How to write Makefile for debugging only one header and source in c

The lib folder contains many *.h and *.c files, and all files are in development phrase and they contain many errors including syntax errors. So I want to write the Makefile to debug all libraries one by one.

Here is the project folder structure (All *.c files contain the "main" function for testing purpose):

./Makefile

./src/lib/hello.h
./src/lib/hello.c
./src/lib/world.h
./src/lib/world.c
./src/lib/foo.h
./src/lib/foo.c
./src/lib/bar.h
./src/lib/bar.c

Here is the Makefile_hello for debugging "hello.h" and "hello.c":

CC = gcc
CFLAGS = -Wall -g
# How to include only "hello.h"?
INCLUDES = -Isrc/lilb
# How to write the rest for debugging only "hello.c"?

Here is the Makefile_world for debugging "world.h" and "world.c":

CC = gcc
CFLAGS = -Wall -g
# How to include only "world.h"?
INCLUDES = -Isrc/lilb
# How to write the rest for debugging only "world.c"?

How to write the correct Makefile?

Solution

# ==========================================================
#   Makefile for Modular C Project with Debug Selector
#   Usage:
#     make                → build all modules (debug)
#     make lib=foo        → build only foo.c / foo.h
#     make mode=release   → build all in release mode
#     make clean          → remove build artifacts
# ==========================================================

# Compiler and flags
CC       := gcc
MODE     ?= debug
CFLAGS   := -Wall -std=c17
INCLUDES := -Isrc/lib
BUILD    := build

ifeq ($(MODE),debug)
  CFLAGS += -g -O0
else
  CFLAGS += -O2 -DNDEBUG
endif

# Source discovery
SRC_DIR  := src/lib
SRC_ALL  := $(wildcard $(SRC_DIR)/*.c)
OBJ_ALL  := $(patsubst $(SRC_DIR)/%.c,$(BUILD)/%.o,$(SRC_ALL))
EXE      := app

# Optional single library
LIB      ?=

ifeq ($(LIB),)
  SRC := $(SRC_ALL)
  OBJ := $(OBJ_ALL)
  TARGET := $(EXE)
else
  SRC := $(SRC_DIR)/$(LIB).c
  OBJ := $(BUILD)/$(LIB).o
  TARGET := $(BUILD)/$(LIB)_test
endif

# Build rules
.PHONY: all clean dirs

all: dirs $(TARGET)

dirs:
    @mkdir -p $(BUILD)

$(EXE): $(OBJ)
    $(CC) $(CFLAGS) $(INCLUDES) -o $@ $^

$(BUILD)/%.o: $(SRC_DIR)/%.c $(SRC_DIR)/%.h
    $(CC) $(CFLAGS) $(INCLUDES) -c $< -o $@

$(BUILD)/%_test: $(BUILD)/%.o
    $(CC) $(CFLAGS) $(INCLUDES) -o $@ $^

clean:
    rm -rf $(BUILD) $(EXE)