1 files changed, 4 insertions, 1 deletions
diff --git a/lib/Tooling/JSONCompilationDatabase.cpp b/lib/Tooling/JSONCompilationDatabase.cpp
index 3414f7db58..0ee9d174b4 100644
--- a/lib/Tooling/JSONCompilationDatabase.cpp
+++ b/lib/Tooling/JSONCompilationDatabase.cpp
@@ -190,8 +190,11 @@ std::unique_ptr<JSONCompilationDatabase>
 JSONCompilationDatabase::loadFromFile(StringRef FilePath,
                                       std::string &ErrorMessage,
                                       JSONCommandLineSyntax Syntax) {
+  // Don't mmap: if we're a long-lived process, the build system may overwrite.
   llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>> DatabaseBuffer =
-      llvm::MemoryBuffer::getFile(FilePath);
+      llvm::MemoryBuffer::getFile(FilePath, /*FileSize=*/-1,
+                                  /*RequiresNullTerminator=*/true,
+                                  /*IsVolatile=*/true);
   if (std::error_code Result = DatabaseBuffer.getError()) {
     ErrorMessage = "Error while opening JSON database: " + Result.message();
     return nullptr;