I'm trying to build Ceres 1.13.0 for iOS 10+ using Xcode 9.2 (9C40b) and CMake 3.11.0-rc3. It seems CMake doesn't recognize the clang version provided by Xcode 9. Is that what's going on? Doesn't seem like it, since an older version of Ceres used to build just fine.
This question seems to suggest CMake doesn't support AppleClang, which seems ludicrous to me. A different team here builds a huge chunk of our code using CMake on macOS with only the Xcode-provided clang.
I also tried modifying the Ceres iOS.cmake file to set the CMP0025 policy as suggested by that SO answer, but it made no difference.
Update
I've noticed something. When CMake works for other builds, it properly identifies the compiler as AppleClang 9.0.0.9000039. When it fails, you can see the message below (it calls it "Clang"). In both cases, it identifies the CXX compiler at /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++. The output below shows the case where it fails to identify the compiler
$ cmake $CERES_DIR -DCMAKE_TOOLCHAIN_FILE=$CERES_DIR/cmake/iOS.cmake -DCXX11=ON -DLAPACK=OFF -DEIGEN_INCLUDE_DIR=$EIGEN_INCLUDE_DIR -DIOS_PLATFORM=OS -DCMAKE_BUILD_TYPE=Release -DCMAKE_INSTALL_PREFIX=../
-- Building with Xcode version: 9.2
-- Configuring iOS build for platform: OS, architecture(s): arm64
-- Using C compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang
-- Using CXX compiler: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/clang++
-- Using libtool: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/libtool
-- Building for minimum iOS version: 11.2 (SDK version: 11.2)
-- Detected Ceres version: 1.13.0 from /Users/me/Projects/Clients/MyCompany/repo/thirdparty/ceres-solver-1.13.0/include/ceres/version.h
-- Building Ceres for iOS platform: OS
-- Building for iOS: Forcing use of miniglog instead of glog.
-- Building for iOS: SuiteSparse, CXSparse, LAPACK, gflags, and OpenMP are not available.
-- Building for iOS: Will not build examples.
-- No preference for use of exported Eigen CMake configuration set, and no hints for include directory provided. Defaulting to preferring an installed/exported Eigen CMake configuration if available.
-- Found installed version of Eigen: /usr/local/share/eigen3/cmake
-- Found Eigen version 3.3.4: /usr/local/include/eigen3
===============================================================
Disabling the use of Eigen as a sparse linear algebra library.
This does not affect the covariance estimation algorithm
which can still use the EIGEN_SPARSE_QR algorithm.
===============================================================
-- Building without LAPACK.
-- Building without SuiteSparse.
-- Building without CXSparse.
===============================================================
Compiling without any sparse library: SuiteSparse, CXSparse
& Eigen (Sparse) are all disabled or unavailable. No sparse
linear solvers (SPARSE_NORMAL_CHOLESKY & SPARSE_SCHUR)
will be available when Ceres is used.
===============================================================
-- Google Flags disabled; no tests or tools will be built!
-- Compiling minimal glog substitute into Ceres.
-- Using minimal glog substitute (include): internal/ceres/miniglog
-- Max log level for minimal glog substitute: 2
-- Building without OpenMP (disabling multithreading).
-- Looking for C++ include unordered_map
-- Looking for C++ include unordered_map - found
-- Performing Test HAVE_UNORDERED_MAP_IN_STD_NAMESPACE
-- Performing Test HAVE_UNORDERED_MAP_IN_STD_NAMESPACE - Success
-- Found unordered_map/set in std namespace.
-- Looking for C++ include memory
-- Looking for C++ include memory - found
-- Performing Test HAVE_SHARED_PTR_IN_STD_NAMESPACE
-- Performing Test HAVE_SHARED_PTR_IN_STD_NAMESPACE - Success
-- Found shared_ptr in std namespace using <memory> header.
==============================================================
Compiling Ceres using C++11. This will result in a version
of Ceres that will require the use of C++11 in client code.
==============================================================
-- Building Ceres as a static library.
-- Enabling CERES_NO_LAPACK in Ceres config.h
-- Enabling CERES_NO_SUITESPARSE in Ceres config.h
-- Enabling CERES_NO_CXSPARSE in Ceres config.h
-- Enabling CERES_USE_CXX11 in Ceres config.h
-- Enabling CERES_NO_THREADS in Ceres config.h
-- Enabling CERES_STD_UNORDERED_MAP in Ceres config.h
CMake Error at cmake/AddCeresCXX11RequirementsToTarget.cmake:70 (target_compile_features):
target_compile_features no known features for CXX compiler
"Clang"
version 9.0.0.9000039.
Call Stack (most recent call first):
internal/ceres/CMakeLists.txt:223 (add_ceres_cxx11_requirements_to_target)
-- Do not build any example.
-- Configuring incomplete, errors occurred!
See also "/Users/me/Projects/Clients/MyCompany/repo/iOS/lib/ceres/build/CMakeFiles/CMakeOutput.log".
Xcode version:
$ /usr/bin/clang --version
Apple LLVM version 9.0.0 (clang-900.0.39.2)
Target: x86_64-apple-darwin17.4.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
Guidance is much appreciated.
