From 751fca09e1a8b48b21cdaf552c19be9cb8a01a4c Mon Sep 17 00:00:00 2001
From: Jeremy Baxter <jeremy@baxters.nz>
Date: Thu, 25 Jan 2024 21:12:12 +1300
Subject: [PATCH] switch to modular configure-based buildsystem

---
 .gitignore |   1 +
 Makefile   |  13 +++----
 README.md  |   1 +
 configure  | 112 +++++++++++++++++++++++++++++++++++++++++++++++++++++
 4 files changed, 119 insertions(+), 8 deletions(-)
 create mode 100755 configure

diff --git a/.gitignore b/.gitignore
index 69f4dfa..e973dcf 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,4 +6,5 @@ luac
 *.o
 *.so
 
+config.mk
 include/
diff --git a/Makefile b/Makefile
index de4c59d..0ec102e 100644
--- a/Makefile
+++ b/Makefile
@@ -1,14 +1,11 @@
+include config.mk
+
 PREFIX = /usr/local
 MANPREFIX = ${PREFIX}/man
 
-CC       = cc
-CFLAGS   = -std=c99 -pedantic -fpic -O2 -Iexternal/lua -Wall -Wextra
-CPPFLAGS = -D_DEFAULT_SOURCE
-LDFLAGS  = -lm
-
-# Enable readline
-#CPPFLAGS += -DLUA_USE_READLINE
-#LDFLAGS  += -lreadline
+CC       = ${_CC}
+CFLAGS   = -std=c99 ${_CFLAGS} -pedantic -Iexternal/lua -Wall -Wextra -D_DEFAULT_SOURCE
+LDFLAGS  = -lm ${_LDFLAGS}
 
 OBJS = callisto.o lcl.o lenviron.o lextra.o lfs.o ljson.o lprocess.o util.o
 LIBS = libcallisto.a liblua.a
diff --git a/README.md b/README.md
index a11c70b..debb754 100644
--- a/README.md
+++ b/README.md
@@ -59,6 +59,7 @@ Untar it then enter the directory with Callisto's source code.
 
 After that, run
 
+    ./configure
     make
 
 to compile Callisto and all its dependencies.
diff --git a/configure b/configure
new file mode 100755
index 0000000..f2e23fc
--- /dev/null
+++ b/configure
@@ -0,0 +1,112 @@
+#!/usr/bin/env sh
+# simple and flexible configure script for people who don't like to waste time
+# licensed to the public domain
+
+set -e
+
+mkf=config.mk
+
+# utility functions
+
+present () {
+	command -v "$1" 1>/dev/null 2>/dev/null
+}
+using () {
+	printf "using $1\n"
+}
+error () {
+	>&2 printf "$(basename $0): $1\n"
+	exit 1
+}
+
+# generators
+
+## C compiler
+gen_CC () {
+	if ! [ -z "$cc" ]; then
+		using "$cc"
+		return 0
+	fi
+	if present clang; then
+		cc=clang
+	elif present cc; then
+		cc=cc
+	elif present gcc; then
+		cc=gcc
+	else
+		error "C compiler not found, please acquire a copy of LLVM Clang or the GNU C compiler"
+	fi
+
+	using "$cc"
+}
+
+## flags used in the compilation step
+gen_CFLAGS () {
+	if [ -z "$debug" ]; then
+		cflags="-O2"
+	else
+		cflags="-O0 -g"
+	fi
+
+	for flag in $cflags; do
+		using "$flag"
+	done
+}
+
+## flags used in the linking step
+gen_LDFLAGS () {
+	if pkg-config readline; then
+		ldflags="$(pkg-config --libs readline)"
+	fi
+	if present ld.lld; then
+		ldflags="$ldflags -fuse-ld=lld"
+	elif present ld.gold; then
+		ldflags="$ldflags -fuse-ld=gold"
+	fi
+	[ -z "$debug" ] && ldflags="$ldflags -Wl,--gc-sections"
+
+	for flag in $ldflags; do
+		using "$flag"
+	done
+}
+
+# command line interface
+
+while getopts c:dhr ch; do
+	case "$ch" in
+		c) cc="$OPTARG" ;;
+		d) debug=1 ;;
+		r) unset debug ;;
+		h)
+			cat <<EOF
+configure: create an optimised makefile for the current environment
+
+options:
+  -c: force use of a particular compiler
+  -d: build in debug mode, with debug symbols enabled
+  -r: build in release mode with optimisation flags enabled (default)
+  -h: show this help message
+EOF
+			exit 0
+			;;
+		?) exit 1 ;;
+		:) exit 1 ;;
+	esac
+done
+
+# creating the makefile
+
+gen_CC
+gen_CFLAGS
+gen_LDFLAGS
+
+printf '# generated by configure
+
+_CC      = %s
+_CFLAGS  = %s
+_LDFLAGS =%s
+'             \
+	"$cc"     \
+	"$cflags" \
+	"$ldflags"\
+		>"$mkf"