67 files changed, 798 insertions, 572 deletions

diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 3890bb0..e47600b 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -107,7 +107,7 @@ jobs:
                 gmake \
                 oniguruma
             jobs=$(sysctl -n hw.ncpu)
-            gmake -j$jobs config
+            ./configure MAKE=gmake
             gmake -j$jobs check TEST_FLAGS="--sudo --verbose=skipped"
 
   netbsd:
@@ -133,7 +133,7 @@ jobs:
                 pkgconf \
                 tcl-expect
             jobs=$(sysctl -n hw.ncpu)
-            make -j$jobs config
+            ./configure
             make -j$jobs check TEST_FLAGS="--sudo --verbose=skipped"
 
   dragonflybsd:
@@ -165,7 +165,7 @@ jobs:
           run: |
             chown -R action:action .
             jobs=$(sysctl -n hw.ncpu)
-            sudo -u action make config
+            sudo -u action ./configure
             sudo -u action make -j$jobs check TEST_FLAGS="--sudo --verbose=skipped"
 
   omnios:
@@ -198,5 +198,5 @@ jobs:
             PATH="/usr/xpg4/bin:$PATH"
             chown -R action:staff .
             jobs=$(getconf NPROCESSORS_ONLN)
-            sudo -u action gmake config
+            sudo -u action ./configure MAKE=gmake
             sudo -u action gmake -j$jobs check TEST_FLAGS="--sudo --verbose=skipped"
diff --git a/.github/workflows/codecov.yml b/.github/workflows/codecov.yml
index 2245f40..6aaace6 100644
--- a/.github/workflows/codecov.yml
+++ b/.github/workflows/codecov.yml
@@ -25,7 +25,7 @@ jobs:
 
       - name: Generate coverage
         run: |
-          make config GCOV=y
+          ./configure --enable-gcov
           make -j$(nproc) check TEST_FLAGS="--sudo"
           gcov -abcfpu obj/*/*.o
 
diff --git a/.github/workflows/codeql.yml b/.github/workflows/codeql.yml
index c21fda5..a0b8fe3 100644
--- a/.github/workflows/codeql.yml
+++ b/.github/workflows/codeql.yml
@@ -41,7 +41,7 @@ jobs:
 
       - name: Configure
         run: |
-          make -j$(nproc) config
+          ./configure
 
       - name: Initialize CodeQL
         uses: github/codeql-action/init@v3
diff --git a/Makefile b/Makefile
index 981c322..d89f3b6 100644
--- a/Makefile
+++ b/Makefile
@@ -1,111 +1,99 @@
 # Copyright © Tavian Barnes <tavianator@tavianator.com>
 # SPDX-License-Identifier: 0BSD
 
-# This Makefile implements the configuration and build steps for bfs.  It is
-# portable to both GNU make and most BSD make implementations.  To build bfs,
-# run
+# To build bfs, run
 #
-#     $ make config
+#     $ ./configure
 #     $ make
 
 # Utilities and GNU/BSD portability
-include config/prelude.mk
+include build/prelude.mk
 
 # The default build target
 default: bfs
 .PHONY: default
 
 # Include the generated build config, if it exists
--include ${CONFIG}
+-include gen/config.mk
 
-## Configuration phase (`make config`)
-
-# The configuration goal itself
-config::
-	@+${MAKE} -sf config/config.mk
+## Configuration phase (`./configure`)
 
 # bfs used to have flag-like targets (`make release`, `make asan ubsan`, etc.).
 # Direct users to the new configuration system.
 asan lsan msan tsan ubsan gcov lint release::
-	@printf 'error: `%s %s` is no longer supported. ' "${MAKE}" $@ >&2
-	@printf 'Use `%s config %s=y` instead.\n' "${MAKE}" $$(echo $@ | tr 'a-z' 'A-Z') >&2
+	@printf 'error: `%s %s` is no longer supported. Use `./configure --enable-%s` instead.\n' \
+	    "${MAKE}" $@ $@ >&2
 	@false
 
-# Print an error if `make` is run before `make config`
-${CONFIG}::
+# Print an error if `make` is run before `./configure`
+gen/config.mk::
 	@if ! [ -e $@ ]; then \
-	    printf 'error: You must run `%s config` before `%s`.\n' "${MAKE}" "${MAKE}" >&2; \
+	    printf 'error: You must run `./configure` before `%s`.\n' "${MAKE}" >&2; \
 	    false; \
 	fi
 
 ## Build phase (`make`)
 
 # The main binary
-bfs: ${BIN}/bfs
+bfs: bin/bfs
 .PHONY: bfs
 
 # All binaries
 BINS := \
-    ${BIN}/bfs \
-    ${BIN}/tests/mksock \
-    ${BIN}/tests/units \
-    ${BIN}/tests/xspawnee \
-    ${BIN}/tests/xtouch
+    bin/bfs \
+    bin/tests/mksock \
+    bin/tests/units \
+    bin/tests/xspawnee \
+    bin/tests/xtouch
 
 all: ${BINS}
 .PHONY: all
 
-# Group relevant flags together
-ALL_CFLAGS = ${CPPFLAGS} ${CFLAGS} ${DEPFLAGS}
-ALL_LDFLAGS = ${CFLAGS} ${LDFLAGS}
-
 # The main binary
-${BIN}/bfs: ${LIBBFS} ${OBJ}/src/main.o
+bin/bfs: ${LIBBFS} obj/src/main.o
 
 ${BINS}:
 	@${MKDIR} ${@D}
-	+${MSG} "[ LD ] ${TGT}" ${CC} ${ALL_LDFLAGS} ${.ALLSRC} ${LDLIBS} -o $@
+	+${MSG} "[ LD ] $@" ${CC} ${CFLAGS} ${LDFLAGS} ${.ALLSRC} ${LDLIBS} -o $@
 	${POSTLINK}
 
 # Get the .c file for a .o file
-_CSRC = ${@:${OBJ}/%.o=%.c}
-CSRC = ${_CSRC:gen/%=${GEN}/%}
+CSRC = ${@:obj/%.o=%.c}
 
-# Depend on ${CONFIG} to make sure `make config` runs first, and to rebuild when
-# the configuration changes
-${OBJS}: ${CONFIG}
+# Rebuild when the configuration changes
+${OBJS}: gen/config.mk
 	@${MKDIR} ${@D}
-	${MSG} "[ CC ] ${_CSRC}" ${CC} ${ALL_CFLAGS} -c ${CSRC} -o $@
+	${MSG} "[ CC ] ${CSRC}" ${CC} ${CPPFLAGS} ${CFLAGS} -c ${CSRC} -o $@
 
 # Save the version number to this file, but only update version.c if it changes
-${GEN}/version.c.new::
+gen/version.c.new::
 	@${MKDIR} ${@D}
 	@printf 'const char bfs_version[] = "' >$@
 	@if [ "$$VERSION" ]; then \
 	    printf '%s' "$$VERSION"; \
-	elif test -d .git && command -v git >/dev/null 2>&1; then \
-	    git describe --always --dirty; \
+	elif test -e src/../.git && command -v git >/dev/null 2>&1; then \
+	    git -C src/.. describe --always --dirty; \
 	else \
-	    echo "3.1.3"; \
+	    echo "3.2"; \
 	fi | tr -d '\n' >>$@
 	@printf '";\n' >>$@
 
-${GEN}/version.c: ${GEN}/version.c.new
+gen/version.c: gen/version.c.new
 	@test -e $@ && cmp -s $@ ${.ALLSRC} && rm ${.ALLSRC} || mv ${.ALLSRC} $@
 
-${OBJ}/gen/version.o: ${GEN}/version.c
+obj/gen/version.o: gen/version.c
 
 ## Test phase (`make check`)
 
 # Unit test binaries
 UTEST_BINS := \
-    ${BIN}/tests/units \
-    ${BIN}/tests/xspawnee
+    bin/tests/units \
+    bin/tests/xspawnee
 
 # Integration test binaries
 ITEST_BINS := \
-    ${BIN}/tests/mksock \
-    ${BIN}/tests/xtouch
+    bin/tests/mksock \
+    bin/tests/xtouch
 
 # Build (but don't run) test binaries
 tests: ${UTEST_BINS} ${ITEST_BINS}
@@ -117,45 +105,45 @@ check: unit-tests integration-tests
 
 # Run the unit tests
 unit-tests: ${UTEST_BINS}
-	${MSG} "[TEST] tests/units" ${BIN}/tests/units
+	${MSG} "[TEST] tests/units" bin/tests/units
 .PHONY: unit-tests
 
-${BIN}/tests/units: \
+bin/tests/units: \
     ${UNIT_OBJS} \
     ${LIBBFS}
 
-${BIN}/tests/xspawnee: \
-    ${OBJ}/tests/xspawnee.o
+bin/tests/xspawnee: \
+    obj/tests/xspawnee.o
 
 # The different flag combinations we check
 INTEGRATIONS := default dfs ids eds j1 j2 j3 s
 INTEGRATION_TESTS := ${INTEGRATIONS:%=check-%}
 
 # Check just `bfs`
-check-default: ${BIN}/bfs ${ITEST_BINS}
+check-default: bin/bfs ${ITEST_BINS}
 	+${MSG} "[TEST] bfs" \
-	    ./tests/tests.sh --make="${MAKE}" --bfs="${BIN}/bfs" ${TEST_FLAGS}
+	    ./tests/tests.sh --make="${MAKE}" --bfs="bin/bfs" ${TEST_FLAGS}
 
