An implementation of Unix dc and POSIX bc with GNU and BSD extensions. Finished, but well-maintained.
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20 KiB

Build

This bc attempts to be as portable as possible. It can be built on any POSIX-compliant system.

To accomplish that, a POSIX-compatible, custom configure.sh script is used to select build options, compiler, and compiler flags and generate a Makefile.

The general form of configuring, building, and installing this bc is as follows:

[ENVIRONMENT_VARIABLE=<value>...] ./configure.sh [build_options...]
make
make install

To get all of the options, including any useful environment variables, use either one of the following commands:

./configure.sh -h
./configure.sh --help

WARNING: even though configure.sh supports both option types, short and long, it does not support handling both at the same time. Use only one type.

To learn the available make targets run the following command after running the configure.sh script:

make help

See Build Environment Variables for a more detailed description of all accepted environment variables and Build Options for more detail about all accepted build options.

Cross Compiling

To cross-compile this bc, an appropriate compiler must be present and assigned to the environment variable HOSTCC or HOST_CC (the two are equivalent, though HOSTCC is prioritized). This is in order to bootstrap core file(s), if the architectures are not compatible (i.e., unlike i686 on x86_64). Thus, the approach is:

HOSTCC="/path/to/native/compiler" ./configure.sh
make
make install

HOST_CC will work in exactly the same way.

HOSTCFLAGS and HOST_CFLAGS can be used to set compiler flags for HOSTCC. (The two are equivalent, as HOSTCC and HOST_CC are.) HOSTCFLAGS is prioritized over HOST_CFLAGS. If neither are present, HOSTCC (or HOST_CC) uses CFLAGS (see Build Environment Variables for more details).

It is expected that CC produces code for the target system and HOSTCC produces code for the host system. See Build Environment Variables for more details.

If an emulator is necessary to run the bootstrap binaries, it can be set with the environment variable GEN_EMU.

Build Environment Variables

This bc supports CC, HOSTCC, HOST_CC, CFLAGS, HOSTCFLAGS, HOST_CFLAGS, CPPFLAGS, LDFLAGS, LDLIBS, PREFIX, DESTDIR, BINDIR, DATAROOTDIR, DATADIR, MANDIR, MAN1DIR, LOCALEDIR EXECSUFFIX, EXECPREFIX, LONG_BIT, GEN_HOST, and GEN_EMU environment variables in configure.sh. Any values of those variables given to configure.sh will be put into the generated Makefile.

More detail on what those environment variables do can be found in the following sections.

CC

C compiler for the target system. CC must be compatible with POSIX c99 behavior and options. However, I encourage users to use any C99 or C11 compatible compiler they wish.

If there is a space in the basename of the compiler, the items after the first space are assumed to be compiler flags, and in that case, the flags are automatically moved into CFLAGS.

Defaults to c99.

HOSTCC or HOST_CC

C compiler for the host system, used only in cross compiling. Must be compatible with POSIX c99 behavior and options.

If there is a space in the basename of the compiler, the items after the first space are assumed to be compiler flags, and in that case, the flags are automatically moved into HOSTCFLAGS.

Defaults to $CC.

CFLAGS

Command-line flags that will be passed verbatim to CC.

Defaults to empty.

HOSTCFLAGS or HOST_CFLAGS

Command-line flags that will be passed verbatim to HOSTCC or HOST_CC.

Defaults to $CFLAGS.

CPPFLAGS

Command-line flags for the C preprocessor. These are also passed verbatim to both compilers (CC and HOSTCC); they are supported just for legacy reasons.

Defaults to empty.

LDFLAGS

Command-line flags for the linker. These are also passed verbatim to both compilers (CC and HOSTCC); they are supported just for legacy reasons.

Defaults to empty.

LDLIBS

Libraries to link to. These are also passed verbatim to both compilers (CC and HOSTCC); they are supported just for legacy reasons and for cross compiling with different C standard libraries (like musl).

Defaults to empty.

PREFIX

The prefix to install to.

Can be overridden by passing the --prefix option to configure.sh.

Defaults to /usr/local.

DESTDIR

Path to prepend onto PREFIX. This is mostly for distro and package maintainers.

