Pybind11 requires CMake of version 2.8.12 or newer. Because this is lower than 3.9, it sets the OLD behaviour of the policy 0069.
https://cmake.org/cmake/help/latest/policy/CMP0069.html#policy:CMP0069
With the OLD behaviour, LTO is not applied and this is warning displayed during the build:
-- Configuring done
CMake Warning (dev) at [...]/pybind11/tools/pybind11Tools.cmake:131 (add_library):
Policy CMP0069 is not set: INTERPROCEDURAL_OPTIMIZATION is enforced when
enabled. Run "cmake --help-policy CMP0069" for policy details. Use the
cmake_policy command to set the policy and suppress this warning.
INTERPROCEDURAL_OPTIMIZATION property will be ignored for target [...]
Pybind11 explicitly states in the documentation that it needs LTO to make good binary code so I think this is important.
I think this would be a good solution:
if(CMAKE_VERSION VERSION_GREATER_EQUAL 3.9)
cmake_policy(SET CMP0069 NEW)
endif()
Pybind11 requires CMake of version 2.8.12 or newer. Because this is lower than 3.9, it sets the OLD behaviour of the policy 0069.
https://cmake.org/cmake/help/latest/policy/CMP0069.html#policy:CMP0069
With the OLD behaviour, LTO is not applied and this is warning displayed during the build:
Pybind11 explicitly states in the documentation that it needs LTO to make good binary code so I think this is important.
I think this would be a good solution: