From 0b6d0ea50782acc5b82a757c93a9e015d68fb3ce Mon Sep 17 00:00:00 2001
From: Danny Robson <danny@nerdcruft.net>
Date: Tue, 23 Aug 2022 13:35:26 +1000
Subject: [PATCH] compile_flag: add multiple flag search

---
 compile_flag.cmake | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/compile_flag.cmake b/compile_flag.cmake
index f6bb622..deff396 100644
--- a/compile_flag.cmake
+++ b/compile_flag.cmake
@@ -9,6 +9,11 @@ include(CMakeCheckCompilerFlagCommonPatterns)
 # -fsanitize=address is impossible with this macro.
 #
 # Instead, we roll out own. Yay cmake...
+#
+# Accepts a second parameter that names an output variable. It will be set to
+# 1 if-and-only-if the flag was accepted by the compiler. Otherwise it will be
+# left untouched. It is up to the user to reset this flag between invocations
+# if necessary.
 macro (append_compile_flag _flag)
     string (MAKE_C_IDENTIFIER ${_flag} _name)
 
@@ -48,5 +53,32 @@ macro (append_compile_flag _flag)
 
     if (compile_flag_${_name})
         set (CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} ${_flag}")
+        if (${ARGC} GREATER_EQUAL 2)
+            set(${ARGV1} 1)
+        endif()
     endif()
 endmacro(append_compile_flag)
+
+
+# Find the first compile flag in the list of arguments that is supported by
+# the compiler and set it.
+macro (append_first_compile_flag)
+    message(CHECK_START "First CXXFLAGS ${ARGV}")
+    foreach(__append_first_compile_flag__flag ${ARGV})
+        set(__append_first_compile_flag__test 0)
+
+        append_compile_flag(
+            ${__append_first_compile_flag__flag}
+            __append_first_compile_flag__test
+        )
+
+        if (${__append_first_compile_flag__test})
+            message(CHECK_PASS "Found ${__append_first_compile_flag__flag}")
+            break()
+        endif()
+    endforeach()
+
+    if (NOT ${__append_first_compile_flag__test})
+        message(CHECK_FAIL "No valid flags")
+    endif ()
+endmacro()
\ No newline at end of file