1 files changed, 70 insertions, 0 deletions
diff --git a/build/prelude.mk b/build/prelude.mk
new file mode 100644
index 0000000..c25dea4
--- /dev/null
+++ b/build/prelude.mk
@@ -0,0 +1,70 @@
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Common makefile utilities.  Compatible with both GNU make and most BSD makes.
+
+# BSD make will chdir into ${.OBJDIR} by default, unless we tell it not to
+.OBJDIR: .
+
+# We don't use any suffix rules
+.SUFFIXES:
+
+# GNU make has $^ for the full list of targets, while BSD make has $> and the
+# long-form ${.ALLSRC}.  We could write $^ $> to get them both, but that would
+# break if one of them implemented support for the other.  So instead, bring
+# BSD's ${.ALLSRC} to GNU.
+.ALLSRC ?= $^
+
+# Installation paths
+DESTDIR ?=
+PREFIX ?= /usr
+MANDIR ?= ${PREFIX}/share/man
+
+# Configurable executables
+CC ?= cc
+INSTALL ?= install
+MKDIR ?= mkdir -p
+PKG_CONFIG ?= pkg-config
+RM ?= rm -f
+
+# GNU and BSD make have incompatible syntax for conditionals, but we can do a
+# lot with just nested variable expansion.  We use "y" as the canonical
+# truthy value, and "" (the empty string) as the canonical falsey value.
+#
+# To normalize a boolean, use ${TRUTHY,${VAR}}, which expands like this:
+#
+#     VAR=y      ${TRUTHY,${VAR}} => ${TRUTHY,y}     => y
+#     VAR=1      ${TRUTHY,${VAR}} => ${TRUTHY,1}     => y
+#     VAR=n      ${TRUTHY,${VAR}} => ${TRUTHY,n}     =>   [empty]
+#     VAR=other  ${TRUTHY,${VAR}} => ${TRUTHY,other} =>   [empty]
+#     VAR=       ${TRUTHY,${VAR}} => ${TRUTHY,}      =>   [empty]
+#
+# Inspired by https://github.com/wahern/autoguess
+TRUTHY,y := y
+TRUTHY,1 := y
+
+# Boolean operators are also implemented with nested expansion
+NOT, := y
+
+# Normalize ${V} to either "y" or ""
+export XV=${TRUTHY,${V}}
+
+# Suppress output unless V=1
+Q, := @
+Q  := ${Q,${XV}}
+
+# Show full commands with `make V=1`, otherwise short summaries
+MSG = @build/msg.sh
+
+# cat a file if V=1
+VCAT,y := @cat
+VCAT,  := @:
+VCAT   := ${VCAT,${XV}}
+
+# All external dependencies
+ALL_PKGS := \
+    libacl \
+    libcap \
+    libselinux \
+    liburing \
+    oniguruma