Merge topic 'try_compile-lang-std'

f72ba42b try_compile: Add policy CMP0067 to honor language standards
45aa03b9 try_compile: Add options to specify language standards
3bb2051e try_compile: Stop processing when test build system fails to generate

5 files changed, 84 insertions, 1 deletions

diff --git a/Help/command/try_compile.rst b/Help/command/try_compile.rst
index 7830deb..cde3776 100644
--- a/Help/command/try_compile.rst
+++ b/Help/command/try_compile.rst
@@ -35,7 +35,11 @@ Try Compiling Source Files
               [COMPILE_DEFINITIONS <defs>...]
               [LINK_LIBRARIES <libs>...]
               [OUTPUT_VARIABLE <var>]
-              [COPY_FILE <fileName> [COPY_FILE_ERROR <var>]])
+              [COPY_FILE <fileName> [COPY_FILE_ERROR <var>]]
+              [<LANG>_STANDARD <std>]
+              [<LANG>_STANDARD_REQUIRED <bool>]
+              [<LANG>_EXTENSIONS <bool>]
+              )
 
 Try building an executable from one or more source files.  The success or
 failure of the ``try_compile``, i.e. ``TRUE`` or ``FALSE`` respectively, is
@@ -82,6 +86,18 @@ The options are:
 ``OUTPUT_VARIABLE <var>``
   Store the output from the build process the given variable.
 
+``<LANG>_STANDARD <std>``
+  Specify the :prop_tgt:`C_STANDARD` or :prop_tgt:`CXX_STANDARD`
+  target property of the generated project.
+
+``<LANG>_STANDARD_REQUIRED <bool>``
+  Specify the :prop_tgt:`C_STANDARD_REQUIRED` or
+  :prop_tgt:`CXX_STANDARD_REQUIRED` target property of the generated project.
+
+``<LANG>_EXTENSIONS <bool>``
+  Specify the :prop_tgt:`C_EXTENSIONS` or :prop_tgt:`CXX_EXTENSIONS`
+  target property of the generated project.
+
 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
@@ -119,3 +135,17 @@ the type of target used for the source file signature.
 Set the :variable:`CMAKE_TRY_COMPILE_PLATFORM_VARIABLES` variable to specify
 variables that must be propagated into the test project.  This variable is
 meant for use only in toolchain files.
+
+If :policy:`CMP0067` is set to ``NEW``, or any of the ``<LANG>_STANDARD``,
+``<LANG>_STANDARD_REQUIRED``, or ``<LANG>_EXTENSIONS`` options are used,
+then the language standard variables are honored:
+
+* :variable:`CMAKE_C_STANDARD`
+* :variable:`CMAKE_C_STANDARD_REQUIRED`
+* :variable:`CMAKE_C_EXTENSIONS`
+* :variable:`CMAKE_CXX_STANDARD`
+* :variable:`CMAKE_CXX_STANDARD_REQUIRED`
+* :variable:`CMAKE_CXX_EXTENSIONS`
+
+Their values are used to set the corresponding target properties in
+the generated project (unless overridden by an explicit option).
diff --git a/Help/manual/cmake-policies.7.rst b/Help/manual/cmake-policies.7.rst
index 0cfe983..3266958 100644
--- a/Help/manual/cmake-policies.7.rst
+++ b/Help/manual/cmake-policies.7.rst
@@ -51,6 +51,14 @@ The :variable:`CMAKE_MINIMUM_REQUIRED_VERSION` variable may also be used
 to determine whether to report an error on use of deprecated macros or
 functions.
 
+Policies Introduced by CMake 3.8
+================================
+
+.. toctree::
+   :maxdepth: 1
+
+   CMP0067: Honor language standard in try_compile() source-file signature. </policy/CMP0067>
+
 Policies Introduced by CMake 3.7
 ================================
 
diff --git a/Help/policy/CMP0067.rst b/Help/policy/CMP0067.rst
new file mode 100644
index 0000000..d52ba7f
--- /dev/null
+++ b/Help/policy/CMP0067.rst
@@ -0,0 +1,34 @@
+CMP0067
+-------
+
+Honor language standard in :command:`try_compile` source-file signature.
+
+The :command:`try_compile` source file signature is intended to allow
+callers to check whether they will be able to compile a given source file
+with the current toolchain.  In order to match compiler behavior, any
+language standard mode should match.  However, CMake 3.7 and below did not
+do this.  CMake 3.8 and above prefer to honor the language standard settings
+for ``C`` and ``CXX`` (C++) using the values of the variables:
+
+* :variable:`CMAKE_C_STANDARD`
+* :variable:`CMAKE_C_STANDARD_REQUIRED`
+* :variable:`CMAKE_C_EXTENSIONS`
+* :variable:`CMAKE_CXX_STANDARD`
+* :variable:`CMAKE_CXX_STANDARD_REQUIRED`
+* :variable:`CMAKE_CXX_EXTENSIONS`
+
+This policy provides compatibility for projects that do not expect
+the language standard settings to be used automatically.
+
+The ``OLD`` behavior of this policy is to ignore language standard
+setting variables when generating the ``try_compile`` test project.
+The ``NEW`` behavior of this policy is to honor language standard
+setting variables.
+
+This policy was introduced in CMake version 3.8.  Unlike most policies,
+CMake version |release| does *not* warn by default when this policy
+is not set and simply uses OLD behavior.  See documentation of the
+:variable:`CMAKE_POLICY_WARNING_CMP0067 <CMAKE_POLICY_WARNING_CMP<NNNN>>`
+variable to control the warning.
+
+.. include:: DEPRECATED.txt
diff --git a/Help/release/dev/try_compile-lang-std.rst b/Help/release/dev/try_compile-lang-std.rst
new file mode 100644
index 0000000..849cecc
--- /dev/null
+++ b/Help/release/dev/try_compile-lang-std.rst
@@ -0,0 +1,9 @@
+try_compile-lang-std
+--------------------
+
+* The :command:`try_compile` command source file signature gained new options
+  to specify the language standard to use in the generated test project.
+
+* The :command:`try_compile` command source file signature now honors
+  language standard variables like :variable:`CMAKE_CXX_STANDARD`.
+  See policy :policy:`CMP0067`.
diff --git a/Help/variable/CMAKE_POLICY_WARNING_CMPNNNN.rst b/Help/variable/CMAKE_POLICY_WARNING_CMPNNNN.rst
index 36cf75f..aa23b65 100644
--- a/Help/variable/CMAKE_POLICY_WARNING_CMPNNNN.rst
+++ b/Help/variable/CMAKE_POLICY_WARNING_CMPNNNN.rst
@@ -17,6 +17,8 @@ warn by default:
   policy :policy:`CMP0065`.
 * ``CMAKE_POLICY_WARNING_CMP0066`` controls the warning for
   policy :policy:`CMP0066`.
+* ``CMAKE_POLICY_WARNING_CMP0067`` controls the warning for
+  policy :policy:`CMP0067`.
 
 This variable should not be set by a project in CMake code.  Project
 developers running CMake may set this variable in their cache to