[Mlir-commits] [mlir] [MLIR][CMake] Fix LLVM_DEFINITIONS handling in standalone example (PR #234653)

[Christopher Bate]

https://github.com/christopherbate created https://github.com/llvm/llvm-project/pull/234653

Split LLVM_DEFINITIONS into a CMake list before passing it to add_definitions(), and apply it before HandleLLVMOptions overwrites the variable.

Add comments explaining the compile and linker flag setup and how to scope HandleLLVMOptions around third-party dependencies.


>From d180d309b36d7387b3c34353964c2038a8c587ca Mon Sep 17 00:00:00 2001
From: Christopher Bate <cbate at nvidia.com>
Date: Wed, 21 Oct 2026 14:48:40 -0600
Subject: [PATCH] [MLIR][CMake] Fix LLVM_DEFINITIONS handling in standalone
 example

Split LLVM_DEFINITIONS into a CMake list before passing it to add_definitions(), and apply it before HandleLLVMOptions overwrites the variable.

Add comments explaining the compile and linker flag setup and how to scope HandleLLVMOptions around third-party dependencies.
---
 mlir/examples/standalone/CMakeLists.txt | 12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/mlir/examples/standalone/CMakeLists.txt b/mlir/examples/standalone/CMakeLists.txt
index 17d712f6a1064a..9b203af7467c06 100644
--- a/mlir/examples/standalone/CMakeLists.txt
+++ b/mlir/examples/standalone/CMakeLists.txt
@@ -22,9 +22,20 @@ if(CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   list(APPEND CMAKE_MODULE_PATH "${MLIR_CMAKE_DIR}")
   list(APPEND CMAKE_MODULE_PATH "${LLVM_CMAKE_DIR}")
 
+  # LLVM_DEFINITIONS is a space-separated string of command-line flags (e.g.
+  # "-D_GNU_SOURCE -D__STDC_CONSTANT_MACROS"), so split it into a CMake list
+  # before passing it to add_definitions(). Do this before including
+  # HandleLLVMOptions, which overwrites LLVM_DEFINITIONS in the current scope.
+  separate_arguments(LLVM_DEFINITIONS_LIST NATIVE_COMMAND ${LLVM_DEFINITIONS})
+  add_definitions(${LLVM_DEFINITIONS_LIST})
+
   include(TableGen)
   include(AddLLVM)
   include(AddMLIR)
+  # Configure C/C++ compiler and linker flags matching the LLVM/MLIR build.
+  # Note: If your project builds third-party C++ dependencies from source that
+  # do not depend on LLVM/MLIR, add them before including HandleLLVMOptions so
+  # they are not affected by LLVM-specific warning, assertion, or linker flags.
   include(HandleLLVMOptions)
 else()
   set(EXTERNAL_PROJECT_BUILD TRUE)
@@ -54,7 +65,6 @@ include_directories(${MLIR_INCLUDE_DIRS})
 include_directories(${STANDALONE_SOURCE_DIR}/include)
 include_directories(${STANDALONE_BINARY_DIR}/include)
 link_directories(${LLVM_BUILD_LIBRARY_DIR})
-add_definitions(${LLVM_DEFINITIONS})
 
 add_subdirectory(include)
 add_subdirectory(lib)