Makefile only compiling the first item of list

I have this Makefile:

SRCS = ../compilation-test2/src/test2.c ./test.c
OBJS = $(foreach src,$(SRCS),$(patsubst %.c,build/%.o,$(notdir $(src))))

define build_obj
$(info $(1))
obj_file := $(patsubst %.c, build/%.o, $(notdir $(1)))
src_file := $(1)
$(info $(obj_file))
$(info $(src_file))
$(obj_file): $(src_file)
	g++ -c $(src_file) -o $(obj_file)
endef


$(foreach src,$(SRCS),$(eval $(call build_obj,$(src))))


all: $(OBJS)
	g++ $^ -o build/exec_file

clean:
	rm -rf build/*

and this directories structures:

$ tree compilation-test
compilation-test
├── Makefile
├── build
└── test.c

1 directory, 2 files
andre:~
$ tree compilation-test2/
compilation-test2/
├── include
│   └── test2.h
└── src
    └── test2.c

When I execute make only test2.c is compiled:

andre:~/compilation-test
$ make
../compilation-test2/src/test2.c


./test.c
build/test2.o
../compilation-test2/src/test2.c
g++ -c ../compilation-test2/src/test2.c -o build/test2.o
andre:~/compilation-test
$ ls build/
test2.o

Why is test.c not compiled?

When you run make without specifying any targets, it will build the first target in the makefile.

And the first target of your makefile is for one of your source files, to create its object file. So that's the only thing that will be built.

Quick solution: Move the all target to be the first target, and that should be the default.

On another note, you don't really need most of your makefile. You definitely don't need that function you define. Use the implicit rules already existing to build programs. You don't need to provide any commands to build the object files or the linking, only provide the flags through variables.

Your makefile could be simplified to:

CFLAGS = -Wall -Wextra

.PHONY: default
default: all

.PHONY: all
all: build/exec_file

build/exec_file: build/test2.o build/test.o

.PHONY: clean
clean:
    -rm -f build/*

build/test2.o: ../compilation-test2/src/test2.c

build/test.o: test.c

I've added a "default" target to be placed as the first rule in the makefile, which will then be the default target if none is specified. I also marked it and the all and clean targets as phony because they don't generate any files themselves.

I also added some default compiler flags, which will add some extra warnings when you build. This is generally a good habit, and also shows you how to add flags when needed.

And of course please take some time to read the full documentation to learn more about make and how it works.