---
# System prepended metadata

title: '[Record] Utilization of make and Makefile to build a binary'

---

# [Record] Utilization of make and Makefile to build a binary
###### tags: `make`, `Makefile`, `gcc`, `hello world`, `compile`, `link`

[toc]

## Introduction
>In software development, Make is a build automation tool that builds executable programs and libraries from source code by reading files called makefiles which specify how to derive the target program. Though integrated development environments and language-specific compiler features can also be used to manage a build process, Make remains widely used, especially in Unix and Unix-like operating systems.
>
>Make can be used to manage any project where some files need to be updated automatically from others whenever the others change in addition to building programs.

This page is make and Makefile hello world to show you how to use it.

## Compile and link hello world
Write a c code named main.c as shown below.

```C 
#include <stdio.h>

int main() {
  printf("Hello, world!\n");
  return 0;
}
```
And we can **compile and link** it in linux with gcc.
```bask 
Tomas# gcc main.c
Tomas# ls -al
-rwxrwxr-x  1 tomas tomas 16696  十   8 14:01 a.out
-rw-rw-r--  1 tomas tomas    76  十   8 13:32 main.c

Tomas# ./a.out
Hello, world!
```

After compiling it, we get a a.out, and we can execute it to get the output "Hello, world!"

On the other hand, we can directly build the hello world program to the name what we like by

```bash 
Tomas# gcc -o hello main.c
Tomas# ls -al
total 52
drwxrwxr-x  2 tomas tomas  4096  十   8 14:09 .
drwxr-xr-x 26 tomas tomas  4096  十   8 14:09 ..
-rwxrwxr-x  1 tomas tomas 16696  十   8 14:01 a.out
-rwxrwxr-x  1 tomas tomas 16696  十   8 14:09 hello
-rw-rw-r--  1 tomas tomas    76  十   8 13:32 main.c
Tomas# ./hello
Hello, world!
```

The usage of gcc is shown below.

:::spoiler
```bash!
Tomas# gcc --h
Usage: gcc [options] file...
Options:
  -pass-exit-codes         Exit with highest error code from a phase.
  --help                   Display this information.
  --target-help            Display target specific command line options.
  --help={common|optimizers|params|target|warnings|[^]{joined|separate|undocumented}}[,...].
                           Display specific types of command line options.
  (Use '-v --help' to display command line options of sub-processes).
  --version                Display compiler version information.
  -dumpspecs               Display all of the built in spec strings.
  -dumpversion             Display the version of the compiler.
  -dumpmachine             Display the compiler's target processor.
  -print-search-dirs       Display the directories in the compiler's search path.
  -print-libgcc-file-name  Display the name of the compiler's companion library.
  -print-file-name=<lib>   Display the full path to library <lib>.
  -print-prog-name=<prog>  Display the full path to compiler component <prog>.
  -print-multiarch         Display the target's normalized GNU triplet, used as
                           a component in the library path.
  -print-multi-directory   Display the root directory for versions of libgcc.
  -print-multi-lib         Display the mapping between command line options and
                           multiple library search directories.
  -print-multi-os-directory Display the relative path to OS libraries.
  -print-sysroot           Display the target libraries directory.
  -print-sysroot-headers-suffix Display the sysroot suffix used to find headers.
  -Wa,<options>            Pass comma-separated <options> on to the assembler.
  -Wp,<options>            Pass comma-separated <options> on to the preprocessor.
  -Wl,<options>            Pass comma-separated <options> on to the linker.
  -Xassembler <arg>        Pass <arg> on to the assembler.
  -Xpreprocessor <arg>     Pass <arg> on to the preprocessor.
  -Xlinker <arg>           Pass <arg> on to the linker.
  -save-temps              Do not delete intermediate files.
  -save-temps=<arg>        Do not delete intermediate files.
  -no-canonical-prefixes   Do not canonicalize paths when building relative
                           prefixes to other gcc components.
  -pipe                    Use pipes rather than intermediate files.
  -time                    Time the execution of each subprocess.
  -specs=<file>            Override built-in specs with the contents of <file>.
  -std=<standard>          Assume that the input sources are for <standard>.
  --sysroot=<directory>    Use <directory> as the root directory for headers
                           and libraries.
  -B <directory>           Add <directory> to the compiler's search paths.
  -v                       Display the programs invoked by the compiler.
  -###                     Like -v but options quoted and commands not executed.
  -E                       Preprocess only; do not compile, assemble or link.
  -S                       Compile only; do not assemble or link.
  -c                       Compile and assemble, but do not link.
  -o <file>                Place the output into <file>.
  -pie                     Create a dynamically linked position independent
                           executable.
  -shared                  Create a shared library.
  -x <language>            Specify the language of the following input files.
                           Permissible languages include: c c++ assembler none
                           'none' means revert to the default behavior of
                           guessing the language based on the file's extension.

Options starting with -g, -f, -m, -O, -W, or --param are automatically
 passed on to the various sub-processes invoked by gcc.  In order to pass
 other options on to these processes the -W<letter> options must be used.

For bug reporting instructions, please see:
<file:///usr/share/doc/gcc-9/README.Bugs>.
```
:::

## Compile and link hello world manually
In a big project, it is possible to compile the source code to get many object files at one time and link them latter.

