Makefile Terminology Glossary

I. Terminology Analysis

1. Automatic Variables

$<: All dependencies, e.g., fs.c, pipe.c. Expands to the first prerequisite in the dependency list.

$@: All files corresponding to the rule's target. Expands to the target filename of the current rule. Note: $(OBJECTS) refers to the collection of all targets.

$?:

$^: Expands to the entire list of prerequisites (removing all duplicate filenames).

The @ expands to the target filename of the current rule, < expands to the first prerequisite in the dependency list (e.g., for foo.o : foo.c foo.h bar.h, < represents foo.c), and ^ expands to the entire list of prerequisites (removing all duplicate filenames). Using these variables, we can write the above makefile as:

===   makefile   Start   === OBJS   =   foo.o   bar.o CC   =   gcc CFLAGS   =   -Wall   -O   -g  myprog   :   $(OBJS)     $(CC)   $^   -o   $@              // Here, $^ represents the entire list of prerequisites, which are foo.c, bar.c (implicit rule)??? $@ represents myprog, right? foo.o   :   foo.c   foo.h   bar.h     $(CC)   $(CFLAGS)   -c   $ <   -o   $@        // $< represents foo.c, $@ represents foo.o bar.o   :   bar.c   bar.h     $(CC)   $(CFLAGS)   -c   $ <   -o   $@ ===   makefile   End   ===

2. Keywords

wildcard:

Comparison: objects = *.o // Does not expand

objects := $(wildcard *.o) // Expands. Makes objects a collection of all .o files.

foreach n

3. Phony Targets: .PHONY, clean, all

all : $(OUTDIR)/$(OUTBINNAME) .PHONY : all

===============================Friendly Reminder: Phony Targets=======================================

all : prog1 prog2 prog3 .PHONY : all prog1 : prog1.o utils.o  cc -o prog1 prog1.o utils.o prog2 : prog2.o  cc -o prog2 prog2.o prog3 : prog3.o sort.o utils.o  cc -o prog3 prog3.o sort.o utils.o

====================================================================================

3. Label

4. .PHONY : clean // Indicates that clean is a phony target file

5. Environment Variable MAKEFILES: It is recommended not to use it, as it is similar to a global variable and will affect all your Makefiles. If your makefile behaves strangely, you can check if it exists in your environment variables.

II. Variable Definition

Variables here are like macro definitions in C language.

#Method 1: Define multi-line variablesdefine variablevaluevalueendef#Method 2:variable = value#Method 3:variable := value#Method 4:variable += value#Method 5:variable ?= value

III. Wildcards

...

Note: If a filename contains *, you can add an escape character \*.

=========== Example Analysis ==============

Are *.c and %.c synonymous?

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IV. Using Functions

1. $(subst ,,)

Replaces from with to in the string text.

2. $(patsubst ,,)

Pattern string substitution function: pattern

Example: $(patsubst %.c,%.o,x.c.c bar.c) replaces %.c with %.o in x.c.c bar.c. The result is x.c.o bar.o.

V. Others

1. File Search

VPATH = src:../headers

The above command specifies two directories, 'src' and '../headers'. Of course, the current directory is always searched first. Directories are separated by ':'.

   vpath %.c foo    vpath %.c blish    vpath %.c bar

The above commands indicate that .c files are first searched in the foo directory, then sequentially in the blish directory, and then the bar directory.

vpath %.h ../headers

The above is pattern search.

VI. Makefile Rules

target ... : prerequisites ... command

target: is a target file, which can be an object file (multiple files), an executable file, or a label.

prerequisites: are the files or targets required to generate target.

====================== Friendly Reminder ===============================

edit : main.o kbd.o command.o display.o insert.o search.o files.o utils.o  cc -o edit main.o kbd.o command.o display.o  insert.o search.o files.o utils.o             // Carefully observe and compare: here `cc` is followed by `-o`, then `edit`, `main.o`, etc. Below, `cc` is followed by `-c`, then `.c`.main.o : main.c defs.h  cc -c main.c

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VII. Let make Deduce Automatically

As long as makefile sees a .o file, it will automatically deduce and find the corresponding .c file to generate it.

Automatic deduction of files and their dependent commands.