| target_precompile_headers |
| ------------------------- |
| |
| Add a list of header files to precompile. |
| |
| .. code-block:: cmake |
| |
| target_precompile_headers(<target> |
| <INTERFACE|PUBLIC|PRIVATE> [header1...] |
| [<INTERFACE|PUBLIC|PRIVATE> [header2...] ...]) |
| |
| target_precompile_headers(<target> REUSE_FROM <other_target>) |
| |
| Adds header files to :prop_tgt:`PRECOMPILE_HEADERS` or |
| :prop_tgt:`INTERFACE_PRECOMPILE_HEADERS` target properties. |
| |
| The second signature will reuse an already precompiled header file artefact |
| from another target. This is done by setting the |
| :prop_tgt:`PRECOMPILE_HEADERS_REUSE_FROM` to ``<other_target>`` value. |
| The ``<other_target>`` will become a dependency of ``<target>``. |
| |
| .. note:: |
| |
| The second signature will require the same set of compiler options, |
| compiler flags, compiler definitions for both ``<target>``, and |
| ``<other_target>``. Compilers (e.g. GCC) will issue a warning if the |
| precompiled header file cannot be used (``-Winvalid-pch``). |
| |
| Precompiling header files can speed up compilation by creating a partially |
| processed version of some header files, and then using that version during |
| compilations rather than repeatedly parsing the original headers. |
| |
| The named ``<target>`` must have been created by a command such as |
| :command:`add_executable` or :command:`add_library` and must not be an |
| :ref:`ALIAS target <Alias Targets>`. |
| |
| The ``INTERFACE``, ``PUBLIC`` and ``PRIVATE`` keywords are required to |
| specify the scope of the following arguments. ``PRIVATE`` and ``PUBLIC`` |
| items will populate the :prop_tgt:`PRECOMPILE_HEADERS` property of |
| ``<target>``. ``PUBLIC`` and ``INTERFACE`` items will populate the |
| :prop_tgt:`INTERFACE_PRECOMPILE_HEADERS` property of ``<target>``. |
| (:ref:`IMPORTED targets <Imported Targets>` only support ``INTERFACE`` items.) |
| Repeated calls for the same ``<target>`` append items in the order called. |
| |
| Arguments to ``target_precompile_headers`` may use "generator expressions" |
| with the syntax ``$<...>``. |
| See the :manual:`cmake-generator-expressions(7)` manual for available |
| expressions. See the :manual:`cmake-compile-features(7)` manual for |
| information on compile features and a list of supported compilers. |
| |
| Usage |
| ^^^^^ |
| |
| .. code-block:: cmake |
| |
| target_precompile_headers(<target> |
| PUBLIC |
| project_header.h |
| PRIVATE |
| [["other_header.h"]] |
| <unordered_map> |
| ) |
| |
| The list of header files is used to generate a header file named |
| ``cmake_pch.h|xx`` which is used to generate the precompiled header file |
| (``.pch``, ``.gch``, ``.pchi``) artifact. The ``cmake_pch.h|xx`` header |
| file will be force included (``-include`` for GCC, ``/FI`` for MSVC) to |
| all source files, so sources do not need to have ``#include "pch.h"``. |
| |
| Header file names specified with angle brackets (e.g. ``<unordered_map>``) or |
| explicit double quotes (escaped for the :manual:`cmake-language(7)`, |
| e.g. ``[["other_header.h"]]``) will be treated as is, and include directories |
| must be available for the compiler to find them. Other header file names |
| (e.g. ``project_header.h``) are interpreted as being relative to the current |
| source directory (e.g. :variable:`CMAKE_CURRENT_SOURCE_DIR`) and will be |
| included by absolute path. |
| |
| See Also |
| ^^^^^^^^ |
| |
| For disabling precompile headers for specific targets there is the |
| property :prop_tgt:`DISABLE_PRECOMPILE_HEADERS`. |
| |
| For skipping certain source files there is the source file property |
| :prop_sf:`SKIP_PRECOMPILE_HEADERS`. |