 # Check the different search strategies
-check-dfs check-ids check-eds: ${BIN}/bfs ${ITEST_BINS}
+check-dfs check-ids check-eds: bin/bfs ${ITEST_BINS}
 	+${MSG} "[TEST] bfs -S ${@:check-%=%}" \
-	    ./tests/tests.sh --make="${MAKE}" --bfs="${BIN}/bfs -S ${@:check-%=%}" ${TEST_FLAGS}
+	    ./tests/tests.sh --make="${MAKE}" --bfs="bin/bfs -S ${@:check-%=%}" ${TEST_FLAGS}
 
 # Check various flags
-check-j1 check-j2 check-j3 check-s: ${BIN}/bfs ${ITEST_BINS}
+check-j1 check-j2 check-j3 check-s: bin/bfs ${ITEST_BINS}
 	+${MSG} "[TEST] bfs -${@:check-%=%}" \
-	    ./tests/tests.sh --make="${MAKE}" --bfs="${BIN}/bfs -${@:check-%=%}" ${TEST_FLAGS}
+	    ./tests/tests.sh --make="${MAKE}" --bfs="bin/bfs -${@:check-%=%}" ${TEST_FLAGS}
 
 # Run the integration tests
 integration-tests: ${INTEGRATION_TESTS}
 .PHONY: integration-tests
 
-${BIN}/tests/mksock: \
-    ${OBJ}/tests/mksock.o \
+bin/tests/mksock: \
+    obj/tests/mksock.o \
     ${LIBBFS}
 
-${BIN}/tests/xtouch: \
-    ${OBJ}/tests/xtouch.o \
+bin/tests/xtouch: \
+    obj/tests/xtouch.o \
     ${LIBBFS}
 
 # `make distcheck` configurations
@@ -176,15 +164,17 @@ distcheck:
 .PHONY: distcheck
 
 # Per-distcheck configuration
-DISTCHECK_CONFIG_asan := ASAN=y UBSAN=y
-DISTCHECK_CONFIG_msan := MSAN=y UBSAN=y CC=clang
-DISTCHECK_CONFIG_tsan := TSAN=y UBSAN=y CC=clang
+DISTCHECK_CONFIG_asan := --enable-asan --enable-ubsan
+DISTCHECK_CONFIG_msan := --enable-msan --enable-ubsan CC=clang
+DISTCHECK_CONFIG_tsan := --enable-tsan --enable-ubsan CC=clang
 DISTCHECK_CONFIG_m32 := EXTRA_CFLAGS="-m32" PKG_CONFIG_LIBDIR=/usr/lib32/pkgconfig
-DISTCHECK_CONFIG_release := RELEASE=y
+DISTCHECK_CONFIG_release := --enable-release
 
 ${DISTCHECKS}::
-	+${MAKE} -rs BUILDDIR=${BUILDDIR}/$@ config ${DISTCHECK_CONFIG_${@:distcheck-%=%}}
-	+${MAKE} -s BUILDDIR=${BUILDDIR}/$@ check TEST_FLAGS="--sudo --verbose=skipped"
+	@${MKDIR} $@
+	@+cd $@ \
+	    && ../configure ${DISTCHECK_CONFIG_${@:distcheck-%=%}} \
+	    && ${MAKE} -s check TEST_FLAGS="--sudo --verbose=skipped"
 
 ## Packaging (`make install`)
 
@@ -193,44 +183,49 @@ DEST_MANDIR := ${DESTDIR}${MANDIR}
 
 install::
 	${Q}${MKDIR} ${DEST_PREFIX}/bin
-	${MSG} "[INSTALL] bin/bfs" \
-	    ${INSTALL} -m755 ${BIN}/bfs ${DEST_PREFIX}/bin/bfs
+	${MSG} "[INST] bin/bfs" \
+	    ${INSTALL} -m755 bin/bfs ${DEST_PREFIX}/bin/bfs
 	${Q}${MKDIR} ${DEST_MANDIR}/man1
-	${MSG} "[INSTALL] man/man1/bfs.1" \
+	${MSG} "[INST] man/man1/bfs.1" \
 	    ${INSTALL} -m644 docs/bfs.1 ${DEST_MANDIR}/man1/bfs.1
 	${Q}${MKDIR} ${DEST_PREFIX}/share/bash-completion/completions
-	${MSG} "[INSTALL] completions/bfs.bash" \
+	${MSG} "[INST] completions/bfs.bash" \
 	    ${INSTALL} -m644 completions/bfs.bash ${DEST_PREFIX}/share/bash-completion/completions/bfs
 	${Q}${MKDIR} ${DEST_PREFIX}/share/zsh/site-functions
-	${MSG} "[INSTALL] completions/bfs.zsh" \
+	${MSG} "[INST] completions/bfs.zsh" \
 	    ${INSTALL} -m644 completions/bfs.zsh ${DEST_PREFIX}/share/zsh/site-functions/_bfs
 	${Q}${MKDIR} ${DEST_PREFIX}/share/fish/vendor_completions.d
-	${MSG} "[INSTALL] completions/bfs.fish" \
+	${MSG} "[INST] completions/bfs.fish" \
 	    ${INSTALL} -m644 completions/bfs.fish ${DEST_PREFIX}/share/fish/vendor_completions.d/bfs.fish
 
 uninstall::
-	${RM} ${DEST_PREFIX}/share/bash-completion/completions/bfs
-	${RM} ${DEST_PREFIX}/share/zsh/site-functions/_bfs
-	${RM} ${DEST_PREFIX}/share/fish/vendor_completions.d/bfs.fish
-	${RM} ${DEST_MANDIR}/man1/bfs.1
-	${RM} ${DEST_PREFIX}/bin/bfs
+	${MSG} "[ RM ] completions/bfs.bash" \
+	    ${RM} ${DEST_PREFIX}/share/bash-completion/completions/bfs
+	${MSG} "[ RM ] completions/bfs.zsh" \
+	    ${RM} ${DEST_PREFIX}/share/zsh/site-functions/_bfs
+	${MSG} "[ RM ] completions/bfs.fish" \
+	    ${RM} ${DEST_PREFIX}/share/fish/vendor_completions.d/bfs.fish
+	${MSG} "[ RM ] man/man1/bfs.1" \
+	    ${RM} ${DEST_MANDIR}/man1/bfs.1
+	${MSG} "[ RM ] bin/bfs" \
+	    ${RM} ${DEST_PREFIX}/bin/bfs
 
 # Check that `make install` works and `make uninstall` removes everything
 check-install::
-	+${MAKE} install DESTDIR=${BUILDDIR}/pkg
-	+${MAKE} uninstall DESTDIR=${BUILDDIR}/pkg
-	${BIN}/bfs ${BUILDDIR}/pkg -not -type d -print -exit 1
-	${RM} -r ${BUILDDIR}/pkg
+	+${MAKE} install DESTDIR=pkg
+	+${MAKE} uninstall DESTDIR=pkg
+	bin/bfs pkg -not -type d -print -exit 1
+	${RM} -r pkg
 
 ## Cleanup (`make clean`)
 
 # Clean all build products
 clean::
 	${MSG} "[ RM ] bin obj" \
-	    ${RM} -r ${BIN} ${OBJ}
+	    ${RM} -r bin obj
 
 # Clean everything, including generated files
 distclean: clean
 	${MSG} "[ RM ] gen" \
-	    ${RM} -r ${GEN} ${DISTCHECKS}
+	    ${RM} -r gen ${DISTCHECKS}
 .PHONY: distclean
diff --git a/README.md b/README.md
index b95c16b..b9aad82 100644
--- a/README.md
+++ b/README.md
@@ -333,7 +333,7 @@ Once you have the dependencies, you can build <code>bfs</code>.
 Download one of the [releases](https://github.com/tavianator/bfs/releases) or clone the [git repo](https://github.com/tavianator/bfs).
 Then run
 
-    $ make config
+    $ ./configure
     $ make
 
 This will build the `./bin/bfs` binary.
@@ -343,7 +343,7 @@ Run the test suite to make sure it works correctly:
 
 If you're interested in speed, you may want to build the release version instead:
 
-    $ make config RELEASE=y
+    $ ./configure --enable-release
     $ make
 
 Finally, if you want to install it globally, run
diff --git a/bench/bench.sh b/bench/bench.sh
index e4b5511..cf1ae49 100644
--- a/bench/bench.sh
+++ b/bench/bench.sh
@@ -221,7 +221,8 @@ setup() {
     fi
 
     echo "Building bfs ..."
-    as-user make -s -j"$nproc" release all
+    as-user ./configure --enable-release
+    as-user make -s -j"$nproc" all
 
