CMake/Modules/CheckSymbolExists.cmake
Brad King 86578eccf2 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names and years are hard to maintain and often out-of-date or plain wrong.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 15:14:44 -04:00

108 lines
4.3 KiB
CMake

# Distributed under the OSI-approved BSD 3-Clause License. See accompanying
# file Copyright.txt or https://cmake.org/licensing for details.
#.rst:
# CheckSymbolExists
# -----------------
#
# Check if a symbol exists as a function, variable, or macro
#
# CHECK_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.
# <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
# 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). If
# the check needs to be done in C++, consider using
# CHECK_CXX_SYMBOL_EXISTS(), which does the same as
# CHECK_SYMBOL_EXISTS(), but in C++.
#
# 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
macro(CHECK_SYMBOL_EXISTS SYMBOL FILES VARIABLE)
if(CMAKE_C_COMPILER_LOADED)
_CHECK_SYMBOL_EXISTS("${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckSymbolExists.c" "${SYMBOL}" "${FILES}" "${VARIABLE}" )
elseif(CMAKE_CXX_COMPILER_LOADED)
_CHECK_SYMBOL_EXISTS("${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeTmp/CheckSymbolExists.cxx" "${SYMBOL}" "${FILES}" "${VARIABLE}" )
else()
message(FATAL_ERROR "CHECK_SYMBOL_EXISTS needs either C or CXX language enabled")
endif()
endmacro()
macro(_CHECK_SYMBOL_EXISTS SOURCEFILE SYMBOL FILES VARIABLE)
if(NOT DEFINED "${VARIABLE}" OR "x${${VARIABLE}}" STREQUAL "x${VARIABLE}")
set(CMAKE_CONFIGURABLE_FILE_CONTENT "/* */\n")
set(MACRO_CHECK_SYMBOL_EXISTS_FLAGS ${CMAKE_REQUIRED_FLAGS})
if(CMAKE_REQUIRED_LIBRARIES)
set(CHECK_SYMBOL_EXISTS_LIBS
LINK_LIBRARIES ${CMAKE_REQUIRED_LIBRARIES})
else()
set(CHECK_SYMBOL_EXISTS_LIBS)
endif()
if(CMAKE_REQUIRED_INCLUDES)
set(CMAKE_SYMBOL_EXISTS_INCLUDES
"-DINCLUDE_DIRECTORIES:STRING=${CMAKE_REQUIRED_INCLUDES}")
else()
set(CMAKE_SYMBOL_EXISTS_INCLUDES)
endif()
foreach(FILE ${FILES})
string(APPEND CMAKE_CONFIGURABLE_FILE_CONTENT
"#include <${FILE}>\n")
endforeach()
string(APPEND CMAKE_CONFIGURABLE_FILE_CONTENT
"\nint main(int argc, char** argv)\n{\n (void)argv;\n#ifndef ${SYMBOL}\n return ((int*)(&${SYMBOL}))[argc];\n#else\n (void)argc;\n return 0;\n#endif\n}\n")
configure_file("${CMAKE_ROOT}/Modules/CMakeConfigurableFile.in"
"${SOURCEFILE}" @ONLY)
if(NOT CMAKE_REQUIRED_QUIET)
message(STATUS "Looking for ${SYMBOL}")
endif()
try_compile(${VARIABLE}
${CMAKE_BINARY_DIR}
"${SOURCEFILE}"
COMPILE_DEFINITIONS ${CMAKE_REQUIRED_DEFINITIONS}
${CHECK_SYMBOL_EXISTS_LIBS}
CMAKE_FLAGS
-DCOMPILE_DEFINITIONS:STRING=${MACRO_CHECK_SYMBOL_EXISTS_FLAGS}
"${CMAKE_SYMBOL_EXISTS_INCLUDES}"
OUTPUT_VARIABLE OUTPUT)
if(${VARIABLE})
if(NOT CMAKE_REQUIRED_QUIET)
message(STATUS "Looking for ${SYMBOL} - found")
endif()
set(${VARIABLE} 1 CACHE INTERNAL "Have symbol ${SYMBOL}")
file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
"Determining if the ${SYMBOL} "
"exist passed with the following output:\n"
"${OUTPUT}\nFile ${SOURCEFILE}:\n"
"${CMAKE_CONFIGURABLE_FILE_CONTENT}\n")
else()
if(NOT CMAKE_REQUIRED_QUIET)
message(STATUS "Looking for ${SYMBOL} - not found")
endif()
set(${VARIABLE} "" CACHE INTERNAL "Have symbol ${SYMBOL}")
file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
"Determining if the ${SYMBOL} "
"exist failed with the following output:\n"
"${OUTPUT}\nFile ${SOURCEFILE}:\n"
"${CMAKE_CONFIGURABLE_FILE_CONTENT}\n")
endif()
endif()
endmacro()