add new CMake option `ABSL_USE_SYSTEM_INCLUDES`
When using Abseil as a dependency with CMake, files that include Abseil headers and have incompatible warning settings can emit compiler warnings. CMake allows you to mark include directories as `SYSTEM` includes, which causes compilers to ignore warnings from those headers.
This adds the new option `ABSL_USE_SYSTEM_INCLUDES`, which makes Abseil's include directories be marked with `SYSTEM`.
diff --git a/CMake/AbseilHelpers.cmake b/CMake/AbseilHelpers.cmake
index f81d57c..96d815d 100644
--- a/CMake/AbseilHelpers.cmake
+++ b/CMake/AbseilHelpers.cmake
@@ -26,6 +26,12 @@
set(ABSL_IDE_FOLDER Abseil)
endif()
+if(ABSL_USE_SYSTEM_INCLUDES)
+ set(ABSL_INTERNAL_INCLUDE_WARNING_GUARD SYSTEM)
+else()
+ set(ABSL_INTERNAL_INCLUDE_WARNING_GUARD "")
+endif()
+
# absl_cc_library()
#
# CMake function to imitate Bazel's cc_library rule.
@@ -242,7 +248,7 @@
# unconditionally.
set_property(TARGET ${_NAME} PROPERTY LINKER_LANGUAGE "CXX")
- target_include_directories(${_NAME}
+ target_include_directories(${_NAME} ${ABSL_INTERNAL_INCLUDE_WARNING_GUARD}
PUBLIC
"$<BUILD_INTERFACE:${ABSL_COMMON_INCLUDE_DIRS}>"
$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
@@ -290,7 +296,7 @@
else()
# Generating header-only library
add_library(${_NAME} INTERFACE)
- target_include_directories(${_NAME}
+ target_include_directories(${_NAME} ${ABSL_INTERNAL_INCLUDE_WARNING_GUARD}
INTERFACE
"$<BUILD_INTERFACE:${ABSL_COMMON_INCLUDE_DIRS}>"
$<INSTALL_INTERFACE:${CMAKE_INSTALL_INCLUDEDIR}>
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 10acf3b..6f96c28 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -70,6 +70,10 @@
message(WARNING "A future Abseil release will default ABSL_PROPAGATE_CXX_STD to ON for CMake 3.8 and up. We recommend enabling this option to ensure your project still builds correctly.")
endif()
+option(ABSL_USE_SYSTEM_INCLUDES
+ "Mark C++ include directories with `SYSTEM` to prevent warnings from headers when using Abseil with incompatible warning flags"
+ OFF)
+
list(APPEND CMAKE_MODULE_PATH
${CMAKE_CURRENT_LIST_DIR}/CMake
${CMAKE_CURRENT_LIST_DIR}/absl/copts
