Use target_compile_features() to specify C++11 requirement if available.
- Use target_compile_features() to specify the C++11 dependency for
Ceres if the CXX11 option is enabled and the current CMake version
supports it (>= 3.1). Otherwise fall back onto our existing
target_compile_options() solution if available.
- We prefer the use of target_compile_features() if available as it more
gracefully handles ‘upgrading’ of the C++ standard in client projects
that depend upon Ceres, e.g. if the client requires C++14. The
current solution may fail to produce the expected result in this case
as raised in
https://github.com/ceres-solver/ceres-solver/issues/273.
Change-Id: Ib3cff8d4b9fe93fa6d6b376b4dd53923bb1c4ecc
diff --git a/CMakeLists.txt b/CMakeLists.txt
index a782c34..63f5e10 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -507,7 +507,12 @@
message(" of Ceres that will require the use of C++11 in client code.")
message(" ==============================================================")
list(APPEND CERES_COMPILE_OPTIONS CERES_USE_CXX11)
- if (COMPILER_HAS_CXX11_FLAG)
+ if (COMPILER_HAS_CXX11_FLAG AND
+ CMAKE_VERSION VERSION_LESS "2.8.12")
+ # For CMake versions > 2.8.12, the C++11 dependency is rolled into the
+ # Ceres target, and all dependent targets, but for older versions of CMake
+ # the flag must be specified explicitly both for Ceres and the
+ # examples/tests.
set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -std=c++11")
endif()
endif()
diff --git a/cmake/AddCeresCXX11RequirementsToTarget.cmake b/cmake/AddCeresCXX11RequirementsToTarget.cmake
new file mode 100644
index 0000000..107eb58
--- /dev/null
+++ b/cmake/AddCeresCXX11RequirementsToTarget.cmake
@@ -0,0 +1,84 @@
+# Ceres Solver - A fast non-linear least squares minimizer
+# Copyright 2017 Google Inc. All rights reserved.
+# http://ceres-solver.org/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice,
+# this list of conditions and the following disclaimer.
+# * Redistributions in binary form must reproduce the above copyright notice,
+# this list of conditions and the following disclaimer in the documentation
+# and/or other materials provided with the distribution.
+# * Neither the name of Google Inc. nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+# Author: alexs.mac@gmail.com (Alex Stewart)
+
+# Adds Ceres' C++11 requirements to a target such that they are exported when
+# the target is exported (if the version of CMake supports it).
+#
+# add_ceres_cxx11_requirements_to_target( [target1 [target2 [...]]] )
+function(add_ceres_cxx11_requirements_to_target)
+ include(CheckCXXCompilerFlag)
+ check_cxx_compiler_flag("-std=c++11" COMPILER_HAS_CXX11_FLAG)
+
+ foreach(TARGET ${ARGN})
+ if (NOT TARGET ${TARGET})
+ message(FATAL_ERROR "Specified target to append Ceres C++11 requirements "
+ "to: ${TARGET} is not a declared CMake target.")
+ endif()
+
+ if (COMPILER_HAS_CXX11_FLAG)
+ # IMPORTANT: It is not sufficient to specify the
+ # CXX_STANDARD/CXX_STANDARD_REQUIRED target properties
+ # as these target properties are NOT exported.
+ if (CMAKE_VERSION VERSION_LESS "2.8.12")
+ # CMake version < 2.8.12 does not support target_compile_options(), warn
+ # user that they will have to add compile flags to their own projects
+ # manually.
+ message(WARNING "-- Warning: Detected CMake version: ${CMAKE_VERSION} "
+ "< 2.8.12, which is the minimum required for compile options to be "
+ "included in an exported CMake target and the detected. compiler "
+ "requires -std=c++11. The client is responsible for adding "
+ "-std=c++11 when linking against: ${TARGET}.")
+ elseif (COMMAND target_compile_features)
+ # CMake >= 3.1, use new target_compile_features() to specify Ceres'
+ # C++11 requirements as used in the public API. This assumes that
+ # C++11 STL features are available if the specified features are
+ # available. We do not use the cxx_std_11 feature to specify this as
+ # this did not come in until CMake 3.8.
+ #
+ # The reason to prefer using target_compile_features() if it exists is
+ # that this handles 'upgrading' of the C++ standard required more
+ # gracefully, e.g. if a client of Ceres requires C++14, but Ceres was
+ # compiled against C++11 then target_compile_options() may not work as
+ # expected.
+ target_compile_features(
+ ${TARGET} PUBLIC cxx_alignas cxx_alignof cxx_constexpr)
+ else()
+ # CMake version >= 2.8.12 && < 3.1 supports target_compile_options()
+ # but not target_compile_features(). For these intermediary versions,
+ # we use target_compile_options() to manually specify the C++11 flag and
+ # export it for client targets that depend on the target iff they are
+ # NOT compiling for C. We check for not C, rather than C++ as
+ # LINKER_LANGUAGE is often NOTFOUND and then uses the default (C++).
+ target_compile_options(${TARGET} PUBLIC
+ $<$<NOT:$<STREQUAL:$<TARGET_PROPERTY:LINKER_LANGUAGE>,C>>:-std=c++11>)
+ endif()
+ endif()
+ endforeach()
+endfunction()
diff --git a/internal/ceres/CMakeLists.txt b/internal/ceres/CMakeLists.txt
index 5b6e99c..b113de5 100644
--- a/internal/ceres/CMakeLists.txt
+++ b/internal/ceres/CMakeLists.txt
@@ -214,29 +214,9 @@
endif()
endif()
-if (CMAKE_VERSION VERSION_LESS "2.8.12")
- # CMake version < 2.8.12 does not support target_compile_options(), warn
- # user that they will have to add compile flags to their own projects
- # manually if required.
- if (CXX11 AND COMPILER_HAS_CXX11_FLAG)
- message("-- Warning: Detected CMake version: ${CMAKE_VERSION} < 2.8.12, "
- "which is the minimum required for compile options to be included in an "
- "exported CMake target, but CERES_USE_CXX11 is enabled and the detected. "
- "compiler requires -std=c++11. The client is responsible for adding "
- "-std=c++11 when using Ceres.")
- endif()
-else()
- # CMake version >= 2.8.12 supports target_compile_options().
- if (CXX11 AND COMPILER_HAS_CXX11_FLAG)
- # If Ceres is compiled using C++11, and the compiler requires -std=c++11
- # to be set, then ensure that this requirement is rolled into the exported
- # CMake target, such that client code which uses Ceres will inherit it (if
- # the CMake version supports it), iff they are NOT compiling for C. We
- # check for not C, rather than C++ as LINKER_LANGUAGE is often NOTFOUND and
- # then uses the default (C++).
- target_compile_options(ceres PUBLIC
- $<$<NOT:$<STREQUAL:$<TARGET_PROPERTY:LINKER_LANGUAGE>,C>>:-std=c++11>)
- endif()
+if (CXX11)
+ include(AddCeresCXX11RequirementsToTarget)
+ add_ceres_cxx11_requirements_to_target(ceres)
endif()
if (BUILD_SHARED_LIBS)
