Call make
command this way:
make CFLAGS=-Dvar=42
And be sure to use $(CFLAGS)
in your compile command in the Makefile. As @jørgensen mentioned , putting the variable assignment after the make
command will override the CFLAGS
value already defined the Makefile.
Alternatively you could set -Dvar=42
in another variable than CFLAGS
and then reuse this variable in CFLAGS
to avoid completely overriding CFLAGS
.