Help: Document that the CHECK_* macros create cache variables

Otherwise callers may expect to be able to re-use result variables.

Modules/CheckCCompilerFlag.cmake

@@ -10,6 +10,7 @@
 #
 #   <flag> - the compiler flag
 #   <var>  - variable to store the result
+#            Will be created as an internal cache variable.
 #
 # This internally calls the check_c_source_compiles macro and sets
 # CMAKE_REQUIRED_DEFINITIONS to <flag>.  See help for

Modules/CheckCSourceCompiles.cmake

@@ -10,6 +10,7 @@
 #
 #   <code>       - source code to try to compile, must define 'main'
 #   <var>        - variable to store whether the source code compiled
+#                  Will be created as an internal cache variable.
 #   <fail-regex> - fail if test output matches this regex
 #
 # The following variables may be set before calling this macro to modify

Modules/CheckCSourceRuns.cmake

@@ -11,6 +11,7 @@
 #   <code>   - source code to try to compile
 #   <var>    - variable to store the result
 #              (1 for success, empty for failure)
+#              Will be created as an internal cache variable.
 #
 # The following variables may be set before calling this macro to modify
 # the way the check is run:

Modules/CheckCXXSourceCompiles.cmake

@@ -10,6 +10,7 @@
 #
 #   <code>       - source code to try to compile, must define 'main'
 #   <var>        - variable to store whether the source code compiled
+#                  Will be created as an internal cache variable.
 #   <fail-regex> - fail if test output matches this regex
 #
 # The following variables may be set before calling this macro to modify

Modules/CheckCXXSourceRuns.cmake

@@ -11,6 +11,7 @@
 #   <code>   - source code to try to compile
 #   <var>    - variable to store the result
 #              (1 for success, empty for failure)
+#              Will be created as an internal cache variable.
 #
 # The following variables may be set before calling this macro to modify
 # the way the check is run:

Modules/CheckFortranFunctionExists.cmake

@@ -10,6 +10,7 @@
 #
 #   FUNCTION - the name of the Fortran function
 #   VARIABLE - variable to store the result
+#              Will be created as an internal cache variable.
 #
 #
 #

Modules/CheckFortranSourceCompiles.cmake

@@ -12,6 +12,7 @@
 #   Source code to try to compile.  It must define a PROGRAM entry point.
 # ``<var>``
 #   Variable to store whether the source code compiled.
+#   Will be created as an internal cache variable.
 # ``<fail-regex>``
 #   Fail if test output matches this regex.
 #

Modules/CheckFunctionExists.cmake

@@ -10,6 +10,7 @@
 # store the result in a <variable>.  This does not verify that any
 # system header file declares the function, only that it can be found at
 # link time (consider using CheckSymbolExists).
+# <variable> will be created as an internal cache variable.
 #
 # The following variables may be set before calling this macro to modify
 # the way the check is run:

Modules/CheckIncludeFile.cmake

@@ -10,6 +10,7 @@
 #
 #   INCLUDE  - name of include file
 #   VARIABLE - variable to return result
+#              Will be created as an internal cache variable.
 #
 #
 #

Modules/CheckIncludeFileCXX.cmake

@@ -14,6 +14,7 @@
 #
 #   INCLUDE  - name of include file
 #   VARIABLE - variable to return result
+#              Will be created as an internal cache variable.
 #
 #
 #

Modules/CheckIncludeFiles.cmake

@@ -12,6 +12,7 @@
 #
 #   INCLUDE  - list of files to include
 #   VARIABLE - variable to return result
+#              Will be created as an internal cache variable.
 #
 #
 #

Modules/CheckLibraryExists.cmake

@@ -12,6 +12,7 @@
 #   FUNCTION - the name of the function
 #   LOCATION - location where the library should be found
 #   VARIABLE - variable to store the result
+#              Will be created as an internal cache variable.
 #
 #
 #

Modules/CheckPrototypeDefinition.cmake

@@ -13,6 +13,7 @@
 #   RETURN - The return value of the function.
 #   HEADER - The header files required.
 #   VARIABLE - The variable to store the result.
+#              Will be created as an internal cache variable.
 #
 # Example:
 #

Modules/CheckSymbolExists.cmake

@@ -9,6 +9,7 @@
 # Check that the <symbol> is available after including given header
 # <files> and store the result in a <variable>.  Specify the list of
 # files in one argument as a semicolon-separated list.
+# <variable> will be created as an internal cache variable.
 #
 # If the header files define the symbol as a macro it is considered
 # available and assumed to work.  If the header files declare the symbol

Modules/CheckTypeSize.cmake

@@ -19,6 +19,9 @@
 #    "0"    = type has arch-dependent size (see below)
 #    ""     = type does not exist
 #
+# Both ``HAVE_${VARIABLE}`` and ``${VARIABLE}`` will be created as internal
+# cache variables.
+#
 # Furthermore, the variable "${VARIABLE}_CODE" holds C preprocessor code
 # to define the macro "${VARIABLE}" to the size of the type, or leave
 # the macro undefined if the type does not exist.

Modules/CheckVariableExists.cmake

@@ -14,7 +14,7 @@
 #
 #   VAR      - the name of the variable
 #   VARIABLE - variable to store the result
-#
+#              Will be created as an internal cache variable.
 #
 #
 # This macro is only for C variables.