build: Simplify flags.mk

1 files changed, 43 insertions, 64 deletions

diff --git a/build/flags.mk b/build/flags.mk
index fa793b8..c50b077 100644
--- a/build/flags.mk
+++ b/build/flags.mk
@@ -6,28 +6,8 @@
 include build/prelude.mk
 include gen/vars.mk
 
-# Configurable flags
-CPPFLAGS ?=
-CFLAGS ?= \
-    -g \
-    -Wall \
-    -Wformat=2 \
-    -Werror=implicit \
-    -Wimplicit-fallthrough \
-    -Wmissing-declarations \
-    -Wshadow \
-    -Wsign-compare \
-    -Wstrict-prototypes
-LDFLAGS ?=
-LDLIBS ?=
-
-export XCPPFLAGS=${CPPFLAGS}
-export XCFLAGS=${CFLAGS}
-export XLDFLAGS=${LDFLAGS}
-export XLDLIBS=${LDLIBS}
-
-# Immutable flags
-export BFS_CPPFLAGS= \
+# Internal flags
+_CPPFLAGS := \
     -Isrc \
     -Igen \
     -D__EXTENSIONS__ \
@@ -39,14 +19,17 @@ export BFS_CPPFLAGS= \
     -D_POSIX_PTHREAD_SEMANTICS \
     -D_FILE_OFFSET_BITS=64 \
     -D_TIME_BITS=64
-export BFS_CFLAGS= -std=c17 -pthread
+
+_CFLAGS := -std=c17 -pthread
+_LDFLAGS :=
+_LDLIBS :=
 
 # Platform-specific system libraries
 LDLIBS,DragonFly := -lposix1e
 LDLIBS,Linux := -lrt
 LDLIBS,NetBSD := -lutil
 LDLIBS,SunOS := -lsec -lsocket -lnsl
-export BFS_LDLIBS=${LDLIBS,${OS}}
+_LDLIBS += ${LDLIBS,${OS}}
 
 # Build profiles
 _ASAN := ${TRUTHY,${ASAN}}
@@ -60,7 +43,7 @@ _RELEASE := ${TRUTHY,${RELEASE}}
 
 # https://github.com/google/sanitizers/issues/342
 TSAN_CPPFLAGS,y := -DBFS_USE_TARGET_CLONES=0
-export TSAN_CPPFLAGS=${TSAN_CPPFLAGS,${_TSAN}}
+_CPPFLAGS += ${TSAN_CPPFLAGS,${_TSAN}}
 
 ASAN_CFLAGS,y := -fsanitize=address
 LSAN_CFLAGS,y := -fsanitize=leak
@@ -68,69 +51,65 @@ MSAN_CFLAGS,y := -fsanitize=memory -fsanitize-memory-track-origins
 TSAN_CFLAGS,y := -fsanitize=thread
 UBSAN_CFLAGS,y := -fsanitize=undefined
 
-export ASAN_CFLAGS=${ASAN_CFLAGS,${_ASAN}}
-export LSAN_CFLAGS=${LSAN_CFLAGS,${_LSAN}}
-export MSAN_CFLAGS=${MSAN_CFLAGS,${_MSAN}}
-export TSAN_CFLAGS=${TSAN_CFLAGS,${_TSAN}}
-export UBSAN_CFLAGS=${UBSAN_CFLAGS,${_UBSAN}}
+_CFLAGS += ${ASAN_CFLAGS,${_ASAN}}
+_CFLAGS += ${LSAN_CFLAGS,${_LSAN}}
+_CFLAGS += ${MSAN_CFLAGS,${_MSAN}}
+_CFLAGS += ${TSAN_CFLAGS,${_TSAN}}
+_CFLAGS += ${UBSAN_CFLAGS,${_UBSAN}}
 
 SAN_CFLAGS,y := -fno-sanitize-recover=all
 INSANE := ${NOT,${_ASAN}${_LSAN}${_MSAN}${_TSAN}${_UBSAN}}
 SAN := ${NOT,${INSANE}}
-export SAN_CFLAGS=${SAN_CFLAGS,${SAN}}
+_CFLAGS += ${SAN_CFLAGS,${SAN}}
 
 # MSAN and TSAN both need all code to be instrumented
 YESLIBS := ${NOT,${_MSAN}${_TSAN}}
 NOLIBS ?= ${NOT,${YESLIBS}}
-export XNOLIBS=${NOLIBS}
 
 # gcov only intercepts fork()/exec() with -std=gnu*
 GCOV_CFLAGS,y := -std=gnu17 --coverage
-export GCOV_CFLAGS=${GCOV_CFLAGS,${_GCOV}}
+_CFLAGS += ${GCOV_CFLAGS,${_GCOV}}
 
