1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
|
# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
# file LICENSE.rst or https://cmake.org/licensing for details.
#[=======================================================================[.rst:
CheckCompilerFlag
---------------------
.. versionadded:: 3.19
This module provides a command to check whether the compiler supports a given
flag.
Load this module in a CMake project with:
.. code-block:: cmake
include(CheckCompilerFlag)
Commands
^^^^^^^^
This module provides the following command:
.. command:: check_compiler_flag
Checks once whether the compiler supports a given flag:
.. code-block:: cmake
check_compiler_flag(<lang> <flag> <variable>)
This command checks once that the ``<flag>`` is accepted by the ``<lang>``
compiler without producing a diagnostic message. The result of the check
is stored in the internal cache variable specified by ``<variable>``.
The arguments are:
``<lang>``
The language of the compiler used for the check. Supported languages
are: ``C``, ``CXX``, ``CUDA``, ``Fortran``, ``HIP``, ``ISPC``, ``OBJC``,
and ``OBJCXX``, and ``Swift``.
.. versionadded:: 3.21
Support for ``HIP`` language.
.. versionadded:: 3.26
Support for ``Swift`` language.
``<flag>``
Compiler flag(s) to check. Multiple flags can be specified in one
argument as a string using a :ref:`semicolon-separated list
<CMake Language Lists>`.
``<variable>``
Variable name of an internal cache variable to store the result of the
check, with boolean true for success and boolean false for failure.
A successful result only indicates that the compiler did not report an
error when given the flag. Whether the flag has any effect, or the
intended one, is outside the scope of this module.
.. note::
Since the underlying :command:`try_compile` command also uses flags from
variables like :variable:`CMAKE_<LANG>_FLAGS`, unknown or unsupported
flags in those variables may result in a false negative for this check.
.. rubric:: Variables Affecting the Check
The following variables may be set before calling this command to modify
the way the check is run:
.. include:: /module/include/CMAKE_REQUIRED_FLAGS.rst
.. include:: /module/include/CMAKE_REQUIRED_DEFINITIONS.rst
.. include:: /module/include/CMAKE_REQUIRED_INCLUDES.rst
.. include:: /module/include/CMAKE_REQUIRED_LINK_OPTIONS.rst
.. include:: /module/include/CMAKE_REQUIRED_LIBRARIES.rst
.. include:: /module/include/CMAKE_REQUIRED_LINK_DIRECTORIES.rst
.. include:: /module/include/CMAKE_REQUIRED_QUIET.rst
.. include:: /module/include/CMAKE_TRY_COMPILE_TARGET_TYPE.rst
Examples
^^^^^^^^
The following example demonstrates how to use this module to check support
for the C compiler flag ``-fno-optimize-strlen``, which disables
optimizations related to the ``strlen()`` C function in GCC and Clang
compilers. The result of the check is stored in the internal cache
variable ``HAVE_FNO_OPTIMIZE_STRLEN``, and the flag is conditionally enabled
using the :command:`target_compile_options` command. The
:genex:`$<COMPILE_LANGUAGE:...> <COMPILE_LANGUAGE:languages>` generator
expression ensures that the flag is added only to ``C`` source files.
.. code-block:: cmake
include(CheckCompilerFlag)
check_compiler_flag(C -fno-optimize-strlen HAVE_FNO_OPTIMIZE_STRLEN)
if(HAVE_FNO_OPTIMIZE_STRLEN)
target_compile_options(
example
PRIVATE $<$<COMPILE_LANGUAGE:C>:-fno-optimize-strlen>
)
endif()
See Also
^^^^^^^^
* The :module:`CheckLinkerFlag` module to check whether a linker flag is
supported by the compiler.
#]=======================================================================]
include_guard(GLOBAL)
include(Internal/CheckCompilerFlag)
function(CHECK_COMPILER_FLAG _lang _flag _var)
cmake_check_compiler_flag(${_lang} "${_flag}" ${_var})
endfunction()
|
