Make-File: compile multiple SRC-Folders to single OBJ-Folder - c

Question

I got a project hierarchy that looks like this:
+Makefile
+---src
| main.c
| ...
| +---block
| | air.c
| | ...
| |
| +---entity
| | esc.c
| | esc.h
| | ...
| |
| \---world
| \---gen
| noise.c
| ...
| xyz.c
| ...
\---obj
main.o
air.o
esc.o
noise.o
xyz.o
...
I want to compile all the .c files in the hierarchy into one obj folder using make.
So far I got:
UNAME_S = $(shell uname -s)
CC = clang
CFLAGS = -std=c11 -O3 -g -Wall -Wextra -Wpedantic -Wstrict-aliasing
CFLAGS += -Wno-pointer-arith -Wno-newline-eof -Wno-unused-parameter -Wno-gnu-statement-expression
CFLAGS += -Wno-gnu-compound-literal-initializer -Wno-gnu-zero-variadic-macro-arguments
CFLAGS += -Ilib/cglm/include -Ilib/glad/include -Ilib/glfw/include -Ilib/stb -Ilib/noise -fbracket-depth=1024
LDFLAGS = lib/glad/src/glad.o lib/cglm/libcglm.a lib/glfw/src/libglfw3.a lib/noise/libnoise.a -lm
# GLFW required frameworks on OSX
ifeq ($(UNAME_S), Darwin)
LDFLAGS += -framework OpenGL -framework IOKit -framework CoreVideo -framework Cocoa
endif
ifeq ($(UNAME_S), Linux)
LDFLAGS += -ldl -lpthread
endif
OBJ_DIR = obj
SRC = $(wildcard src/**/*.c) $(wildcard src/*.c) $(wildcard src/**/**/*.c) $(wildcard src/**/**/**/*.c)
OBJ = $(addprefix $(OBJ_DIR)/,$(addsuffix .o,$(notdir $(basename $(SRC)))))
SRC_DIRS = $(sort $(dir $(SRC)))
BIN = bin
.PHONY: all clean
all: dirs libs game
libs:
cd lib/cglm && cmake . -DCGLM_STATIC=ON && make
cd lib/glad && $(CC) -o src/glad.o -Iinclude -c src/glad.c
cd lib/glfw && cmake . && make
cd lib/noise && make
dirs:
mkdir -p ./$(BIN) ./$(OBJ_DIR)
run: all
$(BIN)/game
game: $(OBJ)
$(CC) -o $(BIN)/game $^ $(LDFLAGS)
$(OBJ_DIR)/%.o: src/%.c
$(CC) -o $# -c $< $(CFLAGS)
$(OBJ_DIR)/%.o: src/block/%.c
$(CC) -o $# -c $< $(CFLAGS)
$(OBJ_DIR)/%.o: src/entity/%.c
$(CC) -o $# -c $< $(CFLAGS)
$(OBJ_DIR)/%.o: src/gfx/%.c
$(CC) -o $# -c $< $(CFLAGS)
$(OBJ_DIR)/%.o: src/ui/%.c
$(CC) -o $# -c $< $(CFLAGS)
$(OBJ_DIR)/%.o: src/util/%.c
$(CC) -o $# -c $< $(CFLAGS)
$(OBJ_DIR)/%.o: src/world/%.c
$(CC) -o $# -c $< $(CFLAGS)
$(OBJ_DIR)/%.o: src/world/gen/%.c
$(CC) -o $# -c $< $(CFLAGS)
clean:
rm -rf $(BIN) $(OBJ_DIR)
Is there any way to get this done in a more efficient way? Especially the $(OBJ_DIR)/%.o cases?
Variable $(SRC_DIRS) stores all src folders
Variable $(SRC) stores all .c files with their paths
Variable $(OBJ) stores all .o file paths and names

Answer 1

The best way to do this is using VPATH.
For example:
SRC := $(wildcard src/*/*.c) $(wildcard src/*.c) $(wildcard src/*/*/*.c) $(wildcard src/*/*/*/*.c)
OBJ := $(addprefix $(OBJ_DIR)/,$(addsuffix .o,$(notdir $(basename $(SRC)))))
SRC_DIRS := $(sort $(dir $(SRC)))
VPATH := $(SRC_DIRS)
...
$(OBJ_DIR)/%.o: %.c
$(CC) -o $# -c $< $(CFLAGS)
You just need the one pattern rule.