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This is a [C11] compiler using [QBE] as a backend. It is released under
the [ISC] license.

Several GNU C [extensions] are also implemented.

There is still much to do, but it currently implements most of the
language and is capable of [building software] including itself, mcpp,
gcc 4.7, binutils, and more.

It was inspired by several other small C compilers including [8cc],
[c], [lacc], and [scc].

## Requirements

The compiler itself is written in standard C11 and can be built with
any conforming C11 compiler.

The POSIX driver depends on POSIX.1-2008 interfaces, and the `Makefile`
requires a POSIX-compatible make(1).

At runtime, you will need QBE, an assembler, and a linker for the
target system. Currently, my personal [QBE branch] is recommended, since
it may address some issues that have not yet made it upstream. Since
the preprocessor is not yet implemented, an external one is currently
required as well.

## Supported targets

All architectures supported by QBE should work (currently x86\_64 and
aarch64).

The following targets are tested by the continuous build and known to
bootstrap and pass all tests:

- `x86_64-linux-musl`
- `x86_64-linux-gnu`
- `x86_64-freebsd`
- `aarch64-linux-musl`
- `aarch64-linux-gnu`

## Building

Run `./configure` to create a `config.h` and `config.mk` appropriate for
your system. If your system is not supported by the configure script,
you can create these files manually. `config.h` should define several
string arrays (`static char *[]`):

- **`startfiles`**: Objects to pass to the linker at the beginning of
  the link command.
- **`endfiles`**: Objects to pass to the linker at the end of the link
  command (including libc).
- **`preprocesscmd`**: The preprocessor command, and any necessary flags
  for the target system.
- **`codegencmd`**: The QBE command, and possibly explicit target flags.
- **`assemblecmd`**: The assembler command.
- **`linkcmd`**: The linker command.

You may also want to customize your environment or `config.mk` with the
appropriate `CC`, `CFLAGS` and `LDFLAGS`.

If you don't have QBE installed, you can build it from the included
submodule (NOTE: BSD users will need to use gmake here), then add it to
your PATH so that the driver will be able to run it.

	make qbe
	PATH=$PWD/qbe/obj:$PATH

Once this is done, you can build with

	make

### Bootstrap

The `Makefile` includes several other targets that can be used for
bootstrapping. These targets require the ability to run the tools
specified in `config.h`.

- **`stage2`**: Build the compiler with the initial (`stage1`) output.
- **`stage3`**: Build the compiler with the `stage2` output.
- **`bootstrap`**: Build the `stage2` and `stage3` compilers, and verify
  that they are byte-wise identical.

## What's missing

- Digraph and trigraph sequences ([6.4.6p3] and [5.2.1.1], will not
  be implemented).
- Wide string literals and character constants ([#35] and [#36]).
- Variable-length arrays ([#1]).
- `volatile`-qualified types ([#7]).
- `_Thread_local` storage-class specifier ([#5]).
- `long double` type ([#3]).
- Inline assembly ([#5]).
- Preprocessor ([#6]).
- Generation of position independent code (i.e. shared libraries,
  modules, PIEs).

## Issue tracker

Please report any issues to https://todo.sr.ht/~mcf/cc-issues.

## Contributing

Send patches to me (address in commit log), or pull-requests on the
[GitHub mirror]. Once I decide on a project name, a mailing list will
be created, which will then become the preferred form of contribution.

[QBE]: https://c9x.me/compile/
[C11]: http://port70.net/~nsz/c/c11/n1570.html
[ISC]: https://git.sr.ht/~mcf/cc/blob/master/LICENSE
[extensions]: https://man.sr.ht/~mcf/cc/doc/extensions.md
[building software]: https://man.sr.ht/~mcf/cc/doc/software.md
[8cc]: https://github.com/rui314/8cc
[c]: https://github.com/andrewchambers/c
[lacc]: https://github.com/larmel/lacc
[scc]: http://www.simple-cc.org/
[QBE branch]: https://git.sr.ht/~mcf/qbe
[5.2.1.1]: http://port70.net/~nsz/c/c11/n1570.html#5.2.1.1
[6.4.6p3]: http://port70.net/~nsz/c/c11/n1570.html#6.4.6p3
[#1]: https://todo.sr.ht/~mcf/cc-issues/1
[#3]: https://todo.sr.ht/~mcf/cc-issues/3
[#5]: https://todo.sr.ht/~mcf/cc-issues/5
[#6]: https://todo.sr.ht/~mcf/cc-issues/6
[#7]: https://todo.sr.ht/~mcf/cc-issues/7
[#35]: https://todo.sr.ht/~mcf/cc-issues/35
[#36]: https://todo.sr.ht/~mcf/cc-issues/36
[#44]: https://todo.sr.ht/~mcf/cc-issues/44
[GitHub mirror]: https://github.com/michaelforney/cc