[Lldb-commits] [lldb] [lldb][test] Downgrade missing-libcxx check from error to warning (PR #199262)

[Med Ismail Bennani via lldb-commits]

https://github.com/medismailben created https://github.com/llvm/llvm-project/pull/199262

The cmake check that fails when LLDB_HAS_LIBCXX is OFF is too strict: the test infrastructure already handles the missing-libcxx case gracefully (lldb/test/API/lit.cfg.py only adds --libcxx-include-dir / --libcxx-library-dir to the dotest command when config.has_libcxx is true, otherwise dotest falls back to whatever libc++ the compiler picks up by default — system libc++ on Darwin).

Hard-failing the cmake configure means downstreams that intentionally opt out of building libc++ in-tree can't keep LLDB_INCLUDE_TESTS=ON to get the ninja check-lldb-* targets generated for tests they actually want to run (Shell tests, non-libc++ API tests, cloud-device tests, etc.).

Downgrade the SEND_ERROR to WARNING and rephrase the message so it reflects the actual fallback behavior instead of demanding the user either enable libcxx or disable tests outright.

>From 6b48ad3d49f194ed1f2a9051382da7d7dca4b31e Mon Sep 17 00:00:00 2001
From: Med Ismail Bennani <ismail at bennani.ma>
Date: Fri, 22 May 2026 12:22:15 -0700
Subject: [PATCH] [lldb][test] Downgrade missing-libcxx check from error to
 warning
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The cmake check that fails when LLDB_HAS_LIBCXX is OFF is too strict:
the test infrastructure already handles the missing-libcxx case
gracefully (lldb/test/API/lit.cfg.py only adds --libcxx-include-dir /
--libcxx-library-dir to the dotest command when config.has_libcxx is
true, otherwise dotest falls back to whatever libc++ the compiler
picks up by default — system libc++ on Darwin).

Hard-failing the cmake configure means downstreams that intentionally
opt out of building libc++ in-tree (e.g., to avoid running the
runtimes build in environments where it doesn't work) can't keep
LLDB_INCLUDE_TESTS=ON to get the ninja check-lldb-* targets generated
for tests they actually want to run (Shell tests, non-libc++ API
tests, cloud-device tests, etc.).

Downgrade the SEND_ERROR to WARNING and rephrase the message so it
reflects the actual fallback behavior instead of demanding the user
either enable libcxx or disable tests outright.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply at anthropic.com>
---
 lldb/test/CMakeLists.txt | 15 +++++++++------
 1 file changed, 9 insertions(+), 6 deletions(-)

diff --git a/lldb/test/CMakeLists.txt b/lldb/test/CMakeLists.txt
index ed9dcd11cc6cd..fdfa1fa83efef 100644
--- a/lldb/test/CMakeLists.txt
+++ b/lldb/test/CMakeLists.txt
@@ -205,13 +205,16 @@ if(TARGET clang)
             "LLDB_TEST_LIBCXX_ROOT_DIR to it.")
       endif()
     else()
-      # We require libcxx for the test suite, so if we aren't building it,
-      # provide a helpful error about how to resolve the situation.
+      # The LLDB test suite uses libc++ for many tests. If it isn't being
+      # built in-tree, warn and let the suite fall back to whatever libc++
+      # the compiler picks up by default (the system one on Darwin); the
+      # libc++-specific tests will be skipped or run against system libc++.
       if(NOT LLDB_HAS_LIBCXX)
-        message(SEND_ERROR
-          "LLDB test suite requires libc++, but it is currently disabled. "
-          "Please add `libcxx` to `LLVM_ENABLE_RUNTIMES` or disable tests via "
-          "`LLDB_INCLUDE_TESTS=OFF`.")
+        message(WARNING
+          "LLDB test suite normally uses an in-tree libc++; it is currently "
+          "disabled. libc++-specific tests will be skipped or fall back to the "
+          "system libc++. Add `libcxx` to `LLVM_ENABLE_RUNTIMES` to enable "
+          "the full test surface.")
       endif()
     endif()
   endif()