From 73be1ac6c1ba766af280ddadedde0306a9decd79 Mon Sep 17 00:00:00 2001
From: Sam McCall <sam.mccall@gmail.com>
Date: Tue, 7 May 2019 09:05:15 +0000
Subject: [PATCH] [Tooling] Don't mmap the JSONCompilationDatabase, it's not
 correct for long-lived processes.

Reviewers: ilya-biryukov

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D61631

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@360122 91177308-0d34-0410-b5e6-96231b3b80d8
---
 lib/Tooling/JSONCompilationDatabase.cpp | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

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;
-- 
2.50.1