From 23e1453cd0cd43f81d60292cc187076d41c6370e Mon Sep 17 00:00:00 2001
From: Carlo Piovesan <piovesan.carlo@gmail.com>
Date: Fri, 27 Oct 2023 14:06:03 +0200
Subject: [PATCH] Revert "Merge pull request #9364 from
 taniabogatsch/increase-cmake-version"

This reverts commit 2646836f6fa6b47b41b2db0a96f4e9f95a4c6449, reversing
changes made to 71272844695fb7169beeeca23bd8f75e5434c204.
---
 CMakeLists.txt                         | 16 +++++++++++++---
 extension/parquet/CMakeLists.txt       |  2 +-
 third_party/imdb/CMakeLists.txt        |  2 +-
 third_party/libpg_query/CMakeLists.txt |  2 +-
 third_party/re2/CMakeLists.txt         |  3 ++-
 5 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 359f70d49c41..b38ff6c350eb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 2.8.12)
 
 if(POLICY CMP0026)
   cmake_policy(SET CMP0026 NEW)
@@ -22,7 +22,12 @@ find_package(Threads REQUIRED)
 
 set(CMAKE_EXPORT_COMPILE_COMMANDS ON)
 
-set (CMAKE_CXX_STANDARD 11)
+if (CMAKE_VERSION VERSION_LESS "3.1")
+    set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
+else ()
+  set (CMAKE_CXX_STANDARD 11)
+endif ()
+
 
 set(CMAKE_CXX_STANDARD_REQUIRED ON)
 set(CMAKE_CXX_EXTENSIONS OFF)
@@ -624,7 +629,12 @@ function(link_extension_libraries LIBRARY)
 endfunction()
 
 function(link_threads LIBRARY)
+  if (CMAKE_VERSION VERSION_LESS "3.1")
+    target_link_libraries(${LIBRARY} pthread)
+
+  else()
     target_link_libraries(${LIBRARY} Threads::Threads)
+  endif()
 endfunction()
 
 function(build_loadable_extension_directory NAME OUTPUT_DIRECTORY PARAMETERS)
@@ -1084,7 +1094,7 @@ if (NOT "${LOCAL_EXTENSION_REPO}" STREQUAL "")
   message(STATUS "Extensions will be deployed to: ${LOCAL_EXTENSION_REPO}")
 endif()
 
-if (NOT EXTENSION_CONFIG_BUILD )
+if (CMAKE_VERSION VERSION_GREATER "3.0" AND NOT EXTENSION_CONFIG_BUILD ) # this does not work with 2.8
 # Write the export set for build and install tree
 install(EXPORT "${DUCKDB_EXPORT_SET}" DESTINATION "${INSTALL_CMAKE_DIR}")
 export(EXPORT "${DUCKDB_EXPORT_SET}"
diff --git a/extension/parquet/CMakeLists.txt b/extension/parquet/CMakeLists.txt
index 1ef3305093f4..877ddf8689e5 100644
--- a/extension/parquet/CMakeLists.txt
+++ b/extension/parquet/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 2.8.12)
 
 project(ParquetExtension)
 
diff --git a/third_party/imdb/CMakeLists.txt b/third_party/imdb/CMakeLists.txt
index 5d10dde6d2de..2875dd87ff89 100644
--- a/third_party/imdb/CMakeLists.txt
+++ b/third_party/imdb/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 2.8.12)
 
 if(POLICY CMP0063)
     cmake_policy(SET CMP0063 NEW)
diff --git a/third_party/libpg_query/CMakeLists.txt b/third_party/libpg_query/CMakeLists.txt
index 5cb0aa6f6140..cb1e13d07191 100644
--- a/third_party/libpg_query/CMakeLists.txt
+++ b/third_party/libpg_query/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.5)
+cmake_minimum_required(VERSION 2.8.12)
 
 project(duckdb_pg_query CXX C)
 if(POLICY CMP0063)
diff --git a/third_party/re2/CMakeLists.txt b/third_party/re2/CMakeLists.txt
index df428ac1ea07..e7a7f586c79a 100644
--- a/third_party/re2/CMakeLists.txt
+++ b/third_party/re2/CMakeLists.txt
@@ -1,7 +1,8 @@
 # Copyright 2015 The RE2 Authors.  All Rights Reserved. Use of this source code
 # is governed by a BSD-style license that can be found in the LICENSE file.
 
-cmake_minimum_required(VERSION 3.5)
+# Old enough to support Ubuntu Trusty.
+cmake_minimum_required(VERSION 2.8.12)
 
 if(POLICY CMP0048)
   cmake_policy(SET CMP0048 NEW)