-- Copyright (C) 1997-2016 Sam Lantinga <slouken@libsdl.org>

--

-- This software is provided 'as-is', without any express or implied

-- warranty.  In no event will the authors be held liable for any damages

-- arising from the use of this software.

--

-- Permission is granted to anyone to use this software for any purpose,

-- including commercial applications, and to alter it and redistribute it

-- freely.

--

-- Meta-build system using premake created and maintained by

-- Benjamin Henning <b.henning@digipen.edu>

--[[

sdl_check_compile.lua

	This file provides various utility functions which allow the meta-build

	system to perform more complex dependency checking than premake initially

	allows. This is done using the (currently) GCC toolchain to build generated

	C files which try to import certain headers, link to certain functions, link

	to certain libraries, or a combination of the above. It supports providing a

	custom source to try and build, link, and/or run per the implementation's

	choice, so the possibilities are nearly endless with that this system is

	capable of, though it could always do with more flexibility.

]]

local cxx = "gcc"

local cxx_flags = ""

local cxx_io_flags = "-o premakecheck.o -c premakecheck.c 2> /dev/null"

local cxx_includes = { }

local link = "gcc"

local link_flags = ""

local link_io_flags = "-o premakecheck.out premakecheck.o"

local link_end = " 2> /dev/null"

local run = "./premakecheck.out"

local run_flags = ""

local run_io_flags = " > ./premakecheck.stdout"

local checked_printf = false

local has_printf = false

-- Set the application used to compile the generated files.

function set_cxx(compiler)

	cxx = compiler

end

-- Set custom flags for the compiler.

function set_cxx_flags(flags)

	cxx_flags = flags

end

-- Include a search directory for libraries.

local function include_library_dir(dir)

	link_flags = link_flags .. "-L" .. dir .. " "

end

-- Include a library to be linked durnig the link step.

local function link_library(lib)

	link_flags = link_flags .. "-l" .. lib .. " "

end

-- Reset the link flags.

local function reset_link_flags()

	link_flags = ""

end

-- Creates the build command line to be executed.

local function build_compile_line()

	return cxx .. " " .. cxx_flags .. " " .. cxx_io_flags

end

-- Creates the link command line to be executed.

local function build_link_line()

	return link .. " " .. link_io_flags .. " " .. link_flags .. link_end

end

-- Create the run line to be executed.

local function build_run_line()

	return run .. " " .. run_flags .. " " .. run_io_flags

end

-- Builds a list of preprocessor include directives for all the include files

-- successfully found so far by these functions, so as to perform automatic

-- feature checking for the clientside code.

local function build_includes()

	local includes = ""

	for _,v in ipairs(cxx_includes) do

		includes = includes .. '#include "' .. v .. '"\n'

	end

	return includes

end

-- Cleanup the generated build environment.

local function cleanup_build()

	os.remove("./premakecheck.c")

	os.remove("./premakecheck.o")

	os.remove("./premakecheck.out")

	os.remove("./premakecheck.stdout")

end

-- Check if a source builds, links, and or/runs, where running depends on

-- linking and linking depends on building. The return from this function is

-- a triple, where the first is a boolean value indicating if it successfully

-- was built, the second is a boolean value indicating if it successfully

-- linked, and the third represents nil if it was not run or run correctly, or

-- the output from the program executed (may be empty for no output).

local function check_build_source(source, link, run)

	local file = fileopen("./premakecheck.c", "wt")

	file:write(source)

	file:close()

	local result = os.execute(build_compile_line())

	if not link then

		cleanup_build()

		if result == 0 then

			return true, false, nil -- compile, no link, no run

		end

		return false, false, nil -- no compile, no link, no run

	end

	-- try linking, too

	if result ~= 0 then

		-- can't link if it doesn't compile

		cleanup_build()

		return false, false, nil -- no compile, no link, no run

	end

	result = os.execute(build_link_line())

	if not run or result ~= 0 then -- have to link to run

		cleanup_build()

		return true, result == 0, nil -- compile, maybe link, no run

	end

	result = os.execute(build_run_line())

	local output = readfile("./premakecheck.stdout", "rt")

	cleanup_build()

	return true, true, output -- compile, link, ran

end

-- Given C source code, determine whether the source code will compile in the

-- present environment. Returns true if the source was successfully compiled, or

-- false if otherwise.

function check_cxx_source_compiles(source)

	local r1, _, __ = check_build_source(source, false, false)

	return r1

end

-- Given C source code, determine whether the source code can be built into a

-- working executable. That is, it will check if the code both compiles and

-- links. Returns true if the code was successfully built (compiled and linked),

-- or false if otherwise.

function check_cxx_source_builds(source)

	local r1, r2, _ = check_build_source(source, true, false)

	return r1 and r2

end

-- Given C source code, attempt to compile, link, and execute the source code.