     as-user mkdir -p bench/corpus
 
@@ -253,7 +254,12 @@ setup() {
                 echo "Building bfs $commit ..."
                 cd "$worktree"
                 as-user git checkout -qd "$commit" --
-                as-user make -s -j"$nproc" release
+                if [ -e configure ]; then
+                    as-user ./configure --enable-release
+                    as-user make -s -j"$nproc"
+                else
+                    as-user make -s -j"$nproc" release
+                fi
                 if [ -e ./bin/bfs ]; then
                     as-user cp ./bin/bfs "$bin/bfs-$commit"
                 else
diff --git a/config/cc.sh b/build/cc.sh
index 45d51ca..45d51ca 100755
--- a/config/cc.sh
+++ b/build/cc.sh
diff --git a/build/config.mk b/build/config.mk
new file mode 100644
index 0000000..24873ec
--- /dev/null
+++ b/build/config.mk
@@ -0,0 +1,62 @@
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Makefile that implements `./configure`
+
+include build/prelude.mk
+include build/exports.mk
+
+# All configuration steps
+config: gen/config.mk gen/config.h
+.PHONY: config
+
+# Makefile fragments generated by `./configure`
+MKS := \
+    gen/vars.mk \
+    gen/flags.mk \
+    gen/deps.mk \
+    gen/pkgs.mk
+
+# The main configuration file, which includes the others
+gen/config.mk: ${MKS}
+	${MSG} "[ GEN] $@"
+	@printf '# %s\n' "$@" >$@
+	@printf 'include %s\n' ${.ALLSRC} >>$@
+	${VCAT} gen/config.mk
+.PHONY: gen/config.mk
+
+# Saves the configurable variables
+gen/vars.mk::
+	@${MKDIR} ${@D}
+	${MSG} "[ GEN] $@"
+	@printf '# %s\n' "$@" >$@
+	@printf 'PREFIX := %s\n' "$$XPREFIX" >>$@
+	@printf 'MANDIR := %s\n' "$$XMANDIR" >>$@
+	@printf 'OS := %s\n' "$${OS:-$$(uname)}" >>$@
+	@printf 'CC := %s\n' "$$XCC" >>$@
+	@printf 'INSTALL := %s\n' "$$XINSTALL" >>$@
+	@printf 'MKDIR := %s\n' "$$XMKDIR" >>$@
+	@printf 'PKG_CONFIG := %s\n' "$$XPKG_CONFIG" >>$@
+	@printf 'RM := %s\n' "$$XRM" >>$@
+	${VCAT} $@
+
+# Sets the build flags.  This depends on vars.mk and uses a recursive make so
+# that the default flags can depend on variables like ${OS}.
+gen/flags.mk: gen/vars.mk
+	@+XMAKEFLAGS="$$MAKEFLAGS" ${MAKE} -sf build/flags.mk $@
+.PHONY: gen/flags.mk
+
+# Check for dependency generation support
+gen/deps.mk: gen/flags.mk
+	@+XMAKEFLAGS="$$MAKEFLAGS" ${MAKE} -sf build/deps.mk $@
+.PHONY: gen/deps.mk
+
+# Auto-detect dependencies and their build flags
+gen/pkgs.mk: gen/flags.mk
+	@+XMAKEFLAGS="$$MAKEFLAGS" ${MAKE} -sf build/pkgs.mk $@
+.PHONY: gen/pkgs.mk
+
+# Compile-time feature detection
+gen/config.h: gen/config.mk
+	@+XMAKEFLAGS="$$MAKEFLAGS" ${MAKE} -sf build/header.mk $@
+.PHONY: gen/config.h
diff --git a/config/cc-define.sh b/build/define-if.sh
index edb5c87..295ead8 100755
--- a/config/cc-define.sh
+++ b/build/define-if.sh
@@ -3,17 +3,18 @@
 # Copyright © Tavian Barnes <tavianator@tavianator.com>
 # SPDX-License-Identifier: 0BSD
 
-# Output a C preprocessor definition based on whether a C source file could be
-# compiled successfully
+# Output a C preprocessor definition based on whether a command succeeds
 
 set -eu
 
-SLUG="${1#config/}"
+SLUG="${1#build/}"
 SLUG="${SLUG%.c}"
-MACRO="BFS_HAS_$(printf '%s' "$SLUG" | tr 'a-z-' 'A-Z_')"
+MACRO="BFS_$(printf '%s' "$SLUG" | tr '/a-z-' '_A-Z_')"
+shift
 
-if config/cc.sh "$1"; then
+if "$@"; then
     printf '#define %s true\n' "$MACRO"
 else
     printf '#define %s false\n' "$MACRO"
+    exit 1
 fi
diff --git a/build/deps.mk b/build/deps.mk
new file mode 100644
index 0000000..3db62b6
--- /dev/null
+++ b/build/deps.mk
@@ -0,0 +1,18 @@
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Makefile that generates gen/deps.mk
+
+include build/prelude.mk
+include gen/vars.mk
+include gen/flags.mk
+include build/exports.mk
+
+gen/deps.mk::
+	${MSG} "[ GEN] $@"
+	@printf '# %s\n' "$@" >$@
+	@if build/cc.sh -MD -MP -MF /dev/null build/empty.c; then \
+	    printf 'CPPFLAGS += -MD -MP\n'; \
+	fi >>$@ 2>$@.log
+	${VCAT} $@
+	@printf -- '-include %s\n' ${OBJS:.o=.d} >>$@
diff --git a/config/empty.c b/build/empty.c
index 4fa9a5b..4fa9a5b 100644
--- a/config/empty.c
+++ b/build/empty.c
diff --git a/config/exports.mk b/build/exports.mk
index ed19134..ed19134 100644
--- a/config/exports.mk
+++ b/build/exports.mk
diff --git a/config/flags.mk b/build/flags.mk
index ee13f06..c911b22 100644
--- a/config/flags.mk
+++ b/build/flags.mk
@@ -3,8 +3,8 @@
 
 # Makefile that generates gen/flags.mk
 
-include config/prelude.mk
-include ${GEN}/vars.mk
+include build/prelude.mk
+include gen/vars.mk
 
 # Configurable flags
 CPPFLAGS ?=
@@ -29,7 +29,7 @@ export XLDLIBS=${LDLIBS}
 # Immutable flags
 export BFS_CPPFLAGS= \
     -Isrc \
-    -I${GEN} \
+    -Igen \
     -D__EXTENSIONS__ \
     -D_ATFILE_SOURCE \
     -D_BSD_SOURCE \
@@ -75,12 +75,13 @@ export TSAN_CFLAGS=${TSAN_CFLAGS,${_TSAN}}
 export UBSAN_CFLAGS=${UBSAN_CFLAGS,${_UBSAN}}
 
 SAN_CFLAGS,y := -fno-sanitize-recover=all
-NO_SAN := ${NOR,${_ASAN},${_LSAN},${_MSAN},${_TSAN},${_UBSAN}}
-SAN := ${NOT,${NO_SAN}}
+INSANE := ${NOT,${_ASAN}${_LSAN}${_MSAN}${_TSAN}${_UBSAN}}
+SAN := ${NOT,${INSANE}}
 export SAN_CFLAGS=${SAN_CFLAGS,${SAN}}
 
 # MSAN and TSAN both need all code to be instrumented
-NOLIBS ?= ${NOT,${NOR,${_MSAN},${_TSAN}}}
+YESLIBS := ${NOT,${_MSAN}${_TSAN}}
+NOLIBS ?= ${NOT,${YESLIBS}}
 export XNOLIBS=${NOLIBS}
 
 # gcov only intercepts fork()/exec() with -std=gnu*
@@ -100,14 +101,14 @@ export RELEASE_CPPFLAGS=${RELEASE_CPPFLAGS,${_RELEASE}}
 export RELEASE_CFLAGS=${RELEASE_CFLAGS,${_RELEASE}}
 
 # Set a variable
-SETVAR = printf '%s := %s\n' >>$@
+SETVAR = @printf '%s := %s\n' >>$@
 
 # Append to a variable, if non-empty
-APPEND = append() { test -z "$$2" || printf '%s += %s\n' "$$1" "$$2" >>$@; }; append
+APPEND = @append() { test -z "$$2" || printf '%s += %s\n' "$$1" "$$2" >>$@; }; append
 
