3 files changed, 14 insertions, 12 deletions
diff --git a/.gitignore b/.gitignore
index 76b7428..faa1ff5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,3 +1,2 @@
-.flags
 /build/
 /bfs
diff --git a/Makefile b/Makefile
index a6e7363..acc5cbf 100644
--- a/Makefile
+++ b/Makefile
@@ -235,18 +235,18 @@ $(BIN_GOALS):
 build build/tests:
 	$(MKDIR) $@
 
-build/%.o: src/%.c .flags | build
+build/%.o: src/%.c build/FLAGS
 	$(CC) $(ALL_CFLAGS) -c $< -o $@
 
-build/tests/%.o: tests/%.c .flags | build/tests
+build/tests/%.o: tests/%.c build/FLAGS | build/tests
 	$(CC) $(ALL_CFLAGS) -c $< -o $@
 
 # Save the full set of flags to rebuild everything when they change
-.flags: FORCE
-	@./flags.sh $(CC) : $(ALL_CFLAGS) : $(ALL_LDFLAGS) : $(ALL_LDLIBS)
+build/FLAGS: FORCE | build
+	@./flags.sh $@ $(CC) : $(ALL_CFLAGS) : $(ALL_LDFLAGS) : $(ALL_LDLIBS)
 .PHONY: FORCE
 
-# Make sure that "make release" builds everything, but "make release main.o" doesn't
+# Make sure that "make release" builds everything, but "make release build/main.o" doesn't
 $(FLAG_GOALS): $(FLAG_PREREQS)
 	@:
 .PHONY: $(FLAG_GOALS)
@@ -273,7 +273,7 @@ endif
 .PHONY: distcheck
 
 clean:
-	$(RM) -r bfs .flags build
+	$(RM) -r bfs build
 .PHONY: clean
 
 install:
diff --git a/flags.sh b/flags.sh
index 15a3a77..5711a18 100755
--- a/flags.sh
+++ b/flags.sh
@@ -1,11 +1,14 @@
 #!/usr/bin/env bash
 
-set -e
+set -eu
 
-echo "$@" >.newflags
+OUT="$1"
+shift
 
-if [ -e .flags ] && cmp -s .flags .newflags; then
-    rm .newflags
+echo "$@" >"$OUT.tmp"
+
+if [ -e "$OUT" ] && cmp -s "$OUT" "$OUT.tmp"; then
+    rm "$OUT.tmp"
 else
-    mv .newflags .flags
+    mv "$OUT.tmp" "$OUT"
 fi