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CheckFunctionExists: Document suggestion to use CheckSymbolExists instead.

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CheckFunctionExists has some severe limitations that are overcome by
CheckSymbolExists.  Document them and suggest the alternative.
This commit is contained in:
Stephen Sorley 2017-01-12 13:10:25 -05:00 committed by Brad King
parent 728820f3ea
commit 4ae2dcb1b9
1 changed files with 21 additions and 9 deletions
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30
Modules/CheckFunctionExists.cmake
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@ -5,18 +5,16 @@
# CheckFunctionExists
# -------------------
#
# Check if a C function can be linked
# Check if a C function can be linked::
#
# CHECK_FUNCTION_EXISTS(<function> <variable>)
# check_function_exists(<function> <variable>)
#
# Check that the <function> is provided by libraries on the system and
# 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.
# Check that the ``<function>`` is provided by libraries on the system and store
# the result in a ``<variable>``. ``<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:
# The following variables may be set before calling this macro to modify the
# way the check is run:
#
# ::
#
@ -25,6 +23,20 @@
# CMAKE_REQUIRED_INCLUDES = list of include directories
# CMAKE_REQUIRED_LIBRARIES = list of libraries to link
# CMAKE_REQUIRED_QUIET = execute quietly without messages
#
# .. note::
#
# Prefer using :Module:`CheckSymbolExists` instead of this module,
# for the following reasons:
#
# * ``check_function_exists()`` can't detect functions that are inlined
# in headers or specified as a macro.
#
# * ``check_function_exists()`` can't detect anything in the 32-bit
# versions of the Win32 API, because of a mismatch in calling conventions.
#
# * ``check_function_exists()`` only verifies linking, it does not verify
# that the function is declared in system headers.
macro(CHECK_FUNCTION_EXISTS FUNCTION VARIABLE)
if(NOT DEFINED "${VARIABLE}" OR "x${${VARIABLE}}" STREQUAL "x${VARIABLE}")