-${GEN}/flags.mk::
-	${MSG} "[ GEN] ${TGT}"
-	printf '# %s\n' "${TGT}" >$@
+gen/flags.mk::
+	${MSG} "[ GEN] $@"
+	@printf '# %s\n' "$@" >$@
 	${SETVAR} CPPFLAGS "$$BFS_CPPFLAGS"
 	${APPEND} CPPFLAGS "$$TSAN_CPPFLAGS"
 	${APPEND} CPPFLAGS "$$LINT_CPPFLAGS"
@@ -131,5 +132,5 @@ ${GEN}/flags.mk::
 	${APPEND} LDLIBS "$$EXTRA_LDLIBS"
 	${APPEND} LDLIBS "$$BFS_LDLIBS"
 	${SETVAR} NOLIBS "$$XNOLIBS"
-	test "${OS}-${SAN}" != FreeBSD-y || printf 'POSTLINK = elfctl -e +noaslr $$@\n' >>$@
+	@test "${OS}-${SAN}" != FreeBSD-y || printf 'POSTLINK = elfctl -e +noaslr $$@\n' >>$@
 	${VCAT} $@
diff --git a/config/acl-get-entry.c b/build/has/acl-get-entry.c
index 3cce771..3cce771 100644
--- a/config/acl-get-entry.c
+++ b/build/has/acl-get-entry.c
diff --git a/config/acl-get-file.c b/build/has/acl-get-file.c
index 89fbf23..89fbf23 100644
--- a/config/acl-get-file.c
+++ b/build/has/acl-get-file.c
diff --git a/config/acl-get-tag-type.c b/build/has/acl-get-tag-type.c
index 2901956..2901956 100644
--- a/config/acl-get-tag-type.c
+++ b/build/has/acl-get-tag-type.c
diff --git a/config/acl-is-trivial-np.c b/build/has/acl-is-trivial-np.c
index 9ca9fc7..9ca9fc7 100644
--- a/config/acl-is-trivial-np.c
+++ b/build/has/acl-is-trivial-np.c
diff --git a/config/acl-trivial.c b/build/has/acl-trivial.c
index 7efc838..7efc838 100644
--- a/config/acl-trivial.c
+++ b/build/has/acl-trivial.c
diff --git a/config/aligned-alloc.c b/build/has/aligned-alloc.c
index 4460038..4460038 100644
--- a/config/aligned-alloc.c
+++ b/build/has/aligned-alloc.c
diff --git a/config/confstr.c b/build/has/confstr.c
index 58280b4..58280b4 100644
--- a/config/confstr.c
+++ b/build/has/confstr.c
diff --git a/config/extattr-get-file.c b/build/has/extattr-get-file.c
index ac9cf96..ac9cf96 100644
--- a/config/extattr-get-file.c
+++ b/build/has/extattr-get-file.c
diff --git a/config/extattr-get-link.c b/build/has/extattr-get-link.c
index c35be5b..c35be5b 100644
--- a/config/extattr-get-link.c
+++ b/build/has/extattr-get-link.c
diff --git a/config/extattr-list-file.c b/build/has/extattr-list-file.c
index e68a8bb..e68a8bb 100644
--- a/config/extattr-list-file.c
+++ b/build/has/extattr-list-file.c
diff --git a/config/extattr-list-link.c b/build/has/extattr-list-link.c
index 49f0ec2..49f0ec2 100644
--- a/config/extattr-list-link.c
+++ b/build/has/extattr-list-link.c
diff --git a/config/fdclosedir.c b/build/has/fdclosedir.c
index f4ad1f5..f4ad1f5 100644
--- a/config/fdclosedir.c
+++ b/build/has/fdclosedir.c
diff --git a/config/getdents.c b/build/has/getdents.c
index d0d4228..d0d4228 100644
--- a/config/getdents.c
+++ b/build/has/getdents.c
diff --git a/config/getdents64-syscall.c b/build/has/getdents64-syscall.c
index 4838c14..4838c14 100644
--- a/config/getdents64-syscall.c
+++ b/build/has/getdents64-syscall.c
diff --git a/config/getdents64.c b/build/has/getdents64.c
index 1abf36d..1abf36d 100644
--- a/config/getdents64.c
+++ b/build/has/getdents64.c
diff --git a/config/getprogname-gnu.c b/build/has/getprogname-gnu.c
index 6b97c5e..6b97c5e 100644
--- a/config/getprogname-gnu.c
+++ b/build/has/getprogname-gnu.c
diff --git a/config/getprogname.c b/build/has/getprogname.c
index 83dc8e8..83dc8e8 100644
--- a/config/getprogname.c
+++ b/build/has/getprogname.c
diff --git a/config/max-align-t.c b/build/has/max-align-t.c
index 96165ce..96165ce 100644
--- a/config/max-align-t.c
+++ b/build/has/max-align-t.c
diff --git a/config/pipe2.c b/build/has/pipe2.c
index 4cb43b5..4cb43b5 100644
--- a/config/pipe2.c
+++ b/build/has/pipe2.c
diff --git a/config/posix-spawn-addfchdir-np.c b/build/has/posix-spawn-addfchdir-np.c
index b870a53..b870a53 100644
--- a/config/posix-spawn-addfchdir-np.c
+++ b/build/has/posix-spawn-addfchdir-np.c
diff --git a/config/posix-spawn-addfchdir.c b/build/has/posix-spawn-addfchdir.c
index c52ff81..c52ff81 100644
--- a/config/posix-spawn-addfchdir.c
+++ b/build/has/posix-spawn-addfchdir.c
diff --git a/config/st-acmtim.c b/build/has/st-acmtim.c
index d687ab0..d687ab0 100644
--- a/config/st-acmtim.c
+++ b/build/has/st-acmtim.c
diff --git a/config/st-acmtimespec.c b/build/has/st-acmtimespec.c
index f747bc0..f747bc0 100644
--- a/config/st-acmtimespec.c
+++ b/build/has/st-acmtimespec.c
diff --git a/config/st-birthtim.c b/build/has/st-birthtim.c
index 4964571..4964571 100644
--- a/config/st-birthtim.c
+++ b/build/has/st-birthtim.c
diff --git a/config/st-birthtimespec.c b/build/has/st-birthtimespec.c
index 91a613f..91a613f 100644
--- a/config/st-birthtimespec.c
+++ b/build/has/st-birthtimespec.c
diff --git a/config/st-flags.c b/build/has/st-flags.c
index b1d0c32..b1d0c32 100644
--- a/config/st-flags.c
+++ b/build/has/st-flags.c
diff --git a/config/statx-syscall.c b/build/has/statx-syscall.c
index 87ec869..87ec869 100644
--- a/config/statx-syscall.c
+++ b/build/has/statx-syscall.c
diff --git a/config/statx.c b/build/has/statx.c
index 65f1674..65f1674 100644
--- a/config/statx.c
+++ b/build/has/statx.c
diff --git a/config/strerror-l.c b/build/has/strerror-l.c
index 3dcc4d7..3dcc4d7 100644
--- a/config/strerror-l.c
+++ b/build/has/strerror-l.c
diff --git a/config/strerror-r-gnu.c b/build/has/strerror-r-gnu.c
index 26ca0ee..26ca0ee 100644
--- a/config/strerror-r-gnu.c
+++ b/build/has/strerror-r-gnu.c
diff --git a/config/strerror-r-posix.c b/build/has/strerror-r-posix.c
index 41b2d30..41b2d30 100644
--- a/config/strerror-r-posix.c
+++ b/build/has/strerror-r-posix.c
diff --git a/config/tm-gmtoff.c b/build/has/tm-gmtoff.c
index 543df48..543df48 100644
--- a/config/tm-gmtoff.c
+++ b/build/has/tm-gmtoff.c
diff --git a/config/uselocale.c b/build/has/uselocale.c
index a712ff8..a712ff8 100644
--- a/config/uselocale.c
+++ b/build/has/uselocale.c
diff --git a/build/header.mk b/build/header.mk
new file mode 100644
index 0000000..a9157ad
--- /dev/null
+++ b/build/header.mk
@@ -0,0 +1,66 @@
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Makefile that generates gen/config.h
+
+include build/prelude.mk
+include gen/config.mk
+include build/exports.mk
+
+# All header fragments we generate
+HEADERS := \
+    gen/has/acl-get-entry.h \
+    gen/has/acl-get-file.h \
+    gen/has/acl-get-tag-type.h \
+    gen/has/acl-is-trivial-np.h \
+    gen/has/acl-trivial.h \
+    gen/has/aligned-alloc.h \
+    gen/has/confstr.h \
+    gen/has/extattr-get-file.h \
+    gen/has/extattr-get-link.h \
+    gen/has/extattr-list-file.h \
+    gen/has/extattr-list-link.h \
+    gen/has/fdclosedir.h \
+    gen/has/getdents.h \
+    gen/has/getdents64.h \
+    gen/has/getdents64-syscall.h \
+    gen/has/getprogname.h \
+    gen/has/getprogname-gnu.h \
+    gen/has/max-align-t.h \
+    gen/has/pipe2.h \
+    gen/has/posix-spawn-addfchdir.h \
+    gen/has/posix-spawn-addfchdir-np.h \
+    gen/has/st-acmtim.h \
+    gen/has/st-acmtimespec.h \
+    gen/has/st-birthtim.h \
+    gen/has/st-birthtimespec.h \
+    gen/has/st-flags.h \
+    gen/has/statx.h \
+    gen/has/statx-syscall.h \
+    gen/has/strerror-l.h \
+    gen/has/strerror-r-gnu.h \
+    gen/has/strerror-r-posix.h \
+    gen/has/tm-gmtoff.h \
+    gen/has/uselocale.h
+
+# Previously generated by pkgs.mk
+PKG_HEADERS := ${ALL_PKGS:%=gen/use/%.h}
+
+gen/config.h: ${PKG_HEADERS} ${HEADERS}
+	${MSG} "[ GEN] $@"
+	@printf '// %s\n' "$@" >$@
+	@printf '#ifndef BFS_CONFIG_H\n' >>$@
+	@printf '#define BFS_CONFIG_H\n' >>$@
+	@cat ${.ALLSRC} >>$@
+	@printf '#endif // BFS_CONFIG_H\n' >>$@
+	@cat ${.ALLSRC:%=%.log} >gen/config.log
+	${VCAT} $@
+.PHONY: gen/config.h
+
+# The short name of the config test
+SLUG = ${@:gen/%.h=%}
+
+${HEADERS}::
+	@${MKDIR} ${@D}
+	@build/define-if.sh ${SLUG} build/cc.sh build/${SLUG}.c >$@ 2>$@.log; \
+	    build/msg-if.sh "[ CC ] ${SLUG}.c" test $$? -eq 0
diff --git a/build/msg-if.sh b/build/msg-if.sh
new file mode 100755
index 0000000..8112aea
--- /dev/null
+++ b/build/msg-if.sh
@@ -0,0 +1,21 @@
+#!/bin/sh
+
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Print a success/failure indicator from a makefile:
+#
+#     $ ./configure
+#     [ CC ] use/liburing.c                  ✘
+#     [ CC ] use/oniguruma.c                 ✔
+
+set -eu
+
+MSG="$1"
+shift
+
+if "$@"; then
+    build/msg.sh "$(printf '%-37s  ✔' "$MSG")"
+else
+    build/msg.sh "$(printf '%-37s  ✘' "$MSG")"
+fi
diff --git a/build/msg.sh b/build/msg.sh
new file mode 100755
index 0000000..a7da31b
--- /dev/null
+++ b/build/msg.sh
@@ -0,0 +1,62 @@
+#!/bin/sh
+
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Print a message from a makefile:
+#
+#     $ make -s
+#     $ make
+#     [ CC ] src/main.c
+#     $ make V=1
+#     cc -Isrc -Igen -D...
+
+set -eu
+
+# Get the $MAKEFLAGS from the top-level make invocation
+MFLAGS="${XMAKEFLAGS-${MAKEFLAGS-}}"
+
+# Check if make should be quiet (make -s)
+is_quiet() {
+    # GNU make puts single-letter flags in the first word of $MAKEFLAGS,
+    # without a leading dash
+    case "${MFLAGS%% *}" in
+        -*) : ;;
+        *s*) return 0 ;;
+    esac
+
+    # BSD make puts each flag separately like -r -s -j 48
+    for flag in $MFLAGS; do
+        case "$flag" in
+            # Ignore things like --jobserver-auth
+            --*) continue ;;
+            # Skip variable assignments
+            *=*) break ;;
+            -*s*) return 0 ;;
+        esac
+    done
+
+    return 1
+}
+
+# Check if make should be loud (make V=1)
+is_loud() {
+    test "$XV"
+}
+
+MSG="$1"
+shift
+
+if ! is_quiet && ! is_loud; then
+    printf '%s\n' "$MSG"
+fi
+
+if [ $# -eq 0 ]; then
+    exit
+fi
+
+if is_loud; then
+    printf '%s\n' "$*"
+fi
+
+"$@"
diff --git a/config/pkgconf.sh b/build/pkgconf.sh
index 2fb2f1e..96e4bf1 100755
--- a/config/pkgconf.sh
+++ b/build/pkgconf.sh
@@ -41,7 +41,7 @@ if [ -z "$MODE" ]; then
         CFLAGS=$("$0" --cflags "$LIB") || exit 1
         LDFLAGS=$("$0" --ldflags "$LIB") || exit 1
         LDLIBS=$("$0" --ldlibs "$LIB") || exit 1
-        config/cc.sh $CFLAGS $LDFLAGS config/$LIB.c $LDLIBS || exit 1
+        build/cc.sh $CFLAGS $LDFLAGS build/use/$LIB.c $LDLIBS || exit 1
     done
 fi
 
