Write a Makefile to compile the .c files in each directory into their respective .o files

The process of writing a Makefile is as follows:

1. Define variables: Define variables such as compiler and compilation options.
2. Define target file: Define the target file name.
3. Define source files: Define all source files.
4. Define rules: Define the rules for compiling each source file into an object file.
5. Define pseudo-target: Defines a pseudo-target that cleans up object files and other intermediate files.

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The following is an example Makefile, assuming that each directory has a .csource file ending in that needs to be compiled into a corresponding .ofile:

CC = gcc
CFLAGS = -Wall -Wextra -Werror
SRCDIR = src
OBJDIR = obj
TARGET = myapp

SOURCES := $(wildcard $(SRCDIR)/**/*.c)
OBJECTS := $(patsubst $(SRCDIR)/%.c, $(OBJDIR)/%.o, $(SOURCES))

$(TARGET): $(OBJECTS)
	$(CC) $(CFLAGS) $^ -o $@

$(OBJDIR)/%.o: $(SRCDIR)/%.c
	$(CC) $(CFLAGS) -c $< -o $@

.PHONY: clean
clean:
	rm -rf $(OBJDIR)/*.o $(TARGET)

• CC Defines the compiler used, gcc is used here.
• CFLAGS Compilation options are defined, and some warning options are enabled here.
• SRCDIR Defines the directory where the source files are located.
• OBJDIR Defines the directory where the intermediate and object files are located.
• TARGET Defines the final generated executable file name.
• SOURCES is a list of all source files, using wildcards to recursively find source files in subdirectories. **
• OBJECTS is a list of all object files, using the patsubst function to replace the source file path with the object file path.
• $(TARGET): $(OBJECTS) Indicates that the target file depends on all intermediate files, and $ make myappthe final executable file can be generated by entering on the command line.
• $(OBJDIR)/%.o: $(SRCDIR)/%.cIndicates a rule, compiles all files in a directory into corresponding files, and stores them in the directory. $(SRCDIR) .c .o$(OBJDIR)
• .PHONY: clean Indicates that clean is a pseudo-target, not a real file, and $ make cleanall intermediate and target files can be deleted by typing in the command line.