CMP0154ΒΆ
New in version 3.28.
Generated files are private by default in targets using File Sets.
CMake 3.27 and below assume that any file generated as an output or byproduct
of add_custom_command()
or add_custom_target()
may be a
public header file meant for inclusion by dependents' source files. This
requires Ninja Generators to add conservative order-only dependencies
that prevent a target's source files from compiling before custom commands
from the target's dependencies are finished, even if those custom commands
only produce sources private to their own target.
File Sets, introduced by CMake 3.23, provide a way to express the
visibility of generated header files. CMake 3.28 and above prefer to
assume that, in targets using file sets, generated files are private to
their own target by default. Generated public headers must be specified
as members of a PUBLIC
(or INTERFACE
) FILE_SET
, typically of
type HEADERS
. With this information, Ninja Generators may omit
the above-mentioned conservative dependencies and produce more efficient
build graphs.
Additionally, if the custom command's output is a member of a file set of type
CXX_MODULES
, it will additionally not be required to exist before
compiling other sources in the same target. Since these files should not be
included at compile time directly, they may not be implicitly required to
exist for other compilation rules.
This policy provides compatibility for projects using file sets in targets with generated header files that have not been updated. Such projects should be updated to express generated public headers in a file set. For example:
add_custom_command(
OUTPUT ${CMAKE_CURRENT_BINARY_DIR}/foo.h
...
)
target_sources(foo
PUBLIC FILE_SET HEADERS
BASE_DIRS ${CMAKE_CURRENT_BINARY_DIR}
FILES ${CMAKE_CURRENT_BINARY_DIR}/foo.h
)
The OLD
behavior for this policy is to assume generated files are
public, even in targets using file sets, and for Ninja Generators
to produce conservative build graphs. The NEW
behavior for this
policy is to assume generated files are private in targets using file sets,
and for Ninja Generators to produce more efficient build graphs.
This policy was introduced in CMake version 3.28.
It may be set by cmake_policy()
or cmake_minimum_required()
.
If it is not set, CMake does not warn, and uses OLD
behavior.
Note
The OLD
behavior of a policy is
deprecated by definition
and may be removed in a future version of CMake.