diff --git a/build/pkgs.mk b/build/pkgs.mk
new file mode 100644
index 0000000..39b550d
--- /dev/null
+++ b/build/pkgs.mk
@@ -0,0 +1,33 @@
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# Makefile that generates gen/pkgs.mk
+
+include build/prelude.mk
+include gen/vars.mk
+include gen/flags.mk
+include build/exports.mk
+
+HEADERS := ${ALL_PKGS:%=gen/use/%.h}
+
+gen/pkgs.mk: ${HEADERS}
+	${MSG} "[ GEN] $@"
+	@printf '# %s\n' "$@" >$@
+	@gen() { \
+	    printf 'PKGS := %s\n' "$$*"; \
+	    printf 'CFLAGS += %s\n' "$$(build/pkgconf.sh --cflags "$$@")"; \
+	    printf 'LDFLAGS += %s\n' "$$(build/pkgconf.sh --ldflags "$$@")"; \
+	    printf 'LDLIBS := %s $${LDLIBS}\n' "$$(build/pkgconf.sh --ldlibs "$$@")"; \
+	}; \
+	gen $$(grep -l ' true$$' ${.ALLSRC} | sed 's|.*/\(.*\)\.h|\1|') >>$@
+	${VCAT} $@
+
+.PHONY: gen/pkgs.mk
+
+# Convert gen/use/foo.h to foo
+PKG = ${@:gen/use/%.h=%}
+
+${HEADERS}::
+	@${MKDIR} ${@D}
+	@build/define-if.sh use/${PKG} build/pkgconf.sh ${PKG} >$@ 2>$@.log; \
+	    build/msg-if.sh "[ CC ] use/${PKG}.c" test $$? -eq 0;
diff --git a/build/prelude.mk b/build/prelude.mk
new file mode 100644
index 0000000..5be26cb
--- /dev/null
+++ b/build/prelude.mk
@@ -0,0 +1,122 @@
+# 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,}      =>   [emtpy]
+#
+# 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
+
+# List all object files here, as they're needed by both `./configure` and `make`
+
+# All object files except the entry point
+LIBBFS := \
+    obj/src/alloc.o \
+    obj/src/bar.o \
+    obj/src/bfstd.o \
+    obj/src/bftw.o \
+    obj/src/color.o \
+    obj/src/ctx.o \
+    obj/src/diag.o \
+    obj/src/dir.o \
+    obj/src/dstring.o \
+    obj/src/eval.o \
+    obj/src/exec.o \
+    obj/src/expr.o \
+    obj/src/fsade.o \
+    obj/src/ioq.o \
+    obj/src/mtab.o \
+    obj/src/opt.o \
+    obj/src/parse.o \
+    obj/src/printf.o \
+    obj/src/pwcache.o \
+    obj/src/stat.o \
+    obj/src/thread.o \
+    obj/src/trie.o \
+    obj/src/typo.o \
+    obj/src/xregex.o \
+    obj/src/xspawn.o \
+    obj/src/xtime.o \
+    obj/gen/version.o
+
+# Unit test objects
+UNIT_OBJS := \
+    obj/tests/alloc.o \
+    obj/tests/bfstd.o \
+    obj/tests/bit.o \
+    obj/tests/ioq.o \
+    obj/tests/main.o \
+    obj/tests/trie.o \
+    obj/tests/xspawn.o \
+    obj/tests/xtime.o
+
+# All object files
+OBJS := \
+    obj/src/main.o \
+    obj/tests/mksock.o \
+    obj/tests/xspawnee.o \
+    obj/tests/xtouch.o \
+    ${LIBBFS} \
+    ${UNIT_OBJS}
diff --git a/config/libacl.c b/build/use/libacl.c
index de1fe50..de1fe50 100644
--- a/config/libacl.c
+++ b/build/use/libacl.c
diff --git a/config/libcap.c b/build/use/libcap.c
index 58e832c..58e832c 100644
--- a/config/libcap.c
+++ b/build/use/libcap.c
diff --git a/config/libselinux.c b/build/use/libselinux.c
index bca409d..bca409d 100644
--- a/config/libselinux.c
+++ b/build/use/libselinux.c
diff --git a/config/liburing.c b/build/use/liburing.c
index bea499a..bea499a 100644
--- a/config/liburing.c
+++ b/build/use/liburing.c
diff --git a/config/oniguruma.c b/build/use/oniguruma.c
index cb17596..cb17596 100644
--- a/config/oniguruma.c
+++ b/build/use/oniguruma.c
diff --git a/config/config.mk b/config/config.mk
deleted file mode 100644
index 280c6ac..0000000
--- a/config/config.mk
+++ /dev/null
@@ -1,63 +0,0 @@
-# Copyright © Tavian Barnes <tavianator@tavianator.com>
-# SPDX-License-Identifier: 0BSD
-
-# Makefile fragment that implements `make config`
-
-include config/prelude.mk
-include config/exports.mk
-
-# All configuration steps
-config: ${CONFIG} ${GEN}/config.h
-.PHONY: config
-
-# Makefile fragments generated by `make config`
-MKS := \
-    ${GEN}/vars.mk \
-    ${GEN}/flags.mk \
-    ${GEN}/deps.mk \
-    ${GEN}/pkgs.mk
-
-# The main configuration file, which includes the others
-${CONFIG}: ${MKS}
-	${MSG} "[ GEN] ${TGT}"
-	@printf '# %s\n' "${TGT}" >$@
-	@printf 'include $${GEN}/%s\n' ${MKS:${GEN}/%=%} >>$@
-	${VCAT} ${CONFIG}
-.PHONY: ${CONFIG}
-
-# Saves the configurable variables
-${GEN}/vars.mk::
-	@${MKDIR} ${@D}
-	${MSG} "[ GEN] ${TGT}"
-	@printf '# %s\n' "${TGT}" >$@
-	@printf 'PREFIX := %s\n' "$$XPREFIX" >>$@
-	@printf 'MANDIR := %s\n' "$$XMANDIR" >>$@
-	@printf 'OS := %s\n' "$${OS:-$$(uname)}" >>$@
-	@printf 'CC := %s\n' "$$XCC" >>$@
-	@printf 'INSTALL := %s\n' "$$XINSTALL" >>$@
-	@printf 'MKDIR := %s\n' "$$XMKDIR" >>$@
-	@printf 'PKG_CONFIG := %s\n' "$$XPKG_CONFIG" >>$@
-	@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
-
-# Auto-detect dependencies and their build flags
-${GEN}/pkgs.mk: ${GEN}/flags.mk
-	@+${MAKE} -sf config/pkgs.mk $@
-.PHONY: ${GEN}/pkgs.mk
-
-# Compile-time feature detection
-${GEN}/config.h: ${CONFIG}
-	@+${MAKE} -sf config/header.mk $@
-.PHONY: ${GEN}/config.h
diff --git a/config/deps.mk b/config/deps.mk
deleted file mode 100644
index ac394a5..0000000
--- a/config/deps.mk
+++ /dev/null
@@ -1,18 +0,0 @@
-# Copyright © Tavian Barnes <tavianator@tavianator.com>
-# SPDX-License-Identifier: 0BSD
-
-# Makefile that generates gen/deps.mk
-
-include config/prelude.mk
-include ${GEN}/vars.mk
-include ${GEN}/flags.mk
-include config/exports.mk
-
-${GEN}/deps.mk::
-	${MSG} "[ GEN] ${TGT}"
-	printf '# %s\n' "${TGT}" >$@
-	if config/cc.sh -MD -MP -MF /dev/null config/empty.c; then \
-	    printf 'DEPFLAGS = -MD -MP\n'; \
-	fi >>$@ 2>$@.log
-	${VCAT} $@
-	printf -- '-include %s\n' ${OBJS:.o=.d} >>$@
diff --git a/config/header.mk b/config/header.mk
deleted file mode 100644
index ccc36d3..0000000
--- a/config/header.mk
+++ /dev/null
@@ -1,70 +0,0 @@
-# Copyright © Tavian Barnes <tavianator@tavianator.com>
-# SPDX-License-Identifier: 0BSD
-
-# Makefile that generates gen/config.h
-
-include config/prelude.mk
-include ${GEN}/config.mk
-include config/exports.mk
-
-# All header fragments we generate
-HEADERS := \
-    ${GEN}/acl-get-entry.h \
-    ${GEN}/acl-get-file.h \
-    ${GEN}/acl-get-tag-type.h \
-    ${GEN}/acl-is-trivial-np.h \
-    ${GEN}/acl-trivial.h \
-    ${GEN}/aligned-alloc.h \
-    ${GEN}/confstr.h \
-    ${GEN}/extattr-get-file.h \
-    ${GEN}/extattr-get-link.h \
-    ${GEN}/extattr-list-file.h \
-    ${GEN}/extattr-list-link.h \
-    ${GEN}/fdclosedir.h \
-    ${GEN}/getdents.h \
-    ${GEN}/getdents64.h \
-    ${GEN}/getdents64-syscall.h \
-    ${GEN}/getprogname.h \
-    ${GEN}/getprogname-gnu.h \
-    ${GEN}/max-align-t.h \
-    ${GEN}/pipe2.h \
-    ${GEN}/posix-spawn-addfchdir.h \
-    ${GEN}/posix-spawn-addfchdir-np.h \
-    ${GEN}/st-acmtim.h \
-    ${GEN}/st-acmtimespec.h \
-    ${GEN}/st-birthtim.h \
-    ${GEN}/st-birthtimespec.h \
-    ${GEN}/st-flags.h \
-    ${GEN}/statx.h \
-    ${GEN}/statx-syscall.h \
-    ${GEN}/strerror-l.h \
-    ${GEN}/strerror-r-gnu.h \
-    ${GEN}/strerror-r-posix.h \
-    ${GEN}/tm-gmtoff.h \
-    ${GEN}/uselocale.h
-
-${GEN}/config.h: ${HEADERS}
-	${MSG} "[ GEN] ${TGT}"
-	printf '// %s\n' "${TGT}" >$@
-	printf '#ifndef BFS_CONFIG_H\n' >>$@
-	printf '#define BFS_CONFIG_H\n' >>$@
-	printf '#define BFS_USE_%s true\n' $$(printf '%s\n' ${PKGS} | tr 'a-z-' 'A-Z_') >>$@
-	cat ${.ALLSRC} >>$@
-	printf '#endif // BFS_CONFIG_H\n' >>$@
-	cat ${.ALLSRC:%=%.log} >$@.log
-	${RM} ${.ALLSRC} ${.ALLSRC:%=%.log}
-	${VCAT} $@
-.PHONY: ${GEN}/config.h
-
-# The C source file to attempt to compile
-CSRC = ${@:${GEN}/%.h=config/%.c}
-
-${HEADERS}::
-	config/cc-define.sh ${CSRC} >$@ 2>$@.log
-	if ! [ "${IS_V}" ]; then \
-	    if grep -q 'true$$' $@; then \
-	        printf '[ CC ] %-${MSG_WIDTH}s  ✔\n' ${CSRC}; \
-	    else \
-	        printf '[ CC ] %-${MSG_WIDTH}s  ✘\n' ${CSRC}; \
-	    fi; \
-	fi
diff --git a/config/pkgs.mk b/config/pkgs.mk
deleted file mode 100644
index 2c100ab..0000000
--- a/config/pkgs.mk
+++ /dev/null
@@ -1,42 +0,0 @@
-# Copyright © Tavian Barnes <tavianator@tavianator.com>
-# SPDX-License-Identifier: 0BSD
-
-# Makefile that generates gen/pkgs.mk
-
-include config/prelude.mk
-include ${GEN}/vars.mk
-include ${GEN}/flags.mk
-include config/exports.mk
-
-# External dependencies
-USE_PKGS := \
-    ${GEN}/libacl.use \
-    ${GEN}/libcap.use \
-    ${GEN}/libselinux.use \
-    ${GEN}/liburing.use \
-    ${GEN}/oniguruma.use
-
-${GEN}/pkgs.mk: ${USE_PKGS}
-	${MSG} "[ GEN] ${TGT}"
-	printf '# %s\n' "${TGT}" >$@
-	gen() { \
