build-once run-anywhere c library
![Cosmopolitan Honeybadger](usr/share/img/honeybadger.png)

[![build](https://github.com/jart/cosmopolitan/actions/workflows/build.yml/badge.svg)](https://github.com/jart/cosmopolitan/actions/workflows/build.yml)
# Cosmopolitan

[Cosmopolitan Libc](https://justine.lol/cosmopolitan/index.html) makes C
a build-once run-anywhere language, like Java, except it doesn't need an
interpreter or virtual machine. Instead, it reconfigures stock GCC and
Clang to output a POSIX-approved polyglot format that runs natively on
Linux + Mac + Windows + FreeBSD + OpenBSD + NetBSD + BIOS with the best
possible performance and the tiniest footprint imaginable.

## Background

For an introduction to this project, please read the [αcτµαlly pδrταblε
εxεcµταblε](https://justine.lol/ape.html) blog post and [cosmopolitan
libc](https://justine.lol/cosmopolitan/index.html) website. We also have
[API documentation](https://justine.lol/cosmopolitan/documentation.html).

## Getting Started

If you're doing your development work on Linux or BSD then you need just
five files to get started. Here's what you do on Linux:

```sh
wget https://justine.lol/cosmopolitan/cosmopolitan-amalgamation-2.2.zip
unzip cosmopolitan-amalgamation-2.2.zip
printf 'main() { printf("hello world\\n"); }\n' >hello.c
gcc -g -Os -static -nostdlib -nostdinc -fno-pie -no-pie -mno-red-zone \
  -fno-omit-frame-pointer -pg -mnop-mcount -mno-tls-direct-seg-refs -gdwarf-4 \
  -o hello.com.dbg hello.c -fuse-ld=bfd -Wl,-T,ape.lds -Wl,--gc-sections \
  -include cosmopolitan.h crt.o ape-no-modify-self.o cosmopolitan.a
objcopy -S -O binary hello.com.dbg hello.com
```

You now have a portable program.

```sh
./hello.com
bash -c './hello.com'  # zsh/fish workaround (we patched them in 2021)
```

If `./hello.com` executed on Linux throws an error about not finding an
interpreter, it should be fixed by running the following command (although
note that it may not survive a system restart):

```sh
sudo sh -c "echo ':APE:M::MZqFpD::/bin/sh:' >/proc/sys/fs/binfmt_misc/register"
```

If the same command produces puzzling errors on WSL or WINE when using
Redbean 2.x, they may be fixed by disabling binfmt_misc:

```sh
sudo sh -c 'echo -1 >/proc/sys/fs/binfmt_misc/status'
```

Since we used the `ape-no-modify-self.o` bootloader (rather than
`ape.o`) your executable will not modify itself when it's run. What
it'll instead do, is extract a 4kb program (the [APE loader](https://justine.lol/apeloader/))
to `${TMPDIR:-${HOME:-.}}` that maps your program into memory without
needing to copy it. The APE loader must be in an executable location
(e.g. not stored on a `noexec` mount) for it to run. See below for
alternatives:

It's possible to install the APE loader systemwide as follows.

```sh
# System-Wide APE Install
# for Linux, Darwin, and BSDs
# 1. Copies APE Loader to /usr/bin/ape
# 2. Registers w/ binfmt_misc too if Linux
ape/apeinstall.sh

# System-Wide APE Uninstall
# for Linux, Darwin, and BSDs
ape/apeuninstall.sh
```

It's also possible to convert APE binaries into the system-local format
by using the `--assimilate` flag. Please note that if binfmt_misc is in
play, you'll need to unregister it temporarily before doing this, since
the assimilate feature is part of the shell script header.

```sh
$ file hello.com
hello.com: DOS/MBR boot sector
./hello.com --assimilate
$ file hello.com
hello.com: ELF 64-bit LSB executable
```

Now that you're up and running with Cosmopolitan Libc and APE, here's
some of the most important troubleshooting tools APE offers that you
should know, in case you encounter any issues:

```sh
./hello.com --strace   # log system calls to stderr
./hello.com --ftrace   # log function calls to stderr
```

Do you love tiny binaries? If so, you may not be happy with Cosmo adding
heavyweight features like tracing to your binaries by default. In that
case, you may want to consider using our build system:

```sh
make m=tiny
```

Which will cause programs such as `hello.com` and `life.com` to shrink
from 60kb in size to about 16kb. There's also a prebuilt amalgamation
online <https://justine.lol/cosmopolitan/cosmopolitan-tiny.zip> hosted
on our download page <https://justine.lol/cosmopolitan/download.html>.

