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If you just want program1 , you can run just make (it will run the first target). If you just want program2 , run make program2 . You have more control. And of course, a target all: program1 program2 will do just that (being it the first, running your 2 other targets).
It should be CFLAGS := -Wall -Wextra $(CFLAGS) , the difference is that CFLAGS is explicitly appended. So for example, you may set -Og , but user don't want optimization and passes CFLAGS=-O0 on command line. By using CFLAGS += -Og your -Og will take over the user provided value.
Try using target-specific variables. A target-specific variable is declared like this:
TARGET: VAR := foo # Any valid form of assignment may be used ( =, :=, +=, ?=)
Now when the target named TARGET is being made, the variable named VAR will have the value "foo".
Using target-specific variables, you could do this, for example:
OBJ=[all other .o files here, e.g. D.o, D.o, E.o .... Z.o]
SPECIAL_OBJS=A.o B.o
all: $(OBJ) $(SPECIAL_OBJS)
$(SPECIAL_OBJS): EXTRA_FLAGS := -std=c99 # Whatever extra flags you need
%.o: %.c
@echo [Compiling]: $<
$(CC) $(CFLAGS) $(EXTRA_FLAGS) -o $@ -c $<
The approach taken by linux kernel build system:
CFLAGS += $(CFLAGS-$@)
And then,
CFLAGS-A.o += -DEXTRA
CFLAGS-B.o += -DEXTRA
I can't answer the question for raw makefiles, but if you are willing to use automake it is trivial:
foo_CFLAGS = [options passed to CC only when building foo]
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