-	    printf 'PKGS := %s\n' "$$*"; \
-	    printf 'CFLAGS += %s\n' "$$(config/pkgconf.sh --cflags "$$@")"; \
-	    printf 'LDFLAGS += %s\n' "$$(config/pkgconf.sh --ldflags "$$@")"; \
-	    printf 'LDLIBS := %s $${LDLIBS}\n' "$$(config/pkgconf.sh --ldlibs "$$@")"; \
-	}; \
-	gen $$(cat ${.ALLSRC}) >>$@
-	${VCAT} $@
-.PHONY: ${GEN}/pkgs.mk
-
-# Convert ${GEN}/foo.use to foo
-PKG = ${@:${GEN}/%.use=%}
-
-${USE_PKGS}::
-	if config/pkgconf.sh ${PKG} 2>$@.log; then \
-	    printf '%s\n' ${PKG} >$@; \
-	    test "${IS_V}" || printf '[ CC ] %-${MSG_WIDTH}s  ✔\n' config/${PKG}.c; \
-	else \
-	    : >$@; \
-	    test "${IS_V}" || printf '[ CC ] %-${MSG_WIDTH}s  ✘\n' config/${PKG}.c; \
-	fi
diff --git a/config/prelude.mk b/config/prelude.mk
deleted file mode 100644
index e1e7a4d..0000000
--- a/config/prelude.mk
+++ /dev/null
@@ -1,170 +0,0 @@
-# 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 ?= $^
-
-# For out-of-tree builds, e.g.
-#
-#     $ make config BUILDDIR=/path/to/build/dir
-#     $ make BUILDDIR=/path/to/build/dir
-BUILDDIR ?= .
-
-# Shorthand for build subdirectories
-BIN := ${BUILDDIR}/bin
-GEN := ${BUILDDIR}/gen
-OBJ := ${BUILDDIR}/obj
-
-# GNU make strips a leading ./ from target names, so do the same for BSD make
-BIN := ${BIN:./%=%}
-GEN := ${GEN:./%=%}
-OBJ := ${OBJ:./%=%}
-
-# The configuration file generated by `make config`
-CONFIG := ${GEN}/config.mk
-
-# Installation paths
-DESTDIR ?=
-PREFIX ?= /usr
-MANDIR ?= ${PREFIX}/share/man
-
-# GNU make supports `export VAR`, but BSD make requires `export VAR=value`.
-# Sadly, GNU make gives a recursion error on `export VAR=${VAR}`.
-_BUILDDIR := ${BUILDDIR}
-export BUILDDIR=${_BUILDDIR}
-
-# Configurable executables; can be overridden with
-#
-#     $ make config CC=clang
-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,}      =>   [emtpy]
-#
-# Inspired by https://github.com/wahern/autoguess
-TRUTHY,y := y
-TRUTHY,1 := y
-
-# Boolean operators are also implemented with nested expansion
-NOT,y :=
-NOT,  := y
-
-# Support up to 5 arguments
-AND,y         := y
-AND,y,y       := y
-AND,y,y,y     := y
-AND,y,y,y,y   := y
-AND,y,y,y,y,y := y
-
-# NOR can be defined without combinatorial explosion.
-# OR is just ${NOT,${NOR,...}}
-NOR,     := y
-NOR,,    := y
-NOR,,,   := y
-NOR,,,,  := y
-NOR,,,,, := y
-
-# Normalize ${V} to either "y" or ""
-IS_V := ${TRUTHY,${V}}
-
-# Suppress output unless V=1
-Q, := @
-Q  := ${Q,${IS_V}}
-
-# The current target, with ${BUILDDIR} stripped for shorter messages
-TGT = ${@:${BUILDDIR}/%=%}
-
-# Show full commands with `make V=1`, otherwise short summaries
-MSG = @msg() { \
-          MSG="$$1"; \
-          shift; \
-          test "${IS_V}" || printf '%s\n' "$$MSG"; \
-          test "$${1:-}" || return 0; \
-          test "${IS_V}" && printf '%s\n' "$$*"; \
-          "$$@"; \
-      }; \
-      msg
-
-# Maximum width of a short message, to align the ✔/✘
-MSG_WIDTH := 33
-
-# cat a file if V=1
-VCAT,y := @cat
-VCAT,  := @:
-VCAT   := ${VCAT,${IS_V}}
-
-# List all object files here, as they're needed by both `make config` and `make`
-
-# All object files except the entry point
-LIBBFS := \
-    ${OBJ}/src/alloc.o \
-    ${OBJ}/src/bar.o \
-    ${OBJ}/src/bfstd.o \
-    ${OBJ}/src/bftw.o \
-    ${OBJ}/src/color.o \
-    ${OBJ}/src/ctx.o \
-    ${OBJ}/src/diag.o \
-    ${OBJ}/src/dir.o \
-    ${OBJ}/src/dstring.o \
-    ${OBJ}/src/eval.o \
-    ${OBJ}/src/exec.o \
-    ${OBJ}/src/expr.o \
-    ${OBJ}/src/fsade.o \
-    ${OBJ}/src/ioq.o \
-    ${OBJ}/src/mtab.o \
-    ${OBJ}/src/opt.o \
-    ${OBJ}/src/parse.o \
-    ${OBJ}/src/printf.o \
-    ${OBJ}/src/pwcache.o \
-    ${OBJ}/src/stat.o \
-    ${OBJ}/src/thread.o \
-    ${OBJ}/src/trie.o \
-    ${OBJ}/src/typo.o \
-    ${OBJ}/src/xregex.o \
-    ${OBJ}/src/xspawn.o \
-    ${OBJ}/src/xtime.o \
-    ${OBJ}/gen/version.o
-
-# Unit test objects
-UNIT_OBJS := \
-    ${OBJ}/tests/alloc.o \
-    ${OBJ}/tests/bfstd.o \
-    ${OBJ}/tests/bit.o \
-    ${OBJ}/tests/ioq.o \
-    ${OBJ}/tests/main.o \
-    ${OBJ}/tests/trie.o \
-    ${OBJ}/tests/xspawn.o \
-    ${OBJ}/tests/xtime.o
-
-# All object files
-OBJS := \
-    ${OBJ}/src/main.o \
-    ${OBJ}/tests/mksock.o \
-    ${OBJ}/tests/xspawnee.o \
-    ${OBJ}/tests/xtouch.o \
-    ${LIBBFS} \
-    ${UNIT_OBJS}
diff --git a/configure b/configure
new file mode 100755
index 0000000..d42dec3
--- /dev/null
+++ b/configure
@@ -0,0 +1,137 @@
+#!/bin/sh
+
+# Copyright © Tavian Barnes <tavianator@tavianator.com>
+# SPDX-License-Identifier: 0BSD
+
+# bfs build configuration script
+
+set -eu
+
+# Default to `make`
+MAKE="${MAKE:-make}"
+
+# Pass -j$(nproc) unless MAKEFLAGS is set
+if [ "${MAKEFLAGS+y}" ]; then
+    j=""
+else
+    j="-j$({ nproc || sysctl -n hw.ncpu || getconf _NPROCESSORS_ONLN || echo 1; } 2>/dev/null)"
+fi
+
+for arg; do
+    case "$arg" in
+        -h|--help)
+            cat <<EOF
+Usage:
+
+  \$ $0 [--enable-*|--disable-*] [CC=...] [CFLAGS=...] [...]
+  \$ $MAKE $j
+
+Variables set in the environment or on the command line will be picked up:
+
+  MAKE
+      The make implementation to use
+  CC
+      The C compiler to use
+
+  CPPFLAGS="-I... -D..."
+  CFLAGS="-W... -f..."
+  LDFLAGS="-L... -Wl,..."
+      Preprocessor/compiler/linker flags
+
+  LDLIBS="-l... -l..."
+      Dynamic libraries to link
+
+  EXTRA_{CPPFLAGS,CFLAGS,LDFLAGS,LDLIBS}
+      Adds to the default flags, instead of replacing them
+
+The default flags result in a plain debug build.  Other build profiles include:
+
+  --enable-release
+      Enable optimizations, disable assertions
+  --enable-{asan,lsan,msan,tsan,ubsan}
+      Enable sanitizers
+  --enable-gcov
+      Enable code coverage instrumentation
+
+External dependencies are auto-detected by default, but you can --enable or
+--disable them manually:
+
+  --enable-libacl      --disable-libacl
+  --enable-libcap      --disable-libcap
+  --enable-libselinux  --disable-libselinux
+  --enable-liburing    --disable-liburing
+  --enable-oniguruma   --disable-oniguruma
+
+Packaging:
+
+  --prefix=/path
+      Set the installation prefix (default: /usr)
+
+This script is a thin wrapper around a makefile-based configuration system.
+Any other arguments will be passed directly to the $MAKE invocation, e.g.
+
+  \$ $0 $j V=1
+EOF
+            exit 0
+            ;;
+
+        --enable-*|--disable-*)
+            case "$arg" in
+                --enable-*) yn=y ;;
+                --disable-*) yn=n ;;
+            esac
+
+            name="${arg#--*able-}"
+            NAME=$(printf '%s' "$name" | tr 'a-z-' 'A-Z_')
+            case "$name" in
+                libacl|libcap|libselinux|liburing|oniguruma)
+                    shift
+                    set -- "$@" "USE_$NAME=$yn"
+                    ;;
+                release|asan|lsan|msan|tsan|ubsan|lint|gcov)
+                    shift
+                    set -- "$@" "$NAME=$yn"
+                    ;;
+                *)
+                    printf 'error: Unrecognized option "%s"\n\n' "$arg" >&2
+                    printf 'Run %s --help for more information.\n' "$0" >&2
+                    exit 1
+                    ;;
+            esac
+            ;;
+
+        --prefix=*)
+            shift
+            set -- "$@" "PREFIX=${arg#*=}"
+            ;;
+
+        MAKE=*)
+            MAKE="${arg#*=}"
+            shift
+            ;;
+
+        # make flag (-j2) or variable (CC=clang)
+        -*|*=*)
+            continue
+            ;;
+
+        *)
+            printf 'error: Unrecognized option "%s"\n\n' "$arg" >&2
+            printf 'Run %s --help for more information.\n' "$0" >&2
+            exit 1
+            ;;
+    esac
+done
+
+# Get the relative path to the source tree based on how the script was run
+DIR=$(dirname -- "$0")
+
+# Set up symbolic links for out-of-tree builds
+for f in Makefile build completions docs src tests; do
+    test -e "$f" || ln -s "$DIR/$f" "$f"
+done
+
+# Set MAKEFLAGS to -j$(nproc) if it's unset
+export MAKEFLAGS="${MAKEFLAGS-$j}"
+
+$MAKE -rf build/config.mk "$@"
diff --git a/docs/BUILDING.md b/docs/BUILDING.md
index 4ed139c..cb33c51 100644
--- a/docs/BUILDING.md
+++ b/docs/BUILDING.md
@@ -1,110 +1,157 @@
 Building `bfs`
 ==============
 
