From: Soeren Apel <redacted>
Date: Fri, 8 Sep 2023 19:15:11 +0000 (+0200)
Subject: Fix CMake CXX_STANDARD handling
X-Git-Url: https://sigrok.org/gitaction?a=commitdiff_plain;h=cb40d40c6c60f2b1bec744ad946253e3d8c56c13;p=pulseview.git

Fix CMake CXX_STANDARD handling

https://sigrok.org/gitweb/?p=pulseview.git;a=commit;f=CMakeLists.txt;h=fa8d0fcb4cff4f19943fe3ff152dc1428b400b01 introduced a CXX_STANDARD value of 17 while still only requiring cmake 2.8.12.

However, https://cmake.org/cmake/help/latest/prop_tgt/CXX_STANDARD.html#cxx-standard shows that a value of 17 was introduced with cmake 3.8, leading to

"CXX_STANDARD is set to invalid value '17'" when trying to build with cmake < 3.8.

Hence, for versions below 3.8, we only check for up to 14.
---

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 395222a2..c206d915 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -83,23 +83,39 @@ include(memaccess)
 
 find_package(PkgConfig)
 
-check_cxx_compiler_flag("-std=c++17" HAVE_STD_CXX_17)
-check_cxx_compiler_flag("-std=c++14" HAVE_STD_CXX_14)
-check_cxx_compiler_flag("-std=c++11" HAVE_STD_CXX_11)
-if(HAVE_STD_CXX_17)
-	message(STATUS "Using C++17 for the application build")
-	set(CMAKE_CXX_STANDARD 17)
-	set(REQUIRED_STD_CXX_FLAGS "-std=c++17")
-elseif(HAVE_STD_CXX_14)
-	message(STATUS "Using C++14 for the application build")
-	set(CMAKE_CXX_STANDARD 14)
-	set(REQUIRED_STD_CXX_FLAGS "-std=c++14")
-elseif(HAVE_STD_CXX_11)
-	message(STATUS "Using C++11 for the application build")
-	set(CMAKE_CXX_STANDARD 11)
-	set(REQUIRED_STD_CXX_FLAGS "-std=c++11")
+if(${CMAKE_VERSION} VERSION_GREATER_EQUAL "3.8.0")
+	check_cxx_compiler_flag("-std=c++17" HAVE_STD_CXX_17)
+	check_cxx_compiler_flag("-std=c++14" HAVE_STD_CXX_14)
+	check_cxx_compiler_flag("-std=c++11" HAVE_STD_CXX_11)
+	if(HAVE_STD_CXX_17)
+		message(STATUS "Using C++17 for the application build")
+		set(CMAKE_CXX_STANDARD 17)
+		set(REQUIRED_STD_CXX_FLAGS "-std=c++17")
+	elseif(HAVE_STD_CXX_14)
+		message(STATUS "Using C++14 for the application build")
+		set(CMAKE_CXX_STANDARD 14)
+		set(REQUIRED_STD_CXX_FLAGS "-std=c++14")
+	elseif(HAVE_STD_CXX_11)
+		message(STATUS "Using C++11 for the application build")
+		set(CMAKE_CXX_STANDARD 11)
+		set(REQUIRED_STD_CXX_FLAGS "-std=c++11")
+	else()
+		message(FATAL_ERROR "Need modern C++, at least language standard 11")
+	endif()
 else()
-	message(FATAL_ERROR "Need modern C++, at least language standard 11")
+	check_cxx_compiler_flag("-std=c++14" HAVE_STD_CXX_14)
+	check_cxx_compiler_flag("-std=c++11" HAVE_STD_CXX_11)
+	if(HAVE_STD_CXX_14)
+		message(STATUS "Using C++14 for the application build")
+		set(CMAKE_CXX_STANDARD 14)
+		set(REQUIRED_STD_CXX_FLAGS "-std=c++14")
+	elseif(HAVE_STD_CXX_11)
+		message(STATUS "Using C++11 for the application build")
+		set(CMAKE_CXX_STANDARD 11)
+		set(REQUIRED_STD_CXX_FLAGS "-std=c++11")
+	else()
+		message(FATAL_ERROR "Need modern C++, at least language standard 11")
+	endif()
 endif()
 
 list(APPEND PKGDEPS glib-2.0>=2.28.0)