#!/bin/sh

fail() {
	echo "$0: $*" >&2
	exit 1
}

host=
target=
gcclibdir=

for arg ; do
	case "$arg" in
	--host=*) host=${arg#*=} ;;
	--target=*) target=${arg#*=} ;;
	--with-cpp=*) DEFAULT_PREPROCESSOR=${arg#*=} ;;
	--with-qbe=*) DEFAULT_QBE=${arg#*=} ;;
	--with-as=*) DEFAULT_ASSEMBLER=${arg#*=} ;;
	--with-ld=*) DEFAULT_LINKER=${arg#*=} ;;
	--with-gcc-libdir=*) gcclibdir=${arg#*=} ;;
	CC=*) CC=${arg#*=} ;;
	CFLAGS=*) CFLAGS=${arg#*=} ;;
	LDFLAGS=*) LDFLAGS=${arg#*=} ;;
	*) fail "unknown option '$arg'"
	esac
done

: ${CC:=cc}
: ${DEFAULT_PREPROCESSOR:=cpp}
: ${DEFAULT_QBE:=qbe}
: ${DEFAULT_ASSEMBLER:=as}
: ${DEFAULT_LINKER:=ld}

printf 'checking host system type... '
test -n "$host" || host=$($CC -dumpmachine 2>/dev/null) || fail "could not determine host"
printf '%s\n' "$host"

printf 'checking target system type...'
test -n "$target" || target=$host
printf '%s\n' "$target"

case "$target" in
x86_64*|amd64*) qbetarget=amd64_sysv ;;
aarch64*)       qbetarget=arm64      ;;
*) fail "unsupported architecture '${target%%-*}'"
esac

gnuc='
	/* specify the GNU C extensions we support */
	"-D", "__GNUC__=1",
	"-D", "__GNUC_MINOR__=0",
'

case "$target" in
*-linux-*musl*)
	case "$target" in
	x86_64*)  dynamiclinker=/lib/ld-musl-x86_64.so.1  ;;
	aarch64*) dynamiclinker=/lib/ld-musl-aarch64.so.1 ;;
	*) fail "unsuported target '$target'"
	esac
	startfiles='"-l", ":crt1.o", "-l", ":crti.o"'
	endfiles='"-l", ":crtn.o", "-l", "c"'
	;;
*-linux-*gnu*)
	case "$target" in
	x86_64*)  dynamiclinker=/lib64/ld-linux-x86-64.so.2 ;;
	aarch64*) dynamiclinker=/lib/ld-linux-aarch64.so.1  ;;
	*) fail "unsuported target '$target'"
	esac
	startfiles='"-l", ":crt1.o", "-l", ":crti.o", "-l", ":crtbegin.o"'
	endfiles='"-l", ":crtend.o", "-l", ":crtn.o", "-l", "c"'
	if [ -z "$gcclibdir" ] ; then
		test "$host" = "$target" || fail "gcc libdir must be specified when building a cross-compiler"
		crtbegin=$($CC -print-file-name=crtbegin.o 2>/dev/null)
		gcclibdir=${crtbegin%/*}
	fi
	linkflags='"-L", "'$gcclibdir'"',
	defines='
	/* prevent glibc from using statement expressions for assert */
	"-D", "__STRICT_ANSI__",
'
	;;
*-*freebsd*)
	dynamiclinker=/libexec/ld-elf.so.1
	startfiles='"-l", ":crt1.o", "-l", ":crti.o"'
	endfiles='"-l", ":crtn.o", "-l", "c"'
	# any value of __GNUC__ will cause FreeBSD's headers to use asm for bswap
	gnuc=
	linkflags='"-L", "/usr/lib"',
	defines='
	"-D", "_Pragma(x)=",
	"-D", "_Nullable=",
	"-D", "_Nonnull=",

	"-D", "__GNUCLIKE_BUILTIN_STDARG",
	"-D", "__GNUCLIKE_BUILTIN_VARARGS",

	/* required to define _RuneLocale, needed by xlocale/_ctype.h */
	"-D", "_USE_CTYPE_INLINE_",
	/* workaround for #42 */
	"-D", "_XLOCALE_INLINE=static inline",
	/* used like attribute after declarator, so _Alignas will not work here */
	"-D", "__aligned(x)=",
	/* TLS is not yet supported (#8) */
	"-D", "__NO_TLS",

	/* disable warnings for redefining _Pragma */
	"-Wno-builtin-macro-redefined",
'
	;;
*)
	fail "unknown target '$target', please create config.h manually"
esac

printf "creating config.h... "
cat >config.h <<EOF
static char *startfiles[]    = {$startfiles};
static char *endfiles[]      = {$endfiles};
static char *preprocesscmd[] = {
	"$DEFAULT_PREPROCESSOR", "-P", "-std=c11",

	/* clear preprocessor GNU C version */
	"-U", "__GNUC__",
	"-U", "__GNUC_MINOR__",

	/* we don't yet support these optional features */
	"-D", "__STDC_NO_ATOMICS__",
	"-D", "__STDC_NO_COMPLEX__",
	"-D", "__STDC_NO_VLA__",

	/* ignore attributes and extension markers */
	"-D", "__attribute__(x)=",
	"-D", "__extension__=",

	/* alternate keywords */
	"-D", "__alignof__=_Alignof",
	"-D", "__inline=inline",
	"-D", "__inline__=inline",
	"-D", "__signed__=signed",
	"-D", "__thread=_Thread_local",
$gnuc$defines};
static char *codegencmd[]    = {"$DEFAULT_QBE", "-t", "$qbetarget"};
static char *assemblecmd[]   = {"$DEFAULT_ASSEMBLER"};
static char *linkcmd[]       = {"$DEFAULT_LINKER", "--dynamic-linker", "$dynamiclinker", $linkflags};
EOF
echo done

printf "creating config.mk... "
cat >config.mk <<EOF
CC=${CC:-cc}
CFLAGS=${CFLAGS:--std=c11 -Wall -Wno-parentheses -Wno-switch -g -pipe}
LDFLAGS=$LDFLAGS
EOF
echo done