Help: Check*Runs requires exit code 0 for success

Explicitly state this requirement to avoid ambiguity in what is
'success' of a program.

Modules/CheckCSourceRuns.cmake

@@ -19,9 +19,9 @@ subsequently be run.
   function.
 
   The result is stored in the internal cache variable specified by
-  ``<resultVar>``. Success of build and run is indicated by boolean ``true``.
+  ``<resultVar>``. If the code builds and runs with exit code ``0``, success is
-  Failure to build or run is indicated by boolean ``false`` such as an empty
+  indicated by boolean ``true``. Failure to build or run is indicated by boolean
-  string or an error message.
+  ``false``, such as an empty string or an error message.
 
   See also :command:`check_source_runs` for a more general command syntax.
 

Modules/CheckCXXSourceRuns.cmake

@@ -19,9 +19,9 @@ subsequently be run.
   function.
 
   The result is stored in the internal cache variable specified by
-  ``<resultVar>``. Success of build and run is indicated by boolean ``true``.
+  ``<resultVar>``. If the code builds and runs with exit code ``0``, success is
-  Failure to build or run is indicated by boolean ``false`` such as an empty
+  indicated by boolean ``true``. Failure to build or run is indicated by boolean
-  string or an error message.
+  ``false``, such as an empty string or an error message.
 
   See also :command:`check_source_runs` for a more general command syntax.
 

Modules/CheckFortranSourceRuns.cmake

@@ -21,9 +21,9 @@ subsequently be run.
   executable, and then run. The ``<code>`` must contain a Fortran ``program``.
 
   The result is stored in the internal cache variable specified by
-  ``<resultVar>``. Success of build and run is indicated by boolean ``true``.
+  ``<resultVar>``. If the code builds and runs with exit code ``0``, success is
-  Failure to build or run is indicated by boolean ``false`` such as an empty
+  indicated by boolean ``true``. Failure to build or run is indicated by boolean
-  string or an error message.
+  ``false``, such as an empty string or an error message.
 
   .. code-block:: cmake
 

Modules/CheckOBJCSourceRuns.cmake

@@ -21,9 +21,9 @@ can subsequently be run.
   function.
 
   The result is stored in the internal cache variable specified by
-  ``<resultVar>``. Success of build and run is indicated by boolean ``true``.
+  ``<resultVar>``. If the code builds and runs with exit code ``0``, success is
-  Failure to build or run is indicated by boolean ``false`` such as an empty
+  indicated by boolean ``true``. Failure to build or run is indicated by boolean
-  string or an error message.
+  ``false``, such as an empty string or an error message.
 
   See also :command:`check_source_runs` for a more general command syntax.
 

Modules/CheckOBJCXXSourceRuns.cmake

@@ -21,9 +21,9 @@ and can subsequently be run.
   function.
 
   The result is stored in the internal cache variable specified by
-  ``<resultVar>``. Success of build and run is indicated by boolean ``true``.
+  ``<resultVar>``. If the code builds and runs with exit code ``0``, success is
-  Failure to build or run is indicated by boolean ``false`` such as an empty
+  indicated by boolean ``true``. Failure to build or run is indicated by boolean
-  string or an error message.
+  ``false``, such as an empty string or an error message.
 
   See also :command:`check_source_runs` for a more general command syntax.
 

Modules/CheckSourceRuns.cmake

@@ -23,9 +23,9 @@ subsequently be run.
   a ``main()`` function, or in Fortran a ``program``.
 
   The result is stored in the internal cache variable specified by
-  ``<resultVar>``. Success of build and run is indicated by boolean ``true``.
+  ``<resultVar>``. If the code builds and runs with exit code ``0``, success is
-  Failure to build or run is indicated by boolean ``false`` such as an empty
+  indicated by boolean ``true``. Failure to build or run is indicated by boolean
-  string or an error message.
+  ``false``, such as an empty string or an error message.
 
   By default, the test source file will be given a file extension that matches
   the requested language. The ``SRC_EXT`` option can be used to override this