-Compiling
----------
-
-`bfs` uses [GNU Make](https://www.gnu.org/software/make/) as its build system.
 A simple invocation of
 
-    $ make config
+    $ ./configure
     $ make
 
 should build `bfs` successfully.
-As usual with `make`, you can run a [parallel build](https://www.gnu.org/software/make/manual/html_node/Parallel.html) with `-j`.
-For example, to use all your cores, run `make -j$(nproc)`.
 
-### Targets
 
-| Command          | Description                                                   |
-|------------------|---------------------------------------------------------------|
-| `make config`    | Configures the build system                                   |
-| `make`           | Builds just the `bfs` binary                                  |
-| `make all`       | Builds everything, including the tests (but doesn't run them) |
-| `make check`     | Builds everything, and runs the tests                         |
-| `make install`   | Installs `bfs` (with man page, shell completions, etc.)       |
-| `make uninstall` | Uninstalls `bfs`                                              |
-| `make clean`     | Delete the build products                                     |
-| `make distclean` | Delete all generated files, including the build configuration |
+Configuration
+-------------
+
+```console
+$ ./configure --help
+Usage:
+
+  $ ./configure [--enable-*|--disable-*] [CC=...] [CFLAGS=...] [...]
+  $ make
+
+...
+```
+
+### Variables
+
+Variables set in the environment or on the command line will be picked up:
+These variables specify binaries to run during the configuration and build process:
+
+<pre>
+<b>MAKE</b>=<i>make</i>
+    <a href="https://en.wikipedia.org/wiki/Make_(software)">make</a> implementation
+<b>CC</b>=<i>cc</i>
+    C compiler
+<b>INSTALL</b>=<i>install</i>
+    Copy files during <i>make install</i>
+<b>MKDIR</b>="<i>mkdir -p</i>"
+    Create directories
+<b>PKG_CONFIG</b>=<i>pkg-config</i>
+    Detect external libraries and required build flags
+<b>RM</b>="<i>rm -f</i>"
+    Delete files
+</pre>
+
+These flags will be used by the build process:
+
+<pre>
+<b>CPPFLAGS</b>="<i>-I... -D...</i>"
+<b>CFLAGS</b>="<i>-W... -f...</i>"
+<b>LDFLAGS</b>="<i>-L... -Wl,...</i>"
+    Preprocessor/compiler/linker flags
+
+<b>LDLIBS</b>="<i>-l... -l...</i>"
+    Dynamic libraries to link
+
+<b>EXTRA_</b>{<b>CPPFLAGS</b>,<b>CFLAGS</b>,<b>LDFLAGS</b>,<b>LDLIBS</b>}="<i>...</i>"
+    Adds to the default flags, instead of replacing them
+</pre>
 