This can be passed either to configure.sh or make install. If it is passed to both, the one given to configure.sh takes precedence.

Defaults to empty.

BINDIR

The directory to install binaries in.

Can be overridden by passing the --bindir option to configure.sh.

Defaults to $PREFIX/bin.

INCLUDEDIR

The directory to install header files in.

Can be overridden by passing the --includedir option to configure.sh.

Defaults to $PREFIX/include.

LIBDIR

The directory to install libraries in.

Can be overridden by passing the --libdir option to configure.sh.

Defaults to $PREFIX/lib.

DATAROOTDIR

The root directory to install data files in.

Can be overridden by passing the --datarootdir option to configure.sh.

Defaults to $PREFIX/share.

DATADIR

The directory to install data files in.

Can be overridden by passing the --datadir option to configure.sh.

Defaults to $DATAROOTDIR.

MANDIR

The directory to install manpages in.

Can be overridden by passing the --mandir option to configure.sh.

Defaults to $DATADIR/man

MAN1DIR

The directory to install Section 1 manpages in. Because both bc and dc are Section 1 commands, this is the only relevant section directory.

Can be overridden by passing the --man1dir option to configure.sh.

Defaults to $MANDIR/man1.

LOCALEDIR

The directory to install locales in.

Can be overridden by passing the --localedir option to configure.sh.

Defaults to $DATAROOTDIR/locale.

EXECSUFFIX

The suffix to append onto the executable names when installing. This is for packagers and distro maintainers who want this bc as an option, but do not want to replace the default bc.

Defaults to empty.

EXECPREFIX

The prefix to append onto the executable names when building and installing. This is for packagers and distro maintainers who want this bc as an option, but do not want to replace the default bc.

Defaults to empty.

LONG_BIT

The number of bits in a C long type. This is mostly for the embedded space.

This bc uses longs internally for overflow checking. In C99, a long is required to be 32 bits. For this reason, on 8-bit and 16-bit microcontrollers, the generated code to do math with long types may be inefficient.

For most normal desktop systems, setting this is unnecessary, except that 32-bit platforms with 64-bit longs may want to set it to 32.

Defaults to the default value of LONG_BIT for the target platform. For compliance with the bc spec, the minimum allowed value is 32.

It is an error if the specified value is greater than the default value of LONG_BIT for the target platform.

GEN_HOST

Whether to use gen/strgen.c, instead of gen/strgen.sh, to produce the C files that contain the help texts as well as the math libraries. By default, gen/strgen.c is used, compiled by $HOSTCC and run on the host machine. Using gen/strgen.sh removes the need to compile and run an executable on the host machine since gen/strgen.sh is a POSIX shell script. However, gen/lib2.bc is perilously close to 4095 characters, the max supported length of a string literal in C99 (and it could be added to in the future), and gen/strgen.sh generates a string literal instead of an array, as gen/strgen.c does. For most production-ready compilers, this limit probably is not enforced, but it could be. Both options are still available for this reason.

If you are sure your compiler does not have the limit and do not want to compile and run a binary on the host machine, set this variable to "0". Any other value, or a non-existent value, will cause the build system to compile and run gen/strgen.c.

Default is "".

GEN_EMU

The emulator to run bootstrap binaries under. This is only if the binaries produced by HOSTCC (or HOST_CC) need to be run under an emulator to work.

Defaults to empty.

Build Options

This bc comes with several build options, all of which are enabled by default.

All options can be used with each other, with a few exceptions that will be noted below.

NOTE: All long options with mandatory argumenst accept either one of the following forms:

--option arg
--option=arg

Library

To build the math library, use the following commands for the configure step:

./configure.sh -a
./configure.sh --library

Both commands are equivalent.

When the library is built, history, prompt, and locales are disabled, and the functionality for bc and dc are both enabled, though the executables are not built. This is because the library's options clash with the executables.

To build an optimized version of the library, users can pass optimization options to configure.sh or include them in CFLAGS.

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

The library is built as bin/libbcl.a.

bc Only

To build bc only (no dc), use any one of the following commands for the configure step:

./configure.sh -b
./configure.sh --bc-only
./configure.sh -D
./configure.sh --disable-dc

Those commands are all equivalent.

