CMake/Help/command/try_compile.rst

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try_compile
-----------
Try building some code.
::
try_compile(RESULT_VAR <bindir> <srcdir>
<projectName> [targetName] [CMAKE_FLAGS flags...]
[OUTPUT_VARIABLE <var>])
Try building a project. In this form, srcdir should contain a
complete CMake project with a CMakeLists.txt file and all sources.
The bindir and srcdir will not be deleted after this command is run.
Specify targetName to build a specific target instead of the 'all' or
'ALL_BUILD' target.
::
try_compile(RESULT_VAR <bindir> <srcfile|SOURCES srcfile...>
[CMAKE_FLAGS flags...]
[COMPILE_DEFINITIONS flags...]
[LINK_LIBRARIES libs...]
[OUTPUT_VARIABLE <var>]
[COPY_FILE <fileName> [COPY_FILE_ERROR <var>]])
Try building an executable from one or more source files. In this
form the user need only supply one or more source files that include a
definition for 'main'. CMake will create a CMakeLists.txt file to
build the source(s) as an executable. Specify COPY_FILE to get a copy
of the linked executable at the given fileName and optionally
COPY_FILE_ERROR to capture any error.
In this version all files in bindir/CMakeFiles/CMakeTmp will be
cleaned automatically. For debugging, --debug-trycompile can be
passed to cmake to avoid this clean. However, multiple sequential
try_compile operations reuse this single output directory. If you use
--debug-trycompile, you can only debug one try_compile call at a time.
The recommended procedure is to protect all try_compile calls in your
project by ``if(NOT DEFINED RESULT_VAR)`` logic, configure with cmake
all the way through once, then delete the cache entry associated with
the try_compile call of interest, and then re-run cmake again with
--debug-trycompile.
Some extra flags that can be included are, INCLUDE_DIRECTORIES,
LINK_DIRECTORIES, and LINK_LIBRARIES. COMPILE_DEFINITIONS are
-Ddefinition that will be passed to the compile line.
The srcfile signature also accepts a LINK_LIBRARIES argument which may
contain a list of libraries or IMPORTED targets which will be linked
to in the generated project. If LINK_LIBRARIES is specified as a
parameter to try_compile, then any LINK_LIBRARIES passed as
CMAKE_FLAGS will be ignored.
try_compile creates a CMakeList.txt file on the fly that looks like
this:
::
add_definitions( <expanded COMPILE_DEFINITIONS from calling cmake>)
include_directories(${INCLUDE_DIRECTORIES})
link_directories(${LINK_DIRECTORIES})
add_executable(cmTryCompileExec sources)
target_link_libraries(cmTryCompileExec ${LINK_LIBRARIES})
In both versions of the command, if OUTPUT_VARIABLE is specified, then
the output from the build process is stored in the given variable.
The success or failure of the try_compile, i.e. TRUE or FALSE
respectively, is returned in RESULT_VAR. CMAKE_FLAGS can be used to
pass -DVAR:TYPE=VALUE flags to the cmake that is run during the build.
Set variable CMAKE_TRY_COMPILE_CONFIGURATION to choose a build
configuration.