build: Refactor configuration

We now use a recursive make invocation to do the work of `make config`.
The new implementation is also compatible with GNU make 3.81 found on
macOS.

1 files changed, 77 insertions, 0 deletions

diff --git a/config/config.mk b/config/config.mk
new file mode 100644
index 0000000..c8d7f19
--- /dev/null
+++ b/config/config.mk
@@ -0,0 +1,77 @@
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Makefile fragment that implements `make config`
+
+include config/prelude.mk
+include config/exports.mk
+
+# Makefile fragments generated by `make config`
+MKS := \
+    ${GEN}/vars.mk \
+    ${GEN}/flags.mk \
+    ${GEN}/deps.mk \
+    ${GEN}/objs.mk \
+    ${GEN}/pkgs.mk
+
+# The main configuration file, which includes the others
+${CONFIG}: ${MKS}
+	${MSG} "[ GEN] $@"
+	@printf '# %s\n' "$@" >$@
+	@printf 'include $${GEN}/%s\n' ${.ALLSRC:${GEN}/%=%} >>$@
+	${VCAT} ${CONFIG}
+.PHONY: ${CONFIG}
+
+# Saves the configurable variables
+${GEN}/vars.mk::
+	@${MKDIR} ${@D}
+	${MSG} "[ GEN] $@"
+	@printf '# %s\n' "$@" >$@
+	@printf 'PREFIX := %s\n' "$$XPREFIX" >>$@
+	@printf 'MANDIR := %s\n' "$$XMANDIR" >>$@
+	@printf 'OS := %s\n' "$${OS:-$$(uname)}" >>$@
+	@printf 'ARCH := %s\n' "$${ARCH:-$$(uname -m)}" >>$@
+	@printf 'CC := %s\n' "$$XCC" >>$@
+	@printf 'INSTALL := %s\n' "$$XINSTALL" >>$@
+	@printf 'MKDIR := %s\n' "$$XMKDIR" >>$@
+	@printf 'RM := %s\n' "$$XRM" >>$@
+	@printf 'PKGS :=\n' >>$@
+	${VCAT} $@
+
+# Sets the build flags.  This depends on vars.mk and uses a recursive make so
+# that the default flags can depend on variables like ${OS}.
+${GEN}/flags.mk: ${GEN}/vars.mk
+	@+${MAKE} -sf config/flags.mk
+.PHONY: ${GEN}/flags.mk
+
+# Check for dependency generation support
+${GEN}/deps.mk: ${GEN}/flags.mk
+	@+${MAKE} -sf config/deps.mk
+.PHONY: ${GEN}/deps.mk
+
+# Lists file.o: file.c dependencies
+${GEN}/objs.mk::
+	@${MKDIR} ${@D}
+	${MSG} "[ GEN] $@"
+	@printf '# %s\n' "$@" >$@
+	@for obj in ${OBJS:${OBJ}/%.o=%}; do printf '$${OBJ}/%s.o: %s.c\n' "$$obj" "$$obj"; done >>$@
+
+# External dependencies
+PKG_MKS := \
+    ${GEN}/libacl.mk \
+    ${GEN}/libcap.mk \
+    ${GEN}/libselinux.mk \
+    ${GEN}/liburing.mk \
+    ${GEN}/oniguruma.mk
+
+# Auto-detect dependencies and their build flags
+${GEN}/pkgs.mk: ${PKG_MKS}
+	@printf '# %s\n' "$@" >$@
+	@printf 'include $${GEN}/%s\n' ${.ALLSRC:${GEN}/%=%} >>$@
+	@+${MAKE} -sf config/pkgs.mk
+.PHONY: ${GEN}/pkgs.mk
+
+# Auto-detect dependencies
+${PKG_MKS}: ${GEN}/flags.mk
+	@+${MAKE} -sf config/pkg.mk TARGET=$@
+.PHONY: ${PKG_MKS}