From a7a895b1785f466f3f946e821f80dbe7b0a0f9e9 Mon Sep 17 00:00:00 2001
From: Tim Wojtulewicz <tim@corelight.com>
Date: Tue, 11 Apr 2023 14:35:56 -0700
Subject: [PATCH] Only use -Wno-changes-meaning if it exists

---
 auxil/spicy/CMakeLists.txt | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/auxil/spicy/CMakeLists.txt b/auxil/spicy/CMakeLists.txt
index 4415f84521..d5bdd87022 100644
--- a/auxil/spicy/CMakeLists.txt
+++ b/auxil/spicy/CMakeLists.txt
@@ -24,7 +24,16 @@ endif ()
 # set these flags we do need a customizable subdirectory above the Spicy
 # sources.
 set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-missing-braces")
-set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-vla -Wno-changes-meaning")
+set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-vla")
+
+# GCC 13 adds a new flag to check whether a symbol changes meaning. Due to an issue in one
+# of the dependencies used by Spicy, this causes Zeek to fail to build on that compiler.
+# Until this is fixed, ignore that warning, but check to to make sure the flag exists first.
+include(CheckCXXCompilerFlag)
+check_cxx_compiler_flag("-Wno-changes-meaning" _has_no_changes_meaning_flag)
+if ( _has_no_changes_meaning_flag )
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-changes-meaning")
+endif ()
 
 # The script generating precompiled headers for Spicy expects a different build
 # system layout than provided for a bundled Spicy, disable it.