CMake/Modules/CheckCXXSymbolExists.cmake

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Simplify CMake per-source license notices Per-source copyright/license notice headers that spell out copyright holder names and years are hard to maintain and often out-of-date or plain wrong. Precise contributor information is already maintained automatically by the version control tool. Ultimately it is the receiver of a file who is responsible for determining its licensing status, and per-source notices are merely a convenience. Therefore it is simpler and more accurate for each source to have a generic notice of the license name and references to more detailed information on copyright holders and full license terms. Our `Copyright.txt` file now contains a list of Contributors whose names appeared source-level copyright notices. It also references version control history for more precise information. Therefore we no longer need to spell out the list of Contributors in each source file notice. Replace CMake per-source copyright/license notice headers with a short description of the license and links to `Copyright.txt` and online information available from "https://cmake.org/licensing". The online URL also handles cases of modules being copied out of our source into other projects, so we can drop our notices about replacing links with full license text. Run the `Utilities/Scripts/filter-notices.bash` script to perform the majority of the replacements mechanically. Manually fix up shebang lines and trailing newlines in a few files. Manually update the notices in a few files that the script does not handle.
2016-09-27 22:01:08 +03:00
# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
# file Copyright.txt or https://cmake.org/licensing for details.
#.rst:
# CheckCXXSymbolExists
# --------------------
#
# Check if a symbol exists as a function, variable, or macro in C++
#
# CHECK_CXX_SYMBOL_EXISTS(<symbol> <files> <variable>)
#
# 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.
# CHECK_CXX_SYMBOL_EXISTS() can be used to check in C++ files, as
# opposed to CHECK_SYMBOL_EXISTS(), which works only for C.
#
# 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
# as a function or variable then the symbol must also be available for
# linking. If the symbol is a type or enum value it will not be
# recognized (consider using CheckTypeSize or CheckCSourceCompiles).
#
# The following variables may be set before calling this macro to modify
# the way the check is run:
#
# ::
#
# CMAKE_REQUIRED_FLAGS = string of compile command line flags
# CMAKE_REQUIRED_DEFINITIONS = list of macros to define (-DFOO=bar)
# CMAKE_REQUIRED_INCLUDES = list of include directories
# CMAKE_REQUIRED_LIBRARIES = list of libraries to link
# CMAKE_REQUIRED_QUIET = execute quietly without messages
include(CheckSymbolExists)
macro(CHECK_CXX_SYMBOL_EXISTS SYMBOL FILES VARIABLE)
_CHECK_SYMBOL_EXISTS("${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckSymbolExists.cxx" "${SYMBOL}" "${FILES}" "${VARIABLE}" )
endmacro()