 LINT_CPPFLAGS,y := -D_FORTIFY_SOURCE=3 -DBFS_LINT
 LINT_CFLAGS,y := -Werror -O2
 
-export LINT_CPPFLAGS=${LINT_CPPFLAGS,${_LINT}}
-export LINT_CFLAGS=${LINT_CFLAGS,${_LINT}}
+_CPPFLAGS += ${LINT_CPPFLAGS,${_LINT}}
+_CFLAGS += ${LINT_CFLAGS,${_LINT}}
 
 RELEASE_CPPFLAGS,y := -DNDEBUG
 RELEASE_CFLAGS,y := -O3 -flto=auto
 
-export RELEASE_CPPFLAGS=${RELEASE_CPPFLAGS,${_RELEASE}}
-export RELEASE_CFLAGS=${RELEASE_CFLAGS,${_RELEASE}}
+_CPPFLAGS += ${RELEASE_CPPFLAGS,${_RELEASE}}
+_CFLAGS += ${RELEASE_CFLAGS,${_RELEASE}}
+
+# Configurable flags
+CFLAGS ?= \
+    -g \
+    -Wall \
+    -Wformat=2 \
+    -Werror=implicit \
+    -Wimplicit-fallthrough \
+    -Wmissing-declarations \
+    -Wshadow \
+    -Wsign-compare \
+    -Wstrict-prototypes
 
-# Set a variable
-SETVAR = @printf '%s := %s\n' >>$@
+# Add the configurable flags last so they can override ours
+_CPPFLAGS += ${CPPFLAGS} ${EXTRA_CPPFLAGS}
+_CFLAGS += ${CFLAGS} ${EXTRA_CFLAGS}
+_LDFLAGS += ${LDFLAGS} ${EXTRA_LDFLAGS}
+# (except LDLIBS, as earlier libs override later ones)
+_LDLIBS := ${LDLIBS} ${EXTRA_LDLIBS} ${_LDLIBS}
 
-# Append to a variable, if non-empty
-APPEND = @append() { test -z "$$2" || printf '%s += %s\n' "$$1" "$$2" >>$@; }; append
+include build/exports.mk
 
 gen/flags.mk::
 	${MSG} "[ GEN] $@"
 	@printf '# %s\n' "$@" >$@
-	${SETVAR} _CPPFLAGS "$$BFS_CPPFLAGS"
-	${APPEND} _CPPFLAGS "$$TSAN_CPPFLAGS"
-	${APPEND} _CPPFLAGS "$$LINT_CPPFLAGS"
-	${APPEND} _CPPFLAGS "$$RELEASE_CPPFLAGS"
-	${APPEND} _CPPFLAGS "$$XCPPFLAGS"
-	${APPEND} _CPPFLAGS "$$EXTRA_CPPFLAGS"
-	${SETVAR} _CFLAGS "$$BFS_CFLAGS"
-	${APPEND} _CFLAGS "$$ASAN_CFLAGS"
-	${APPEND} _CFLAGS "$$LSAN_CFLAGS"
-	${APPEND} _CFLAGS "$$MSAN_CFLAGS"
-	${APPEND} _CFLAGS "$$TSAN_CFLAGS"
-	${APPEND} _CFLAGS "$$UBSAN_CFLAGS"
-	${APPEND} _CFLAGS "$$SAN_CFLAGS"
-	${APPEND} _CFLAGS "$$GCOV_CFLAGS"
-	${APPEND} _CFLAGS "$$LINT_CFLAGS"
-	${APPEND} _CFLAGS "$$RELEASE_CFLAGS"
-	${APPEND} _CFLAGS "$$XCFLAGS"
-	${APPEND} _CFLAGS "$$EXTRA_CFLAGS"
-	${SETVAR} _LDFLAGS "$$XLDFLAGS"
-	${SETVAR} _LDLIBS "$$XLDLIBS"
-	${APPEND} _LDLIBS "$$EXTRA_LDLIBS"
-	${APPEND} _LDLIBS "$$BFS_LDLIBS"
-	${SETVAR} NOLIBS "$$XNOLIBS"
+	@printf '_CPPFLAGS := %s\n' "$$XCPPFLAGS" >>$@
+	@printf '_CFLAGS := %s\n' "$$XCFLAGS" >>$@
+	@printf '_LDFLAGS := %s\n' "$$XLDFLAGS" >>$@
+	@printf '_LDLIBS := %s\n' "$$XLDLIBS" >>$@
+	@printf 'NOLIBS := %s\n' "$$XNOLIBS" >>$@
 	@test "${OS}-${SAN}" != FreeBSD-y || printf 'POSTLINK = elfctl -e +noaslr $$@\n' >>$@
 	${VCAT} $@