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libkernaux/README.md

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libkernaux
==========
[![Build Status](https://travis-ci.org/kernelmq/libkernaux.svg?branch=master)](https://travis-ci.org/kernelmq/libkernaux)
Auxiliary library for kernel development.
Table of contents
-----------------
* [Overview](#libkernaux)
* [Table of contents](#table-of-contents)
* [API](#api)
* [Tips](#tips)
* [Discussion](#discussion)
API
---
* [Simple command line parser](/include/kernaux/cmdline.h) *(work in progress)*
* [Multiboot 2 (GRUB 2) information parser](/include/kernaux/multiboot2.h)
* [Serial console](/include/kernaux/console.h)
* [Page Frame Allocator](/include/kernaux/pfa.h) *(work in progress)*
* ELF utils *(planned)*
* [Architecture-specific helpers](/include/kernaux/arch/)
* [printf replacement](/include/kernaux/printf.h) *(work in progress)*
* [stdlib replacement](/include/kernaux/stdlib.h):
* `memset`
* `strlen`
* `strncpy`
* `itoa` *(work in progress)*
Tips
----
Create configuration script with `./autogen.sh`.
Configure with cross-compiler in `$PATH` to make without it in `$PATH`:
```
./configure \
--host=x86-elf \
AR="$(which x86-elf-ar)" \
CC="$(which x86-elf-gcc)" \
RANLIB="$(which x86-elf-ranlib)" \
CFLAGS='-ffreestanding -nostdlib -fno-builtin -fno-stack-protector'
```
When configuring with cross-compiler you can see the following messages. It's
[a bug](https://savannah.gnu.org/support/index.php?110393) in **autoconf**, just
ignore it.
```
checking for _Bool... no
checking stddef.h usability... no
checking stddef.h presence... yes
configure: WARNING: stddef.h: present but cannot be compiled
configure: WARNING: stddef.h: check for missing prerequisite headers?
configure: WARNING: stddef.h: see the Autoconf documentation
configure: WARNING: stddef.h: section "Present But Cannot Be Compiled"
configure: WARNING: stddef.h: proceeding with the compiler's result
configure: WARNING: ## ------------------------------------------------------------ ##
configure: WARNING: ## Report this to https://github.com/kernelmq/libkernaux/issues ##
configure: WARNING: ## ------------------------------------------------------------ ##
checking for stddef.h... no
```
To install into specific directory use full path:
`DESTDIR="$(pwd)/dest" make install` instead of `DESTDIR=dest make install`.
When configured with cross-compiler, library can't be build and installed with
just `make && sudo make install`. Instead use the following commands:
* `make libkernaux.a`
* `sudo make install-exec`
* `sudo make install-data`
Check if compilation targets x86: `objdump -d src/arch/x86.o`. It should
output something like this:
```
src/arch/x86.o: file format elf32-i386
Disassembly of section .text:
00000000 <kernaux_arch_x86_hang>:
0: fa cli
1: f4 hlt
2: eb fc jmp 0 <kernaux_arch_x86_hang>
00000004 <kernaux_arch_x86_read_cr0>:
4: 0f 20 c0 mov %cr0,%eax
7: c3 ret
00000008 <kernaux_arch_x86_read_cr4>:
8: 0f 20 e0 mov %cr4,%eax
b: c3 ret
0000000c <kernaux_arch_x86_write_cr0>:
c: 8b 44 24 04 mov 0x4(%esp),%eax
10: 0f 22 c0 mov %eax,%cr0
13: c3 ret
00000014 <kernaux_arch_x86_write_cr3>:
14: 8b 44 24 04 mov 0x4(%esp),%eax
18: 0f 22 d8 mov %eax,%cr3
1b: c3 ret
0000001c <kernaux_arch_x86_write_cr4>:
1c: 8b 44 24 04 mov 0x4(%esp),%eax
20: 0f 22 e0 mov %eax,%cr4
23: c3 ret
```
Discussion
----------
* [Topic on OSDev.org forum](https://forum.osdev.org/viewtopic.php?f=1&t=37958)
* [Thread on r/osdev](https://www.reddit.com/r/osdev/comments/k3ueeu/libkernaux_auxiliary_library_for_kernel/)