### MacOS

If you're developing on MacOS you can install the GNU compiler
collection for x86_64-elf via homebrew:

```sh
brew install x86_64-elf-gcc
```

Then in the above scripts just replace `gcc` and `objcopy` with
`x86_64-elf-gcc` and `x86_64-elf-objcopy` to compile your APE binary.

### Windows

If you're developing on Windows then you need to download an
x86_64-pc-linux-gnu toolchain beforehand. See the [Compiling on
Windows](https://justine.lol/cosmopolitan/windows-compiling.html)
tutorial. It's needed because the ELF object format is what makes
universal binaries possible.

Cosmopolitan officially only builds on Linux. However, one highly
experimental (and currently broken) thing you could try, is building the
entire cosmo repository from source using the cross9 toolchain.

```
mkdir -p o/third_party
rm -rf o/third_party/gcc
wget https://justine.lol/linux-compiler-on-windows/cross9.zip
unzip cross9.zip
mv cross9 o/third_party/gcc
build/bootstrap/make.com
```

## Source Builds

Cosmopolitan can be compiled from source on any Linux distro. First, you
need to download or clone the repository.

```sh
wget https://justine.lol/cosmopolitan/cosmopolitan.tar.gz
tar xf cosmopolitan.tar.gz  # see releases page
cd cosmopolitan
```

This will build the entire repository and run all the tests:

```sh
build/bootstrap/make.com
o//examples/hello.com
find o -name \*.com | xargs ls -rShal | less
```

If you get an error running make.com then it's probably because you have
WINE installed to `binfmt_misc`. You can fix that by installing the the
APE loader as an interpreter. It'll improve build performance too!

```sh
ape/apeinstall.sh
```

Since the Cosmopolitan repository is very large, you might only want to
build a particular thing. Cosmopolitan's build config does a good job at
having minimal deterministic builds. For example, if you wanted to build
only hello.com then you could do that as follows:

```sh
build/bootstrap/make.com o//examples/hello.com
```

Sometimes it's desirable to build a subset of targets, without having to
list out each individual one. You can do that by asking make to build a
directory name. For example, if you wanted to build only the targets and
subtargets of the chibicc package including its tests, you would say:

```sh
build/bootstrap/make.com o//third_party/chibicc
o//third_party/chibicc/chibicc.com --help
```

Cosmopolitan provides a variety of build modes. For example, if you want
really tiny binaries (as small as 12kb in size) then you'd say:

```sh
build/bootstrap/make.com m=tiny
```

Here's some other build modes you can try:

```sh
build/bootstrap/make.com m=dbg       # asan + ubsan + debug
build/bootstrap/make.com m=asan      # production memory safety
build/bootstrap/make.com m=opt       # -march=native optimizations
build/bootstrap/make.com m=rel       # traditional release binaries
build/bootstrap/make.com m=optlinux  # optimal linux-only performance
build/bootstrap/make.com m=fastbuild # build 28% faster w/o debugging
build/bootstrap/make.com m=tinylinux # tiniest linux-only 4kb binaries
```

For further details, see [//build/config.mk](build/config.mk).

## GDB

Here's the recommended `~/.gdbinit` config:

```gdb
set host-charset UTF-8
set target-charset UTF-8
set target-wide-charset UTF-8
set osabi none
set complaints 0
set confirm off
set history save on
set history filename ~/.gdb_history
define asm
  layout asm
  layout reg
end
define src
  layout src
  layout reg
end
src
```

You normally run the `.com.dbg` file under gdb. If you need to debug the
`.com` file itself, then you can load the debug symbols independently as

```
gdb foo.com -ex 'add-symbol-file foo.com.dbg 0x401000'
```

## Support Vector

| Platform        | Min Version | Circa |
| :---            | ---:        | ---:  |
| AMD             | K8 Venus    | 2005  |
| Intel           | Core        | 2006  |
| Linux           | 2.6.18      | 2007  |
| Windows         | 8 [1]       | 2012  |
| Mac OS X        | 15.6        | 2018  |
| OpenBSD         | 6.4         | 2018  |
| FreeBSD         | 13          | 2020  |
| NetBSD          | 9.2         | 2021  |

[1] See our [vista branch](https://github.com/jart/cosmopolitan/tree/vista)
    for a community supported version of Cosmopolitan that works on Windows
    Vista and Windows 7.

## Special Thanks

Funding for this project is crowdsourced using
[GitHub Sponsors](https://github.com/sponsors/jart) and
[Patreon](https://www.patreon.com/jart). Your support is what makes this
project possible. Thank you! We'd also like to give special thanks to
the following groups and individuals:

- [Joe Drumgoole](https://github.com/jdrumgoole)
- [Rob Figueiredo](https://github.com/robfig)
- [Wasmer](https://wasmer.io/)

For publicly sponsoring our work at the highest tier.