Warning: It is an error to use those options if bc has also been disabled (see below).

dc Only

To build dc only (no bc), use either one of the following commands for the configure step:

./configure.sh -d
./configure.sh --dc-only
./configure.sh -B
./configure.sh --disable-bc

Those commands are all equivalent.

Warning: It is an error to use those options if dc has also been disabled (see above).

History

To disable signal handling, pass either the -H flag or the --disable-history option to configure.sh, as follows:

./configure.sh -H
./configure.sh --disable-history

Both commands are equivalent.

History is automatically disabled when building for Windows or on another platform that does not support the terminal handling that is required.

WARNING: Of all of the code in the bc, this is the only code that is not completely portable. If the bc does not work on your platform, your first step should be to retry with history disabled.

NLS (Locale Support)

To disable locale support (use only English), pass either the -N flag or the --disable-nls option to configure.sh, as follows:

./configure.sh -N
./configure.sh --disable-nls

Both commands are equivalent.

NLS (locale support) is automatically disabled when building for Windows or on another platform that does not support the POSIX locale API or utilities.

Prompt

By default, bc and dc print a prompt when in interactive mode. They both have the command-line option -P/--no-prompt, which turns that off, but it can be disabled permanently in the build by passing the -P flag or the --disable-prompt option to configure.sh, as follows:

./configure.sh -P
./configure.sh --disable-prompt

Both commands are equivalent.

Locales

By default, bc and dc do not install all locales, but only the enabled locales. If DESTDIR exists and is not empty, then they will install all of the locales that exist on the system. The -l flag or --install-all-locales option skips all of that and just installs all of the locales that bc and dc have, regardless. To enable that behavior, you can pass the -l flag or the --install-all-locales option to configure.sh, as follows:

./configure.sh -l
./configure.sh --install-all-locales

Both commands are equivalent.

Extra Math

This bc has 7 extra operators:

  • $ (truncation to integer)
  • @ (set precision)
  • @= (set precision and assign)
  • << (shift number left, shifts radix right)
  • <<= (shift number left and assign)
  • >> (shift number right, shifts radix left)
  • >>= (shift number right and assign)

There is no assignment version of $ because it is a unary operator.

The assignment versions of the above operators are not available in dc, but the others are, as the operators $, @, H, and h, respectively.

In addition, this bc has the option of outputting in scientific notation or engineering notation. It can also take input in scientific or engineering notation. On top of that, it has a pseudo-random number generator. (See the full manual for more details.)

Extra operators, scientific notation, engineering notation, and the pseudo-random number generator can be disabled by passing either the -E flag or the --disable-extra-math option to configure.sh, as follows:

./configure.sh -E
./configure.sh --disable-extra-math

Both commands are equivalent.

This bc also has a larger library that is only enabled if extra operators and the pseudo-random number generator are. More information about the functions can be found in the Extended Library section of the full manual.

Manpages

To disable installing manpages, pass either the -M flag or the --disable-man-pages option to configure.sh as follows:

./configure.sh -M
./configure.sh --disable-man-pages

Both commands are equivalent.

Karatsuba Length

The Karatsuba length is the point at which bc and dc switch from Karatsuba multiplication to brute force, O(n^2) multiplication. It can be set by passing the -k flag or the --karatsuba-len option to configure.sh as follows:

./configure.sh -k64
./configure.sh --karatsuba-len 64

Both commands are equivalent.

Default is 64.

WARNING: The Karatsuba Length must be a integer greater than or equal to 16 (to prevent stack overflow). If it is not, configure.sh will give an error.

Install Options

The relevant autotools-style install options are supported in configure.sh:

  • --prefix
  • --bindir
  • --datarootdir
  • --datadir
  • --mandir
  • --man1dir
  • --localedir

An example is:

./configure.sh --prefix=/usr --localedir /usr/share/nls
make
make install

They correspond to the environment variables $PREFIX, $BINDIR, $DATAROOTDIR, $DATADIR, $MANDIR, $MAN1DIR, and $LOCALEDIR, respectively.

WARNING: If the option is given, the value of the corresponding environment variable is overridden.

WARNING: If any long command-line options are used, the long form of all other command-line options must be used. Mixing long and short options is not supported.

Optimization

The configure.sh script will accept an optimization level to pass to the compiler. Because bc is orders of magnitude faster with optimization, I highly recommend package and distro maintainers pass the highest optimization level available in CC to configure.sh with the -O flag or --opt option, as follows:

./configure.sh -O3
./configure.sh --opt 3

Both commands are equivalent.

The build and install can then be run as normal:

make
make install

As usual, configure.sh will also accept additional CFLAGS on the command line, so for SSE4 architectures, the following can add a bit more speed:

CFLAGS="-march=native -msse4" ./configure.sh -O3
make
make install

Building with link-time optimization (-flto in clang) can further increase the performance. I highly recommend doing so.

I do NOT* recommend building with -march=native; doing so reduces this bc's performance.

Manual stripping is not necessary; non-debug builds are automatically stripped in the link stage.

Debug Builds

Debug builds (which also disable optimization if no optimization level is given and if no extra CFLAGS are given) can be enabled with either the -g flag or the --debug option, as follows:

./configure.sh -g
./configure.sh --debug

Both commands are equivalent.

The build and install can then be run as normal:

make
make install

Stripping Binaries

By default, when bc and dc are not built in debug mode, the binaries are stripped. Stripping can be disabled with either the -T or the --disable-strip option, as follows:

./configure.sh -T
./configure.sh --disable-strip

Both commands are equivalent.

The build and install can then be run as normal:

make
make install

Binary Size

When built with both calculators, all available features, and -Os using clang and musl, the executable is 140.4 kb (140,386 bytes) on x86_64. That isn't much for what is contained in the binary, but if necessary, it can be reduced.

The single largest user of space is the bc calculator. If just dc is needed, the size can be reduced to 107.6 kb (107,584 bytes).

The next largest user of space is history support. If that is not needed, size can be reduced (for a build with both calculators) to 119.9 kb (119,866 bytes).

There are several reasons that history is a bigger user of space than dc itself:

  • dc's lexer and parser are tiny compared to bc's because dc code is almost already in the form that it is executed in, while bc has to not only adjust the form to be executable, it has to parse functions, loops, if statements, and other extra features.
  • dc does not have much extra code in the interpreter.
  • History has a lot of const data for supporting UTF-8 terminals.
  • History pulls in a bunch of more code from the libc.

The next biggest user is extra math support. Without it, the size is reduced to 124.0 kb (123,986 bytes) with history and 107.6 kb (107,560 bytes) without history.

The reasons why extra math support is bigger than dc, besides the fact that dc is small already, are:

  • Extra math supports adds an extra math library that takes several kilobytes of constant data space.
  • Extra math support includes support for a pseudo-random number generator, including the code to convert a series of pseudo-random numbers into a number of arbitrary size.
  • Extra math support adds several operators.

The next biggest user is dc, so if just bc is needed, the size can be reduced to 128.1 kb (128,096 bytes) with history and extra math support, 107.6 kb (107,576 bytes) without history and with extra math support, and 95.3 kb (95,272 bytes) without history and without extra math support.

Note: all of these binary sizes were compiled using musl 1.2.0 as the libc, making a fully static executable, with clang 9.0.1 (well, musl-clang using clang 9.0.1) as the compiler and using -Os optimizations. These builds were done on an x86_64 machine running Gentoo Linux.

Testing

The default test suite can be run with the following command:

make test

To test bc only, run the following command:

make test_bc

To test dc only, run the following command:

make test_dc

This bc, if built, assumes a working, GNU-compatible bc, installed on the system and in the PATH, to generate some tests, unless the -G flag or --disable-generated-tests option is given to configure.sh, as follows:

./configure.sh -G
./configure.sh --disable-generated-tests

After running configure.sh, build and run tests as follows:

make
make test

This dc also assumes a working, GNU-compatible dc, installed on the system and in the PATH, to generate some tests, unless one of the above options is given to configure.sh.

To generate test coverage, pass the -c flag or the --coverage option to configure.sh as follows:

./configure.sh -c
./configure.sh --coverage

Both commands are equivalent.

WARNING: Both bc and dc must be built for test coverage. Otherwise, configure.sh will give an error.