From a554c20592765a09bcc59a008cf4a29abc58aeb4 Mon Sep 17 00:00:00 2001
From: midipix <writeonce@midipix.org>
Date: Nov 11 2016 04:35:25 +0000
Subject: build system: configure: usage(): initial documentation.


---

diff --git a/config.usage b/config.usage
new file mode 100644
index 0000000..2175510
--- /dev/null
+++ b/config.usage
@@ -0,0 +1,77 @@
+configure: a skinny configuration script.
+
+supported switches:
+-------------------
+	--help
+
+	--prefix
+	--bindir
+	--libdir
+	--includedir
+	--syslibdir
+	--mandir
+	--libexecdir
+
+	--build
+	--host
+	--target
+	--arch
+	--toolchain
+	--sysroot
+	--cross-compile
+	--shell
+	--debug
+
+
+supported variables:
+--------------------
+	PREFIX
+	BINDIR
+	LIBDIR
+	INCLUDEDIR
+	LIBDIR
+	MANDIR
+	DOCDIR
+	LIBEXECDIR
+
+	CC
+	CPP
+	CXX
+
+	BUILD
+	HOST
+	TARGET
+	ARCH
+	TOOLCHAIN
+	SYSROOT
+	CROSS_COMPILE
+	SHELL
+
+	CFLAGS
+	CFLAGS_DEBUG
+	CFLAGS_COMMON
+	CFLAGS_CMDLINE
+	CFLAGS_CONFIG
+	CFLAGS_SYSROOT
+	CFLAGS_PATH
+
+	LDFLAGS
+	LDFLAGS_DEBUG
+	LDFLAGS_COMMON
+	LDFLAGS_CMDLINE
+	LDFLAGS_CONFIG
+	LDFLAGS_SYSROOT
+	LDFLAGS_PATH
+
+	PE_SUBSYSTEM
+	PE_IMAGE_BASE
+	PE_CONFIG_DEFS
+
+	ELF_EH_FRAME
+	ELF_HASH_STYLE
+	ELF_CONFIG_DEFS
+
+	NATIVE_CC
+	NATIVE_OS
+	NATIVE_OS_BITS
+	NATIVE_OS_UNDERSCORE
diff --git a/configure b/configure
index 7139ece..a21df9e 100755
--- a/configure
+++ b/configure
@@ -5,6 +5,12 @@
 # as well as both LDFLAGS and LDFLAGS_CMDLINE, however
 # the latter variable of each pair should be preferred.
 
+usage()
+{
+	cat config.usage
+	exit $?
+}
+
 error_msg()
 {
 	echo $@ >&2