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# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
# file LICENSE.rst or https://cmake.org/licensing for details.
#[=======================================================================[.rst:
CheckPIESupported
-----------------
.. versionadded:: 3.14
This module provides the ``check_pie_supported()`` function to check whether the
linker supports Position Independent Code (PIE) or No Position Independent Code
(NO_PIE) for executables.
When setting the :prop_tgt:`POSITION_INDEPENDENT_CODE` target property,
PIC-related compile and link options are added when building library objects,
and PIE-related compile options are added when building objects of executable
targets, regardless of this module. Use this module to ensure that the
``POSITION_INDEPENDENT_CODE`` target property for executables is also honored at
link time.
.. command:: check_pie_supported
.. code-block:: cmake
check_pie_supported([OUTPUT_VARIABLE <output>]
[LANGUAGES <lang>...])
Options are:
``OUTPUT_VARIABLE <output>``
Set ``<output>`` variable with details about any error. If the check is
bypassed because it uses cached results from a previous call, the output
will be empty even if errors were present in the previous call.
``LANGUAGES <lang>...``
Check the linkers used for each of the specified languages.
If this option is not provided, the command checks all enabled languages.
``C``, ``CXX``, ``Fortran`` are supported.
.. versionadded:: 3.23
``OBJC``, ``OBJCXX``, ``CUDA``, and ``HIP`` are supported.
.. note::
To use ``check_pie_supported()``, policy :policy:`CMP0083` must be set to
``NEW``; otherwise, a fatal error will occur.
Variables
^^^^^^^^^
For each language checked, the ``check_pie_supported()`` function defines two
boolean cache variables:
``CMAKE_<lang>_LINK_PIE_SUPPORTED``
Set to true if ``PIE`` is supported by the linker and false otherwise.
``CMAKE_<lang>_LINK_NO_PIE_SUPPORTED``
Set to true if ``NO_PIE`` is supported by the linker and false otherwise.
Examples
^^^^^^^^
To enable PIE on an executable target at link time as well, include this module
and call ``check_pie_supported()`` before setting the
``POSITION_INDEPENDENT_CODE`` target property. This will determine whether the
linker for each checked language supports PIE-related link options. For
example:
.. code-block:: cmake
add_executable(foo ...)
include(CheckPIESupported)
check_pie_supported()
set_property(TARGET foo PROPERTY POSITION_INDEPENDENT_CODE TRUE)
Since not all linkers require or support PIE-related link options (for example,
``MSVC``), retrieving any error messages might be useful for logging purposes:
.. code-block:: cmake
add_executable(foo ...)
include(CheckPIESupported)
check_pie_supported(OUTPUT_VARIABLE output LANGUAGES C)
set_property(TARGET foo PROPERTY POSITION_INDEPENDENT_CODE TRUE)
if(NOT CMAKE_C_LINK_PIE_SUPPORTED)
message(WARNING "PIE is not supported at link time:\n${output}"
"PIE link options will not be passed to linker.")
endif()
Setting the ``POSITION_INDEPENDENT_CODE`` target property on an executable
without this module will set PIE-related compile options but not PIE-related
link options, which might not be sufficient in certain cases:
.. code-block:: cmake
add_executable(foo ...)
set_property(TARGET foo PROPERTY POSITION_INDEPENDENT_CODE TRUE)
#]=======================================================================]
include (Internal/CheckLinkerFlag)
function (check_pie_supported)
cmake_policy(GET CMP0083 cmp0083)
if (NOT cmp0083)
message(FATAL_ERROR "check_pie_supported: Policy CMP0083 is not set")
endif()
if(cmp0083 STREQUAL "OLD")
message(FATAL_ERROR "check_pie_supported: Policy CMP0083 set to OLD")
endif()
set(optional)
set(one OUTPUT_VARIABLE)
set(multiple LANGUAGES)
cmake_parse_arguments(CHECK_PIE "${optional}" "${one}" "${multiple}" "${ARGN}")
if(CHECK_PIE_UNPARSED_ARGUMENTS)
message(FATAL_ERROR "check_pie_supported: Unparsed arguments: ${CHECK_PIE_UNPARSED_ARGUMENTS}")
endif()
if (CHECK_PIE_LANGUAGES)
set (unsupported_languages "${CHECK_PIE_LANGUAGES}")
list (REMOVE_ITEM unsupported_languages "C" "CXX" "OBJC" "OBJCXX" "Fortran" "CUDA" "HIP")
if(unsupported_languages)
message(FATAL_ERROR "check_pie_supported: language(s) '${unsupported_languages}' not supported")
endif()
else()
# User did not set any languages, use defaults
get_property (enabled_languages GLOBAL PROPERTY ENABLED_LANGUAGES)
if (NOT enabled_languages)
return()
endif()
list (FILTER enabled_languages INCLUDE REGEX "^(C|CXX|OBJC|OBJCXX|Fortran|CUDA|HIP)$")
if (NOT enabled_languages)
return()
endif()
set (CHECK_PIE_LANGUAGES ${enabled_languages})
endif()
set(CMAKE_REQUIRED_QUIET TRUE)
set (outputs)
# Isolate the checks below from the project's PIC selection.
unset(CMAKE_POSITION_INDEPENDENT_CODE)
foreach(lang IN LISTS CHECK_PIE_LANGUAGES)
if(_CMAKE_${lang}_PIE_MAY_BE_SUPPORTED_BY_LINKER)
if(NOT DEFINED CMAKE_${lang}_LINK_PIE_SUPPORTED)
# ensure PIE compile flags are also used
list(JOIN CMAKE_${lang}_COMPILE_OPTIONS_PIE " " CMAKE_REQUIRED_FLAGS)
cmake_check_linker_flag(${lang}
"${CMAKE_${lang}_LINK_OPTIONS_PIE}"
CMAKE_${lang}_LINK_PIE_SUPPORTED
OUTPUT_VARIABLE output)
if (NOT CMAKE_${lang}_LINK_PIE_SUPPORTED)
string (APPEND outputs "PIE (${lang}): ${output}\n")
endif()
unset(CMAKE_REQUIRED_FLAGS)
endif()
if(NOT DEFINED CMAKE_${lang}_LINK_NO_PIE_SUPPORTED)
cmake_check_linker_flag(${lang}
"${CMAKE_${lang}_LINK_OPTIONS_NO_PIE}"
CMAKE_${lang}_LINK_NO_PIE_SUPPORTED
OUTPUT_VARIABLE output)
if (NOT CMAKE_${lang}_LINK_NO_PIE_SUPPORTED)
string (APPEND outputs "NO_PIE (${lang}): ${output}\n")
endif()
endif()
else()
# no support at link time. Set cache variables to NO
set(CMAKE_${lang}_LINK_PIE_SUPPORTED NO CACHE INTERNAL "PIE (${lang})")
set(CMAKE_${lang}_LINK_NO_PIE_SUPPORTED NO CACHE INTERNAL "NO_PIE (${lang})")
string (APPEND outputs "PIE and NO_PIE are not supported by linker for ${lang}\n")
endif()
endforeach()
if (CHECK_PIE_OUTPUT_VARIABLE)
set (${CHECK_PIE_OUTPUT_VARIABLE} "${outputs}" PARENT_SCOPE)
endif()
endfunction()
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