From 8a0ab2de48f41edf66a855dbc856fcf14c7446d9 Mon Sep 17 00:00:00 2001
From: Andy Green <andy@warmcat.com>
Date: Wed, 15 May 2019 07:27:18 +0100
Subject: [PATCH] cmake: probe gcc flags capability

old gcc doesn't have some of the extended warning flags we want to apply...
use cmake to confirm the gcc has them before trying to use them.
---
 CMakeLists.txt | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 15a0f9765..e70522e35 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1369,10 +1369,21 @@ if (CMAKE_COMPILER_IS_GNUCC OR CMAKE_COMPILER_IS_GNUCXX OR (CMAKE_C_COMPILER_ID
 		message("Enabling ASAN")
 	endif()
 
+	check_c_compiler_flag("-Wignored-qualifiers" LWS_GCC_HAS_IGNORED_QUALIFIERS)
+	check_c_compiler_flag("-Wtype-limits" LWS_GCC_HAS_TYPE_LIMITS)
+
+	if (LWS_GCC_HAS_IGNORED_QUALIFIERS)
+		set(CMAKE_C_FLAGS "-Wignored-qualifiers ${CMAKE_C_FLAGS}" )
+	endif()
+
+	if (LWS_GCC_HAS_TYPE_LIMITS)
+		set(CMAKE_C_FLAGS "-Wtype-limits ${CMAKE_C_FLAGS}" )
+	endif()
+
     if (UNIX AND NOT LWS_WITH_ESP32)
-	    set(CMAKE_C_FLAGS "-Wall -Wsign-compare -Wignored-qualifiers -Wtype-limits -Wuninitialized -Werror ${VISIBILITY_FLAG} -Wundef ${GCOV_FLAGS} ${CMAKE_C_FLAGS} ${ASAN_FLAGS}" )
+	    set(CMAKE_C_FLAGS "-Wall -Wsign-compare -Wuninitialized -Werror ${VISIBILITY_FLAG} -Wundef ${GCOV_FLAGS} ${CMAKE_C_FLAGS} ${ASAN_FLAGS}" )
     else()
-	    set(CMAKE_C_FLAGS "-Wall -Wsign-compare -Wignored-qualifiers -Wtype-limits -Wuninitialized -Werror ${VISIBILITY_FLAG} ${GCOV_FLAGS} ${CMAKE_C_FLAGS}" )
+	    set(CMAKE_C_FLAGS "-Wall -Wsign-compare -Wuninitialized -Werror ${VISIBILITY_FLAG} ${GCOV_FLAGS} ${CMAKE_C_FLAGS}" )
     endif()
 endif ()