From ec4c002faa350f02919fe0f710279d2922e254a1 Mon Sep 17 00:00:00 2001
From: Hennadii Stepanov <32963518+hebasto@users.noreply.github.com>
Date: Sat, 11 May 2024 11:13:41 +0100
Subject: [PATCH] cmake: Simplify `PROJECT_IS_TOP_LEVEL` emulation

Detecting whether it is the top level by comparing the value of
`CMAKE_SOURCE_DIR` with `CMAKE_CURRENT_SOURCE_DIR` is supported by all
versions of CMake and is a very common pattern.
---
 CMakeLists.txt | 10 ++++------
 1 file changed, 4 insertions(+), 6 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 27d6e643..fffa123d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -19,15 +19,13 @@ project(libsecp256k1
 
 if(CMAKE_VERSION VERSION_LESS 3.21)
   # Emulates CMake 3.21+ behavior.
-  get_directory_property(parent_directory PARENT_DIRECTORY)
-  if(parent_directory)
-    set(PROJECT_IS_TOP_LEVEL OFF)
-    set(${PROJECT_NAME}_IS_TOP_LEVEL OFF)
-  else()
+  if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
     set(PROJECT_IS_TOP_LEVEL ON)
     set(${PROJECT_NAME}_IS_TOP_LEVEL ON)
+  else()
+    set(PROJECT_IS_TOP_LEVEL OFF)
+    set(${PROJECT_NAME}_IS_TOP_LEVEL OFF)
   endif()
-  unset(parent_directory)
 endif()
 
 # The library version is based on libtool versioning of the ABI. The set of