[Lldb-commits] [lldb] [lldb][cmake] Error out when building debugserver with CMake 4 (PR #138020)

[Chelsea Cassanova via lldb-commits]

https://github.com/chelcassanova created https://github.com/llvm/llvm-project/pull/138020

CMake 4 no longer sets the `CMAKE_OSX_SYSROOT` variable by default. If you've updated to CMake 4 on macOS (e.g. with brew) and try building LLDB with CMake/ninja, this will yield an error when building debugserver that clang is unable to run since it tries to compile files that don't exist.

These files are supposed to be generated by the `mig` process. `mig` needs the `CMAKE_OSX_SYSROOT` variable in order to work and without it, it silently fails to generate the files that later on need to be compiled.

This commit will fatal error out of config when building debugserver without having set CMAKE_OSX_SYSROOT.

>From df5306b9ba433a907795a74f939c283a857f0063 Mon Sep 17 00:00:00 2001
From: Chelsea Cassanova <chelsea_cassanova at apple.com>
Date: Mon, 28 Apr 2025 10:28:03 -0700
Subject: [PATCH] [lldb][cmake] Error out when building debugserver with CMake
 4

CMake 4 no longer sets the `CMAKE_OSX_SYSROOT` variable by default. If
you've updated to CMake 4 on macOS (e.g. with brew) and try building LLDB with
CMake/ninja, this will yield an error when building debugserver that
clang is unable to run since it tries to compile files that don't exist.

These files are supposed to be generated by the `mig` process. `mig`
needs the `CMAKE_OSX_SYSROOT` variable in order to work and without it,
it silently fails to generate the files that later on need to be
compiled.

This commit will fatal error out of config when building debugserver
without having set CMAKE_OSX_SYSROOT.
---
 lldb/tools/debugserver/source/CMakeLists.txt | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/lldb/tools/debugserver/source/CMakeLists.txt b/lldb/tools/debugserver/source/CMakeLists.txt
index 1a433898f6aa4..45b16c74f5197 100644
--- a/lldb/tools/debugserver/source/CMakeLists.txt
+++ b/lldb/tools/debugserver/source/CMakeLists.txt
@@ -154,6 +154,10 @@ endif()
 
 add_definitions(-DLLDB_USE_OS_LOG)
 
+if(NOT CMAKE_OSX_SYSROOT)
+  message(FATAL_ERROR "debugserver needs the macOS SDK root. Please pass in -DCMAKE_OSX_SYSROOT in your CMake invocation")
+endif()
+
 if(${CMAKE_OSX_SYSROOT} MATCHES ".Internal.sdk$")
   message(STATUS "LLDB debugserver energy support is enabled")
   add_definitions(-DLLDB_ENERGY)