From 39d46395d0634ac56e33b70670f55326240d81db Mon Sep 17 00:00:00 2001
From: Catherine <whitequark@whitequark.org>
Date: Wed, 22 Jan 2025 21:47:38 +0000
Subject: [PATCH] CMake: disallow in-tree builds.

In-tree builds pollute the source directory and make version control
more difficult to use effectively.
---
 CMakeLists.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 31073c87..735494bc 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,3 +1,7 @@
+if (CMAKE_BINARY_DIR STREQUAL CMAKE_SOURCE_DIR)
+    message(FATAL_ERROR "In-tree builds are not supported. Instead, run:\ncmake . -B build <options> && cmake --build build")
+endif()
+
 cmake_minimum_required(VERSION 3.25)
 project(nextpnr CXX)