-- This function will return two values. The first is a boolean indicating

-- whether the source code was successfully run (meaning it was compiled, built,

-- and ran successfully), and the second value returned is the actual output

-- from running the application, or nil if it did not run correctly or was not

-- built. The output may be an empty string if the code does not print anything

-- to stdout.

function check_cxx_source_runs(source)

	local r1, r2, r3 = check_build_source(source, true, true)

	return r1 and r2 and (r3 ~= nil), r3

end

-- Given a header file, check whether the header file is visible to the compiler

-- in the given environment. Returns a boolean indicating thus. If a header file

-- is found in either of these functions, it will be added to a list of headers

-- that can be used in subsequent dependency checks.

function check_include_file(inc)

	return check_include_files(inc)

end

-- Given a variable list of header files, check whether all of the includes are

-- visible in the given environment. Every file must be included in order for

-- this function to return true.

function check_include_files(...)

	local source = ""

	for _, v in ipairs{...} do

		source = source .. '#include "' .. v .. '"\n'

	end

	local result = check_cxx_source_compiles(source)

	if result then

		for _, v in ipairs{...} do

			table.insert(cxx_includes, v)

		end

	end

	return result

end

-- Given a directory, determine whether the directory contains any header files.

-- Unfortunately it does assume the extension is .h, but this can be altered in

-- future versions of this software. The function returns true if the directory

-- (or any of its subdirectories) contain .h files, or false if otherwise (such

-- as if the directory does not exist).

function check_include_directory(incDir)

	incDir = incDir:gsub("\\", "/"):gsub("//", "/")

	if incDir:sub(#incDir, #incDir) ~= "/" then

		incDir = incDir .. "/"

	end

	return #os.matchfiles(incDir .. "**.h") > 0

end

-- Given a variable list of directories, iteratively check if each one contains

-- header files, per the functionality of check_include_directory. This function

-- returns true if and only if every listed directory or its subdirectories

-- contain .h files.

function check_include_directories(...)

	for _, v in ipairs{...} do

		if not check_include_directory(v) then

			return false

		end

	end

	return true

end

-- Given a function name, attempt to determine whether the function can be found

-- within all of the known include files. Known include files are derived from

-- the check_include_file(s) functions.

function check_function_exists(func)

	local source = build_includes()

	source = source .. 'int main(int argc, char **argv) {\n'

	source = source .. '\tvoid *check = (void *) ' .. func .. ';\n'

	source = source .. '\treturn 0;\n'

	return check_cxx_source_builds(source .. '}')

end

-- Given a library, a function that must exist within the library, and an

-- include file prototyping the function, this function determines whether those

-- three variables are able to build a working executable. That is, if a

-- function can be properly linked to using a given library, then the library

-- can be assumed to exist. Returns true if and only if the function was

-- correctly linked to.

function check_library_exists(lib, func, inc)

	local source = build_includes()

	if inc ~= nil then

		source = source .. '#include "' .. inc .. '"\n'

	end

	source = source .. 'int main(int argc, char **argv) {\n'

	source = source .. '\tvoid *check = (void *) ' .. func .. ';\n'

	source = source .. '\treturn 0;\n'

	if lib ~= nil then

		link_library(lib)

	end

	local result = check_cxx_source_builds(source .. '}')

	reset_link_flags()

	return result

end

-- This is a merge variable list version of the check_library_exists function.

-- The thing to note with this function is that it will return true for the

-- first library found to correctly link to the function. This function is used

-- to determine whether the function is found in a list of libraries, not if it

-- is found in every one of the libraries.

function check_library_exists_multiple(func, inc, ...)

	for _,v in ipairs{...} do

		if check_library_exists(v, func, inc) then

			return true

		end

	end

	return false

end

-- This is a wrapper for the check_library_exists function that will also

-- attempt to locate the library in question, in case it's not in a path the

-- compiler is already aware of. This function has the same return consequences

-- as check_library_exists.

function check_library_exists_lookup(lib, func, inc)

	local dir = os.findlib(lib)

	if dir == nil then

		return false

	end

	include_library_dir(dir)

	return check_library_exists(lib, func, inc)

end

-- Given a valid C type name, this function generates a program that will print

-- the size of the type using the sizeof operator to the console, then parse the

-- size to indicate the byte size of the type on this platform. The resulting

-- executable is dependent on stdio and the printf function, which it safely

-- checks for behind the scenes. If these dependencies are not found for

-- whatever reason, this function returns 0, otherwise it returns a proper

-- numerical value representing the size of the specified type.

function check_type_size(typename)

	if not checked_printf then

		checked_printf = true

		has_printf = check_include_file("stdio.h") and check_function_exists("printf")

		if not has_printf then

			print("Warning: cannot check the size of a type without stdio and printf.")

		end

	end

	if not has_printf then

		return 0

	end

	local source = '#include "stdio.h"\n'

	source = source .. 'int main(int argc, char **argv) {\n'

	source = source .. '\tprintf("%d", sizeof(' .. typename .. '));\n'

	source = source .. '\treturn 0;\n'

	local success, result = check_cxx_source_runs(source .. '}');

	if not success then

		print("Warning: could not get the size of type: " .. typename)

		return 0

	end

	return tonumber(result)

end