For example,
```shell
# Compiling
gcc -c x.c
gcc -c y.c
gcc -c z.c

# Linking
gcc -o mytool x.o y.o z.o
```

Here demos a simple example.
```shell 
Tomas# gcc -c main.c
Tomas# ls -al
-rw-rw-r--  1 tomas tomas  1680  十   8 14:17 main.o

Tomas# gcc -o main main.o
Tomas# ls -al
-rwxrwxr-x  1 tomas tomas 16696  十   8 14:19 main
-rw-rw-r--  1 tomas tomas    76  十   8 13:32 main.c
-rw-rw-r--  1 tomas tomas  1680  十   8 14:17 main.o

Tomas# ./main
Hello, world!
```

## Makefile hello world
Beside, we can write a simple Makefile to build the program, too.

```bash 
Tomas# vi Makefile
all:
        @echo build the hello world.
        gcc -o hello main.c

        @echo execute the hello world.
        ./hello
clean:
        @echo clean all except for the source
        rm *.o hello
```

And now, we can build it simply by "*make*".

```bash 
Tomas# make
build the hello world.
gcc -o hello main.c
execute the hello world.
./hello
Hello, world!

Tomas# ls -al
-rwxrwxr-x  1 tomas tomas 16696  十   8 14:25 hello
-rw-rw-r--  1 tomas tomas    76  十   8 13:32 main.c
-rw-rw-r--  1 tomas tomas    99  十   8 14:25 Makefile

Tomas# file hello
hello: ELF 64-bit LSB shared object, x86-64, version 1 (SYSV), dynamically linked, interpreter /lib64/ld-linux-x86-64.so.2, BuildID[sha1]=b1825aad62ec89f9b5048d7a8b5371a722ee4830, for GNU/Linux 3.2.0, not stripped

Tomas# readelf -a hello
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              DYN (Shared object file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x1060
  Start of program headers:          64 (bytes into file)
  Start of section headers:          14712 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         13
  Size of section headers:           64 (bytes)
  Number of section headers:         31
  Section header string table index: 30

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       0000000000000008  0000000000000000  WA       0     0     1
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       0000000000000202  0000000000000000           0     0     1
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Key to Flags:
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There are no section groups in this file.

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```

## Advanced Makefile with a library

Assume we are going to build an application together with a library mylib which can be a static or a dynamic library.

```shell 
#
# 'make depend' uses makedepend to automatically generate dependencies
#               (dependencies are added to end of Makefile)
# 'make'        build executable file 'mycc'
# 'make clean'  removes all .o and executable files
#

# define the C compiler to use
CC = gcc

# define any compile-time flags
CFLAGS = -Wall -g

# define any directories containing header files other than /usr/include
#
INCLUDES = -I/home/tomas/include  -I../include

# define library paths in addition to /usr/lib
#   if I wanted to include libraries not in /usr/lib I'd specify
#   their path using -Lpath, something like:
LFLAGS = -L/home/tomas/lib  -L../lib

# define any libraries to link into executable:
#   if I want to link in libraries (libx.so or libx.a) I use the -llibname
#   option, something like (this will link in libmylib.so:
LIBS = -lmylib -lm

# define the C source files
SRCS = main.c

# define the C object files
#
# This uses Suffix Replacement within a macro:
#   $(name:string1=string2)
#         For each word in 'name' replace 'string1' with 'string2'
# Below we are replacing the suffix .c of all words in the macro SRCS
# with the .o suffix
#
OBJS = $(SRCS:.c=.o)

# define the executable file
MAIN = hello

#
# The following part of the makefile is generic; it can be used to
# build any executable just by changing the definitions above and by
# deleting dependencies appended to the file from 'make depend'
#

.PHONY: depend clean

all: $(MAIN)
        @echo  Simple application named hello has been compiled

$(MAIN): $(OBJS)
        $(CC) $(CFLAGS) $(INCLUDES) -o $(MAIN) $(OBJS) $(LFLAGS) $(LIBS)

# this is a suffix replacement rule for building .o's from .c's
# it uses automatic variables $<: the name of the prerequisite of
# the rule(a .c file) and $@: the name of the target of the rule (a .o file)
# (see the gnu make manual section about automatic variables)
.c.o:
        $(CC) $(CFLAGS) $(INCLUDES) -c $<  -o $@

clean:
        $(RM) *.o *~ $(MAIN)

depend: $(SRCS)
        makedepend $(INCLUDES) $^

# DO NOT DELETE THIS LINE -- make depend needs it
```

## Reference
https://en.wikipedia.org/wiki/Make_(software)
https://blog.gtwang.org/programming/gcc-comipler-basic-tutorial-examples/
https://www.cs.swarthmore.edu/~newhall/unixhelp/howto_makefiles.html
https://hackmd.io/@TomasZheng/ByLACT1Wp