From 51b299cba0cde3c27817309eb48a3d7f890967e9 Mon Sep 17 00:00:00 2001
From: Haoyang Liu <liuhaoyang@pku.edu.cn>
Date: Sun, 28 Mar 2021 20:15:33 +0800
Subject: [PATCH] CMake : add C99 standard, move to CMake3 (#298)

* update CMakeLists.txt:
- add C99 standard checking to `CMakeLists.txt`
  older compilers may not enable this by default.
- change minimum cmake version to 3.0
  cmake2 does not recognize `add_library(... INTERFACE ...)`

* update CHANGES
---
 CHANGES        | 4 ++++
 CMakeLists.txt | 6 +++++-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/CHANGES b/CHANGES
index ff1133598..8c03629f7 100644
--- a/CHANGES
+++ b/CHANGES
@@ -1,5 +1,9 @@
 arpack-ng - 3.9.0
 
+[ Haoyang Liu ]
+ * CMake: minimum required version changed to 3.0
+ * CMake: add C99 standard checking
+
 [ Robert Schütz ]
  * use CMAKE_INSTALL_FULL_<dir> in arpack.pc
 
diff --git a/CMakeLists.txt b/CMakeLists.txt
index c9d23f459..98224cc0f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 2.8.6)
+cmake_minimum_required(VERSION 3.0)
 
 if (NOT DEFINED CMAKE_BUILD_TYPE)
    set (CMAKE_BUILD_TYPE Release CACHE STRING "Build type")
@@ -13,6 +13,10 @@ set(arpack_ng_VERSION ${arpack_ng_MAJOR_VERSION}.${arpack_ng_MINOR_VERSION}.${ar
 
 set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} ${PROJECT_SOURCE_DIR}/cmake)
 
+# set C99 standard
+set(CMAKE_C_STANDARD 99)
+set(CMAKE_C_STANDARD_REQUIRED True)
+
 # Adopted from https://github.com/feymark/arpack.git
 
 if (POLICY CMP0042)