From aff63306e0a2844907b06c5d2de1339e597b794f Mon Sep 17 00:00:00 2001
From: Antoine Pitrou <antoine@python.org>
Date: Thu, 20 Jan 2022 12:47:57 +0100
Subject: [PATCH 1/2] ARROW-15388: [C++] Avoid including absl from flatbuffers

There may be an incomplete/broken copy of the Abseil library lying around
(for example because of a race condition while installing it as a bundled library).

Since absl is only used by Flatbuffers to provide a string_view facility,
use our own vendored string_view instead.
---
 cpp/thirdparty/flatbuffers/README.md          | 44 +++++++++++++++++++
 .../flatbuffers/include/flatbuffers/base.h    |  8 ++--
 2 files changed, 48 insertions(+), 4 deletions(-)
 create mode 100644 cpp/thirdparty/flatbuffers/README.md

diff --git a/cpp/thirdparty/flatbuffers/README.md b/cpp/thirdparty/flatbuffers/README.md
new file mode 100644
index 000000000000..f99980a1e641
--- /dev/null
+++ b/cpp/thirdparty/flatbuffers/README.md
@@ -0,0 +1,44 @@
+<!---
+  Licensed to the Apache Software Foundation (ASF) under one
+  or more contributor license agreements.  See the NOTICE file
+  distributed with this work for additional information
+  regarding copyright ownership.  The ASF licenses this file
+  to you under the Apache License, Version 2.0 (the
+  "License"); you may not use this file except in compliance
+  with the License.  You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+  Unless required by applicable law or agreed to in writing,
+  software distributed under the License is distributed on an
+  "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+  KIND, either express or implied.  See the License for the
+  specific language governing permissions and limitations
+  under the License.
+-->
+
+This directory contains a vendored version of Flatbuffers
+(unknown changeset), with the following patch for ARROW-15388:
+
+```diff
+diff --git a/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h b/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
+index 955738067..f8277b3e9 100644
+--- a/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
++++ b/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
+@@ -212,11 +212,11 @@ namespace flatbuffers {
+         typedef std::experimental::string_view string_view;
+       }
+       #define FLATBUFFERS_HAS_STRING_VIEW 1
+-    // Check for absl::string_view
+-    #elif __has_include("absl/strings/string_view.h")
+-      #include "absl/strings/string_view.h"
++    // Check for arrow::util::string_view
++    #elif __has_include("arrow/util/string_view.h")
++      #include "arrow/util/string_view.h"
+       namespace flatbuffers {
+-        typedef absl::string_view string_view;
++        typedef arrow::util::string_view string_view;
+       }
+       #define FLATBUFFERS_HAS_STRING_VIEW 1
+     #endif
+```
diff --git a/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h b/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
index 955738067234..f8277b3e9c6c 100644
--- a/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
+++ b/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
@@ -212,11 +212,11 @@ namespace flatbuffers {
         typedef std::experimental::string_view string_view;
       }
       #define FLATBUFFERS_HAS_STRING_VIEW 1
-    // Check for absl::string_view
-    #elif __has_include("absl/strings/string_view.h")
-      #include "absl/strings/string_view.h"
+    // Check for arrow::util::string_view
+    #elif __has_include("arrow/util/string_view.h")
+      #include "arrow/util/string_view.h"
       namespace flatbuffers {
-        typedef absl::string_view string_view;
+        typedef arrow::util::string_view string_view;
       }
       #define FLATBUFFERS_HAS_STRING_VIEW 1
     #endif

From 61e51033087a1a4cd9cc85599be7de966845b648 Mon Sep 17 00:00:00 2001
From: Antoine Pitrou <antoine@python.org>
Date: Thu, 20 Jan 2022 16:14:13 +0100
Subject: [PATCH 2/2] Remove arrow::util::string_view fallback

---
 cpp/thirdparty/flatbuffers/README.md             | 16 +++++++---------
 .../flatbuffers/include/flatbuffers/base.h       |  7 -------
 2 files changed, 7 insertions(+), 16 deletions(-)

diff --git a/cpp/thirdparty/flatbuffers/README.md b/cpp/thirdparty/flatbuffers/README.md
index f99980a1e641..e955adba4ceb 100644
--- a/cpp/thirdparty/flatbuffers/README.md
+++ b/cpp/thirdparty/flatbuffers/README.md
@@ -22,23 +22,21 @@ This directory contains a vendored version of Flatbuffers
 
 ```diff
 diff --git a/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h b/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
-index 955738067..f8277b3e9 100644
+index 955738067..fccce42f6 100644
 --- a/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
 +++ b/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
-@@ -212,11 +212,11 @@ namespace flatbuffers {
+@@ -212,13 +212,6 @@ namespace flatbuffers {
          typedef std::experimental::string_view string_view;
        }
        #define FLATBUFFERS_HAS_STRING_VIEW 1
 -    // Check for absl::string_view
 -    #elif __has_include("absl/strings/string_view.h")
 -      #include "absl/strings/string_view.h"
-+    // Check for arrow::util::string_view
-+    #elif __has_include("arrow/util/string_view.h")
-+      #include "arrow/util/string_view.h"
-       namespace flatbuffers {
+-      namespace flatbuffers {
 -        typedef absl::string_view string_view;
-+        typedef arrow::util::string_view string_view;
-       }
-       #define FLATBUFFERS_HAS_STRING_VIEW 1
+-      }
+-      #define FLATBUFFERS_HAS_STRING_VIEW 1
      #endif
+   #endif // __has_include
+ #endif // !FLATBUFFERS_HAS_STRING_VIEW
 ```
diff --git a/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h b/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
index f8277b3e9c6c..fccce42f68aa 100644
--- a/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
+++ b/cpp/thirdparty/flatbuffers/include/flatbuffers/base.h
@@ -212,13 +212,6 @@ namespace flatbuffers {
         typedef std::experimental::string_view string_view;
       }
       #define FLATBUFFERS_HAS_STRING_VIEW 1
-    // Check for arrow::util::string_view
-    #elif __has_include("arrow/util/string_view.h")
-      #include "arrow/util/string_view.h"
-      namespace flatbuffers {
-        typedef arrow::util::string_view string_view;
-      }
-      #define FLATBUFFERS_HAS_STRING_VIEW 1
     #endif
   #endif // __has_include
 #endif // !FLATBUFFERS_HAS_STRING_VIEW