 ### Build profiles
 
-The configuration system provides a few shorthand flags for handy configurations:
-
-| Command                 | Description                                                 |
-|-------------------------|-------------------------------------------------------------|
-| `make config RELEASE=y` | Build `bfs` with optimizations, LTO, and without assertions |
-| `make config ASAN=y`    | Enable [AddressSanitizer]                                   |
-| `make config LSAN=y`    | Enable [LeakSanitizer]                                      |
-| `make config MSAN=y`    | Enable [MemorySanitizer]                                    |
-| `make config TSAN=y`    | Enable [ThreadSanitizer]                                    |
-| `make config UBSAN=y`   | Enable [UndefinedBehaviorSanitizer]                         |
-| `make config GCOV=y`    | Enable [code coverage]                                      |
-
-[AddressSanitizer]: https://github.com/google/sanitizers/wiki/AddressSanitizer
-[LeakSanitizer]: https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer#stand-alone-mode
-[MemorySanitizer]: https://github.com/google/sanitizers/wiki/MemorySanitizer
-[ThreadSanitizer]: https://github.com/google/sanitizers/wiki/ThreadSanitizerCppManual
-[UndefinedBehaviorSanitizer]: https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html
-[code coverage]: https://gcc.gnu.org/onlinedocs/gcc/Gcov.html
-
-You can combine multiple profiles (e.g. `make config ASAN=y UBSAN=y`), but not all of them will work together.
-
-### Flags
-
-Other flags can be specified on the `make config` command line or in the environment.
-Here are some of the common ones; check the [`Makefile`](/Makefile) for more.
-
-| Flag                                | Description                                        |
-|-------------------------------------|----------------------------------------------------|
-| `CC`                                | The C compiler to use, e.g. `make config CC=clang` |
-| `CFLAGS`<br>`EXTRA_CFLAGS`          | Override/add to the default compiler flags         |
-| `LDFLAGS`<br>`EXTRA_LDFLAGS`        | Override/add to the linker flags                   |
-| `USE_LIBACL`<br>`USE_LIBCAP`<br>... | Enable/disable [optional dependencies]             |
-| `TEST_FLAGS`                        | `tests.sh` flags for `make check`                  |
-| `BUILDDIR`                          | The build output directory (default: `.`)          |
-| `DESTDIR`                           | The root directory for `make install`              |
-| `PREFIX`                            | The installation prefix (default: `/usr`)          |
-| `MANDIR`                            | The man page installation directory                |
-
-[optional dependencies]: #dependencies
+The default flags result in a plain debug build.
+Other build profiles can be enabled:
+
+<pre>
+--enable-release
+    Enable optimizations, disable assertions
+
+--enable-<a href="https://github.com/google/sanitizers/wiki/AddressSanitizer">asan</a>
+--enable-<a href="https://github.com/google/sanitizers/wiki/AddressSanitizerLeakSanitizer#stand-alone-mode">lsan</a>
+--enable-<a href="https://github.com/google/sanitizers/wiki/MemorySanitizer">msan</a>
+--enable-<a href="https://github.com/google/sanitizers/wiki/ThreadSanitizerCppManual">tsan</a>
+--enable-<a href="https://clang.llvm.org/docs/UndefinedBehaviorSanitizer.html">ubsan</a>
+    Enable sanitizers
+
+--enable-<a href="https://gcc.gnu.org/onlinedocs/gcc/gcov/introduction-to-gcov.html">gcov</a>
+    Enable code coverage instrumentation
+</pre>
+
+You can combine multiple profiles (e.g. `./configure --enable-asan --enable-ubsan`), but not all of them will work together.
 
 ### Dependencies
 
 `bfs` depends on some system libraries for some of its features.
-These dependencies are optional, and can be turned off in `make config` if necessary by setting the appropriate variable to `n` (e.g. `make config USE_ONIGURUMA=n`).
+External dependencies are auto-detected by default, but you can `--enable` or `--disable` them manually:
 
-| Dependency   | Platforms  | `make config` flag |
-|--------------|------------|--------------------|
-| [libacl]     | Linux only | `USE_LIBACL`       |
-| [libcap]     | Linux only | `USE_LIBCAP`       |
-| [liburing]   | Linux only | `USE_LIBURING`     |
-| [libselinux] | Linux only | `USE_LIBSELINUX`   |
-| [Oniguruma]  | All        | `USE_ONIGURUMA`    |
+<pre>
+--enable-<a href="https://savannah.nongnu.org/projects/acl">libacl</a>      --disable-libacl
+--enable-<a href="https://sites.google.com/site/fullycapable/">libcap</a>      --disable-libcap
+--enable-<a href="https://github.com/SELinuxProject/selinux">libselinux</a>  --disable-libselinux
+--enable-<a href="https://github.com/axboe/liburing">liburing</a>    --disable-liburing
+--enable-<a href="https://github.com/kkos/oniguruma">oniguruma</a>   --disable-oniguruma
+</pre>
 
-[libacl]: https://savannah.nongnu.org/projects/acl
-[libcap]: https://sites.google.com/site/fullycapable/
-[libselinux]: https://github.com/SELinuxProject/selinux
-[liburing]: https://github.com/axboe/liburing
-[Oniguruma]: https://github.com/kkos/oniguruma
+[`pkg-config`] is used, if available, to detect these libraries and any additional build flags they may require.
+If this is undesireable, disable it by setting `PKG_CONFIG` to the empty string (`./configure PKG_CONFIG=""`).
 
-### Dependency tracking
+[`pkg-config`]: https://www.freedesktop.org/wiki/Software/pkg-config/
 
-The build system automatically tracks header dependencies with the `-M` family of compiler options (see `DEPFLAGS` in the [`Makefile`](/Makefile)).
-So if you edit a header file, `make` will rebuild the necessary object files ensuring they don't go out of sync.
+### Out-of-tree builds
 
-We also add a dependency on the current configuration, so you can change configurations and rebuild without having to `make clean`.
+You can set up an out-of-tree build by running the `configure` script from another directory, for example:
 
-We go one step further than most build systems by tracking the flags that were used for the previous compilation.
-That means you can change configurations without having to `make clean`.
-For example,
-
-    $ make config
-    $ make
-    $ make config RELEASE=y
+    $ mkdir out
+    $ cd out
+    $ ../configure
     $ make
 
-will build the project in debug mode and then rebuild it in release mode.
+
+Building
+--------
+
+### Targets
+
+The [`Makefile`](/Makefile) supports several different build targets:
+
+<pre>
+make
+    The default target; builds just the <i>bfs</i> binary
+make <b>all</b>
+    Builds everything, including the tests (but doesn't run them)
+
+make <b>check</b>
+    Builds everything, and runs all tests
+make <b>unit-tests</b>
+    Builds and runs the unit tests
+make <b>integration-tests</b>
+    Builds and runs the integration tests
+make <b>distcheck</b>
+    Builds and runs the tests in multiple different configurations
+
+make <b>install</b>
+    Installs bfs globally
+make <b>uninstall</b>
+    Uninstalls bfs
+
+make <b>clean</b>
+    Deletes all built files
+make <b>distclean</b>
+    Also deletes files generated by ./configure
+</pre>
+
+
+Troubleshooting
+---------------
+
+If the build fails or behaves unexpectedly, start by enabling verbose mode:
+
+    $ ./configure V=1
+    $ make V=1
+
+This will print the generated configuration and the exact commands that are executed.
+
+You can also check the file `gen/config.log`, which contains any errors from commands run during the configuration phase.
 
 
 Testing
diff --git a/docs/CHANGELOG.md b/docs/CHANGELOG.md
index 672c2b4..62b6480 100644
--- a/docs/CHANGELOG.md
+++ b/docs/CHANGELOG.md
@@ -1,6 +1,36 @@
 3.*
 ===
 
+3.2
+---
+
+**May 2, 2024**
+
+### New features
+
+- New `-limit N` action that quits immediately after `N` results
+
+- Implemented `-context` (from GNU find) for matching SELinux contexts ([#27](https://github.com/tavianator/bfs/issues/27))
+
+- Implemented `-printf %Z` for printing SELinux contexts
+
+### Changes
+
+- The build system has been rewritten, and there is now a configure step:
+
+      $ ./configure
+      $ make
+
+  See `./configure --help` or [docs/BUILDING.md](/docs/BUILDING.md) for more details.
+
+- Improved platform support
+  - Implemented `-acl` on Solaris/Illumos
+  - Implemented `-xattr` on DragonFly BSD
+
+### Bug fixes
+
+- Fixed some rarely-used code paths that clean up after allocation failures
+
 3.1.3
 -----
 
diff --git a/tests/util.sh b/tests/util.sh
index 7dba9fb..3969db5 100644
--- a/tests/util.sh
+++ b/tests/util.sh
@@ -12,12 +12,9 @@ _realpath() (
 )
 
 # Globals
-TESTS=$(_realpath "$TESTS")
-if [ "${BUILDDIR-}" ]; then
-    BIN=$(_realpath "$BUILDDIR/bin")
-else
-    BIN=$(_realpath "$TESTS/../bin")
-fi
+ROOT=$(_realpath "$(dirname -- "$TESTS")")
+TESTS="$ROOT/tests"
+BIN="$ROOT/bin"
 MKSOCK="$BIN/tests/mksock"
 XTOUCH="$BIN/tests/xtouch"
 UNAME=$(uname)
diff --git a/tests/xspawn.c b/tests/xspawn.c
index 7362aa5..785ea48 100644
--- a/tests/xspawn.c
+++ b/tests/xspawn.c
@@ -64,27 +64,20 @@ static bool check_use_path(bool use_posix) {
 		spawn.flags &= ~BFS_SPAWN_USE_POSIX;
 	}
 
-	const char *builddir = getenv("BUILDDIR");
-	dchar *bin = dstrprintf("%s/bin", builddir ? builddir : ".");
-	ret &= bfs_pcheck(bin, "dstrprintf()");
-	if (!ret) {
-		goto destroy;
-	}
-
-	ret &= bfs_pcheck(bfs_spawn_addopen(&spawn, 10, bin, O_RDONLY | O_DIRECTORY, 0) == 0);
+	ret &= bfs_pcheck(bfs_spawn_addopen(&spawn, 10, "bin", O_RDONLY | O_DIRECTORY, 0) == 0);
 	ret &= bfs_pcheck(bfs_spawn_adddup2(&spawn, 10, 11) == 0);
 	ret &= bfs_pcheck(bfs_spawn_addclose(&spawn, 10) == 0);
 	ret &= bfs_pcheck(bfs_spawn_addfchdir(&spawn, 11) == 0);
 	ret &= bfs_pcheck(bfs_spawn_addclose(&spawn, 11) == 0);
 	if (!ret) {
-		goto bin;
+		goto destroy;
 	}
 
 	// Check that $PATH is resolved in the parent's environment
 	char **envp;
 	ret &= bfs_pcheck(envp = envdup());
 	if (!ret) {
-		goto bin;
+		goto destroy;
 	}
 
 	// Check that $PATH is resolved after the file actions
@@ -138,8 +131,6 @@ env:
 		free(*var);
 	}
 	free(envp);
-bin:
-	dstrfree(bin);
 destroy:
 	ret &= bfs_pcheck(bfs_spawn_destroy(&spawn) == 0);
 out: