path: root/contrib/bc/README.md

# `bc`

[![Coverity Scan Build Status][17]][18]

***WARNING: This project has moved to [https://git.yzena.com/][20] for [these
reasons][21], though GitHub will remain a mirror.***

This is an implementation of the [POSIX `bc` calculator][12] that implements
[GNU `bc`][1] extensions, as well as the period (`.`) extension for the BSD
flavor of `bc`.

For more information, see this `bc`'s full manual.

This `bc` also includes an implementation of `dc` in the same binary, accessible
via a symbolic link, which implements all FreeBSD and GNU extensions. (If a
standalone `dc` binary is desired, `bc` can be copied and renamed to `dc`.) The
`!` command is omitted; I believe this poses security concerns and that such
functionality is unnecessary.

For more information, see the `dc`'s full manual.

This `bc` is Free and Open Source Software (FOSS). It is offered under the BSD
2-clause License. Full license text may be found in the [`LICENSE.md`][4] file.

## Prerequisites

This `bc` only requires a C99-compatible compiler and a (mostly) POSIX
2008-compatible system with the XSI (X/Open System Interfaces) option group.

Since POSIX 2008 with XSI requires the existence of a C99 compiler as `c99`, any
POSIX and XSI-compatible system will have everything needed.

Systems that are known to work:

* Linux
* FreeBSD
* OpenBSD
* NetBSD
* Mac OSX
* Solaris* (as long as the Solaris version supports POSIX 2008)
* AIX
* HP-UX* (except for history)

Please submit bug reports if this `bc` does not build out of the box on any
system besides Windows. If Windows binaries are needed, they can be found at
[xstatic][6].

## Build

This `bc` should build unmodified on any POSIX-compliant system.

For more complex build requirements than the ones below, see the
[build manual][5].

### Pre-built Binaries

It is possible to download pre-compiled binaries for a wide list of platforms,
including Linux- and Windows-based systems, from [xstatic][6]. This link always
points to the latest release of `bc`.

### Default

For the default build with optimization, use the following commands in the root
directory:

```
./configure.sh -O3
make
```

### One Calculator

To only build `bc`, use the following commands:

```
./configure.sh --disable-dc
make
```

To only build `dc`, use the following commands:

```
./configure.sh --disable-bc
make
```

### Debug

For debug builds, use the following commands in the root directory:

```
./configure.sh -g
make
```

### Install

To install, use the following command:

```
make install
```

By default, `bc` and `dc` will be installed in `/usr/local`. For installing in
other locations, use the `PREFIX` environment variable when running
`configure.sh` or pass the `--prefix=<prefix>` option to `configure.sh`. See the
[build manual][5], or run `./configure.sh --help`, for more details.

### Library

This `bc` does provide a way to build a math library with C bindings. This is
done by the `-a` or `--library` options to `configure.sh`:

```
./configure.sh -a
```

When building the library, the executables are not built. For more information,
see the [build manual][5].

The library API can be found in [`manuals/bcl.3.md`][26] or `man bcl` once the
library is installed.

The library is built as `bin/libbcl.a`.

### Package and Distro Maintainers

#### Recommended Compiler

When I ran benchmarks with my `bc` compiled under `clang`, it performed much
better than when compiled under `gcc`. I recommend compiling this `bc` with
`clang`.

I also recommend building this `bc` with C11 if you can because `bc` will detect
a C11 compiler and add `_Noreturn` to any relevant function(s).

#### Recommended Optimizations

I wrote this `bc` with Separation of Concerns, which means that there are many
small functions that could be inlined. However, they are often called across
file boundaries, and the default optimizer can only look at the current file,
which means that they are not inlined.

Thus, because of the way this `bc` is built, it will automatically be slower
than other `bc` implementations when running scripts with no math. (My `bc`'s
math is *much* faster, so any non-trivial script should run faster in my `bc`.)

Some, or all, of the difference can be made up with the right optimizations. The
optimizations I recommend are:

1.	`-O3`
2.	`-flto` (link-time optimization)

in that order.

Link-time optimization, in particular, speeds up the `bc` a lot. This is because
when link-time optimization is turned on, the optimizer can look across files
and inline *much* more heavily.

However, I recommend ***NOT*** using `-march=native`. Doing so will reduce this
`bc`'s performance, at least when building with link-time optimization. See the
[benchmarks][19] for more details.

#### Stripping Binaries

By default, non-debug binaries are stripped, but stripping can be disabled with
the `-T` option to `configure.sh`.

#### Using This `bc` as an Alternative

If this `bc` is packaged as an alternative to an already existing `bc` package,
it is possible to rename it in the build to prevent name collision. To prepend
to the name, just run the following:

```
EXECPREFIX=<some_prefix> ./configure.sh
```

To append to the name, just run the following:

```
EXECSUFFIX=<some_suffix> ./configure.sh
```

If a package maintainer wishes to add both a prefix and a suffix, that is
allowed.

**Note**: The suggested name (and package name) when `bc` is not available is
`bc-gh`.

#### Karatsuba Number

Package and distro maintainers have one tool at their disposal to build this
`bc` in the optimal configuration: `karatsuba.py`.

This script is not a compile-time or runtime prerequisite; it is for package and
distro maintainers to run once when a package is being created. It finds the
optimal Karatsuba number (see the [algorithms manual][7] for more information)
for the machine that it is running on.

The easiest way to run this script is with `make karatsuba`.

If desired, maintainers can also skip running this script because there is a
sane default for the Karatsuba number.

## Status

This `bc` is robust.

It is well-tested, fuzzed, and fully standards-compliant (though not certified)
with POSIX `bc`. The math has been tested with 40+ million random problems, so
it is as correct as I can make it.

This `bc` can be used as a drop-in replacement for any existing `bc`. This `bc`
is also compatible with MinGW toolchains, though history is not supported on
Windows.

In addition, this `bc` is considered complete; i.e., there will be no more
releases with additional features. However, it *is* actively maintained, so if
any bugs are found, they will be fixed in new releases. Also, additional
translations will also be added as they are provided.

## Comparison to GNU `bc`

This `bc` compares favorably to GNU `bc`.

* It has more extensions, which make this `bc` more useful for scripting.
* This `bc` is a bit more POSIX compliant.
* It has a much less buggy parser. The GNU `bc` will give parse errors for what
  is actually valid `bc` code, or should be. For example, putting an `else` on
  a new line after a brace can cause GNU `bc` to give a parse error.
* This `bc` has fewer crashes.
* GNU `bc` calculates the wrong number of significant digits for `length(x)`.
* GNU `bc` will sometimes print numbers incorrectly. For example, when running
  it on the file `tests/bc/power.txt` in this repo, GNU `bc` gets all the right
  answers, but it fails to wrap the numbers at the proper place when outputting
  to a file.
* This `bc` is faster. (See [Performance](#performance).)

### Performance

Because this `bc` packs more than `1` decimal digit per hardware integer, this
`bc` is faster than GNU `bc` and can be *much* faster. Full benchmarks can be
found at [manuals/benchmarks.md][19].

There is one instance where this `bc` is slower: if scripts are light on math.
This is because this `bc`'s intepreter is slightly slower than GNU `bc`, but
that is because it is more robust. See the [benchmarks][19].

## Algorithms

To see what algorithms this `bc` uses, see the [algorithms manual][7].

## Locales

Currently, this `bc` only has support for English (and US English), French,
German, Portuguese, Dutch, Polish, Russian, Japanese, and Chinese locales.
Patches are welcome for translations; use the existing `*.msg` files in
`locales/` as a starting point.

In addition, patches for improvements are welcome; the last two messages in
Portuguese were made with Google Translate, and the Dutch, Polish, Russian,
Japanese, and Chinese locales were all generated with [DeepL][22].

The message files provided assume that locales apply to all regions where a
language is used, but this might not be true for, e.g., `fr_CA` and `fr_CH`.
Any corrections or a confirmation that the current texts are acceptable for
those regions would be appreciated, too.

## Other Projects

Other projects based on this bc are:

* [busybox `bc`][8]. The busybox maintainers have made their own changes, so any
  bugs in the busybox `bc` should be reported to them.

* [toybox `bc`][9]. The maintainer has also made his own changes, so bugs in the
  toybox `bc` should be reported there.

* [FreeBSD `bc`][23]. While the `bc` in FreeBSD is kept up-to-date, it is better
  to [report bugs there][24], as well as [submit patches][25], and the
  maintainers of the package will contact me if necessary.

## Language

This `bc` is written in pure ISO C99, using POSIX 2008 APIs.

## Commit Messages

This `bc` uses the commit message guidelines laid out in [this blog post][10].

## Semantic Versioning

This `bc` uses [semantic versioning][11].

## Contents

Items labeled with `(maintainer use only)` are not included in release source
tarballs.

Files:

	.gitignore           The git ignore file (maintainer use only).
	configure            A symlink to configure.sh to make packaging easier.
	configure.sh         The configure script.
	functions.sh         A script with functions used by other scripts.
	install.sh           Install script.
	karatsuba.py         Script to find the optimal Karatsuba number.
	LICENSE.md           A Markdown form of the BSD 2-clause License.
	link.sh              A script to link dc to bc.
	locale_install.sh    A script to install locales, if desired.
	locale_uninstall.sh  A script to uninstall locales.
	Makefile.in          The Makefile template.
	manpage.sh           Script to generate man pages from markdown files.
	NOTICE.md            List of contributors and copyright owners.
	RELEASE.md           A checklist for making a release (maintainer use only).
	release.sh           A script to test for release (maintainer use only).
	safe-install.sh      Safe install script from musl libc.

Folders:

	gen      The bc math library, help texts, and code to generate C source.
	include  All header files.
	locales  Locale files, in .msg format. Patches welcome for translations.
	manuals  Manuals for both programs.
	src      All source code.
	tests    All tests.

[1]: https://www.gnu.org/software/bc/
[4]: ./LICENSE.md
[5]: ./manuals/build.md
[6]: https://pkg.musl.cc/bc/
[7]: ./manuals/algorithms.md
[8]: https://git.busybox.net/busybox/tree/miscutils/bc.c
[9]: https://github.com/landley/toybox/blob/master/toys/pending/bc.c
[10]: http://tbaggery.com/2008/04/19/a-note-about-git-commit-messages.html
[11]: http://semver.org/
[12]: https://pubs.opengroup.org/onlinepubs/9699919799/utilities/bc.html
[17]: https://img.shields.io/coverity/scan/16609.svg
[18]: https://scan.coverity.com/projects/gavinhoward-bc
[19]: ./manuals/benchmarks.md
[20]: https://git.yzena.com/gavin/bc
[21]: https://gavinhoward.com/2020/04/i-am-moving-away-from-github/
[22]: https://www.deepl.com/translator
[23]: https://svnweb.freebsd.org/base/head/contrib/bc/
[24]: https://bugs.freebsd.org/
[25]: https://reviews.freebsd.org/
[26]: ./manuals/bcl.3.md