_FALSE(TryCreateTempFile());
+
+  for (fs::TempFile &T : TempFiles)
+    cantFail(T.discard());
+}
+
 TEST_F(FileSystemTest, CreateDir) {
   ASSERT_NO_ERROR(fs::create_directory(Twine(TestDirectory) + "foo"));
   ASSERT_NO_ERROR(fs::create_directory(Twine(TestDirectory) + "foo"));