Why does ```CFLAGS:=$(CFLAGS) -O3``` not work as expected?

Question

Makefile like this:

CFLAGS := $(CFLAGS) -O3

test: main.o
        gcc $(CFLAGS) -o $@ $^

clean:
        rm test *.o -f

compile 1: command: make, output: gcc -O3 -o test main.c

compile 2: command: make CFLAGS="-Wall -Werror", output: gcc -Wall -Werror -o test main.c

question: why not output: gcc -Wall -Werror -O3 -o test main.c ?

I see this writing in minizip: https://github.com/madler/zlib/commit/2014a993addbc8f1b9785d97f55fd189792c2f78 — minchai, Jul 08 '22 at 09:50
maybe you need [`override`](https://www.gnu.org/software/make/manual/make.html#Override-Directive) here, see this answer: https://stackoverflow.com/a/2826178/3985859 — Karsten Koop, Jul 08 '22 at 09:55

score 0 · Answer 1 · answered Jul 11 '22 at 07:43

0

use override directive:

override CFLAGS := $(CFLAGS) -O3

or

override CFLAGS += -O3

answered Jul 11 '22 at 07:43

minchai

1 Answers1