From 87cb3250cdc8f57732e245ad2adf54bf53f638ca Mon Sep 17 00:00:00 2001
From: "Roger A. Light" <roger@atchoo.org>
Date: Sun, 16 Oct 2022 08:12:26 +0100
Subject: [PATCH] Set C99 as the explicit, not implicit, build standard.

---
 CMakeLists.txt | 3 +++
 ChangeLog.txt  | 1 +
 config.mk      | 2 +-
 3 files changed, 5 insertions(+), 1 deletion(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 07b24642..6f78402a 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -13,6 +13,9 @@ project(mosquitto
 	LANGUAGES C CXX
 )
 
+set(CMAKE_C_STANDARD 11)
+set(CMAKE_C_STANDARD_REQUIRED ON)
+
 list(APPEND CMAKE_MODULE_PATH "${PROJECT_SOURCE_DIR}/cmake/")
 
 add_definitions (-DCMAKE -DVERSION=\"${VERSION}\")
diff --git a/ChangeLog.txt b/ChangeLog.txt
index 0bf0c0f4..2aaee403 100644
--- a/ChangeLog.txt
+++ b/ChangeLog.txt
@@ -160,6 +160,7 @@ Build:
 - Increased CMake minimal required version to 3.14, which is required for the
   preinstalled SQLite3 find module.
 - Add an CMake option `WITH_LTO` to enable/disable link time optimization.
+- Set C99 as the explicit, rather than implicit, build standard.
 
 
 2.0.15 - 2022-08-16
diff --git a/config.mk b/config.mk
index 7aac8cb8..c9f30d7e 100644
--- a/config.mk
+++ b/config.mk
@@ -164,7 +164,7 @@ ifeq ($(UNAME),SunOS)
 		CFLAGS?=-Wall -ggdb -O2
 	endif
 else
-	CFLAGS?=-Wall -ggdb -O3 -Wconversion -Wextra
+	CFLAGS?=-Wall -ggdb -O3 -Wconversion -Wextra -std=gnu99
 endif
 
 STATIC_LIB_DEPS:=