From b72d21202402a603db6d512fb9271cfa83249639 Mon Sep 17 00:00:00 2001
From: Hans Jansen <hansjansen162@outlook.com>
Date: Thu, 22 Jun 2023 19:49:30 +0200
Subject: [PATCH] Add ifunc check to CMakeLists.txt

CMake build system will now verify if __attribute__((__ifunc__())) can be
used in the build system. If so, HAVE_FUNC_ATTRIBUTE_IFUNC will be
defined to 1.
---
 CMakeLists.txt | 19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 458ad49d..fb5d2582 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -763,6 +763,25 @@ check_c_source_compiles("
 cmake_pop_check_state()
 tuklib_add_definition_if(liblzma HAVE_FUNC_ATTRIBUTE_CONSTRUCTOR)
 
+# Check for __attribute__((__ifunc__())) support.
+option(CHECK_ATTR_IFUNC "Use __attribute__((__ifunc__())) if supported by \
+the system" ON)
+
+if (CHECK_ATTR_IFUNC)
+    cmake_push_check_state()
+    set(CMAKE_REQUIRED_FLAGS "-Werror")
+    check_c_source_compiles("
+            static void func(void) { return; }
+            static void (*resolve_func (void)) (void) { return func; }
+            void func_ifunc (void)
+                    __attribute__ ((__ifunc__ (\"resolve_func\")));
+            int main(void) { return 0; }
+        "
+        HAVE_FUNC_ATTRIBUTE_IFUNC)
+    cmake_pop_check_state()
+    tuklib_add_definition_if(liblzma HAVE_FUNC_ATTRIBUTE_IFUNC)
+endif()
+
 # cpuid.h
 check_include_file(cpuid.h HAVE_CPUID_H)
 tuklib_add_definition_if(liblzma HAVE_CPUID_H)