Awesome 42

A collection of the best ressources for your 42 school journey. Please feel free to fork it / contribute to it.

Index

• Ressources
  • Subjects
  • Automated tests
• How to make a perfect correction / project
• Useful code snippets
• Good practices

Ressources

Subjects

• PDF
  • Binary-Hackers

Automated tests

• 42 File Checker ❤️: Fillit / Libft / LibftASM / Get_next_line / Ft_ls / Ft_printf / Minishell
• @jtoty: Libft
• @mguillau42 : Nm-otool

Automated code formating

I created an uncrustify config file for the 42 norm. Uncrustify allows you to format automatically your .c and ,h files. It's not complete yet, feel free to contribute to it 🙏.

Tricks

• Simulate linux efficiently on MacOS

A complete correction basics

On the newly cloned project

• cat -e auteur must show the login followed by a \n (print as $ with cat -e).
• norminette | grep 'Error' should print nothing.
• cat */*.c | grep "By: " should print the student login (it can print marvin@42.fr for the mail).

The makefile

• should have the basic rules: all , $(NAME), clean, fclean and re.
• should clean the entire project with fclean .
• should compile with -Werror -Wextra -Wall.
• should not have any *.
• should compile only modified files using .o temporary object files.

No cheating

• nm -u <exec | lib.a> should print the allowed functions for the subject. Take into account only the functions starting with one _.
• In case other functions are used for bonuses, it must be justified (for example, printf for laziness is not allowed).

No crash

• malloc return should be secure. Don't forget to check for libft return too (ft_strnew() for example).

• malloc should not leak. Each malloc must match with a free, see why here.

• However, no need to free the entire program when you use exit() on an error.

• You can use valgrind --leak-check=full <./ft_exec> to search leaks. In case the program outputs data, you can redirect valgrind output with --log-fd=9 9>>val.log.

• Check for double free.

• open , read return should be secure (returns -1 for errors). When opening or reading, you should test with folders and not allowed files (chmod 000).

• open must be followed by close.

• mmap return must be secure.

  ptr = mmap(0, buf.st_size, PROT_READ | PROT_WRITE, MAP_PRIVATE, fd, 0)) == MAP_FAILEDCheck for leaks
  

Other

• When implementing existing methods, check their prototype matches exactly.
• When implementing existing commands, check it diplays the exact same return. Use diff <(./ft_x) <(x)
• Check if globals are allowed. Use nm <./ft_x> to display them.
• Check your overflows.
• When the program expects arguments, check with empty strings.
• For executables, create a usage message.

Useful code snippets

Save flags

typedef enum	e_flag {
	FLAG_N = 1 << 0, // 0b00000001
	FLAG_R = 1 << 1, // 0b00000010
	FLAG_G = 1 << 2, // 0b00000100
}				t_flag;

// Use uint_64t for more than 8 flags
int flags = 0;              // flags = 0b00000000

// Activate the flag N
flags |= FLAG_N             // flags = 0b00000001

// Compare it with
if (flags & FLAG_N) // TRUE
    ...

Round x to a multiple of y

int x = (x + (y-1)) & ~(y-1);

Good practices

Project file structure

/project
  /inc # Put all your includes here (from libs + src)
  /libs # Put you libft + other already made projects
  /src
  Makefile # Will call the makefile of libs
  auteur

Code

• Use static on local functions and const for constants variables.
• Describe exported functions using comments
• Print errors in the FD error
• Don't use if (ptr) free(ptr), it does it for you.
• Stop thinking the norm is bad, 25 lines per function will make you code better and generic functions
• Use real variable / function names 😢
• You can use makefile -j18 for compiling using multithread.