CMake: Expose Python LTO Control #980
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Before, LTO/IPO was default-enabled for the Python bindings. This can sometimes, e.g. on PPC64le with GCC 6.4.0 on Summit, cause problems in complex enough scenarios and fail to link. We now expose control via the standardized CMake variable `CMAKE_INTERPROCEDURAL_OPTIMIZATION`. This variable populates the `INTERPROCEDURAL_OPTIMIZATION` property of targets but only works really reliably with CMake 3.18+. We keep the default logic to use LTO, use the `pybind11::lto` target for older CMake but let the user deactivate the Python LTO by setting the `CMAKE_INTERPROCEDURAL_OPTIMIZATION` variable to false.
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Before, LTO/IPO was default-enabled for the Python bindings. This can sometimes, e.g. on PPC64le with GCC 6.4.0 on Summit, cause problems in complex enough scenarios and fail to link.
We now expose control via the standardized CMake variable
CMAKE_INTERPROCEDURAL_OPTIMIZATION. This variable populates theINTERPROCEDURAL_OPTIMIZATIONproperty of targets but only works really reliably with CMake 3.18+. We keep the default logic to use LTO, use thepybind11::ltotarget for older CMake but let the user deactivate the Python LTO by setting theCMAKE_INTERPROCEDURAL_OPTIMIZATIONvariable to false.Related to: pybind/pybind11#3006