[libc-commits] [libc] e84566f - [libc] Fail fast when building standalone (#119426)

[via libc-commits]

Author: Carlo Cabrera
Date: 2024-12-12T17:17:17+08:00
New Revision: e84566ff2b8e9bb67ccc6764d7003871535e550e

URL: https://github.com/llvm/llvm-project/commit/e84566ff2b8e9bb67ccc6764d7003871535e550e
DIFF: https://github.com/llvm/llvm-project/commit/e84566ff2b8e9bb67ccc6764d7003871535e550e.diff

LOG: [libc] Fail fast when building standalone (#119426)

Building with the source directory rooted in the libc subdirectory isn't
tested in CI and can lead to subtle build problems (cf. #118871).

Let's fail fast with a helpful error message instead to help users
configure libc correctly.

Co-authored-by: Nick Desaulniers <nickdesaulniers at users.noreply.github.com>

Added: 
    

Modified: 
    libc/CMakeLists.txt

Removed: 
    


################################################################################
diff  --git a/libc/CMakeLists.txt b/libc/CMakeLists.txt
index 6d48489284faef..88cc75e83b043d 100644
--- a/libc/CMakeLists.txt
+++ b/libc/CMakeLists.txt
@@ -1,6 +1,12 @@
 cmake_minimum_required(VERSION 3.20.0)
 set(LLVM_SUBPROJECT_TITLE "libc")
 
+if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
+  message(FATAL_ERROR "Builds rooted in the libc directory are not supported. "
+    "Builds should be rooted in the runtimes directory instead. "
+    "Please see the documentation at https://libc.llvm.org/usage_modes.html for more info.")
+endif()
+
 # Include LLVM's cmake policies.
 if(NOT DEFINED LLVM_COMMON_CMAKE_UTILS)
   set(LLVM_COMMON_CMAKE_UTILS ${CMAKE_CURRENT_SOURCE_DIR}/../cmake)