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 the following command:
./configure.sh -h
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.
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. 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.
This bc supports CC, HOSTCC, HOST_CC, CFLAGS, HOSTCFLAGS, HOST_CFLAGS, CPPFLAGS, LDFLAGS, LDLIBS, PREFIX, DESTDIR, BINDIR, DATAROOTDIR, DATADIR, MANDIR, MAN1DIR, LOCALEDIR EXECSUFFIX 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.
CCC compiler for the target system. CC must be compatible with POSIX c99 behavior and options.
Defaults to c99.
HOSTCC or HOST_CCC compiler for the host system, used only in cross compiling.
Defaults to $CC.
CFLAGSCommand-line flags that will be passed verbatim to CC.
Defaults to empty.
HOSTCFLAGS or HOST_CFLAGSCommand-line flags that will be passed verbatim to HOSTCC or HOST_CC.
Defaults to $CFLAGS.
CPPFLAGSCommand-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.
LDFLAGSCommand-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.
LDLIBSLibraries 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.
PREFIXThe prefix to install to.
Defaults to /usr/local.
DESTDIRPath to prepend onto PREFIX. This is mostly for distro and package maintainers.
Defaults to empty.
BINDIRThe directory to install binaries in.
Defaults to $PREFIX/bin.
DATAROOTDIRThe root directory to install data files in.
Defaults to $PREFIX/share.
DATADIRThe directory to install data files in.
Defaults to $DATAROOTDIR.
MANDIRThe directory to install manpages in.
Defaults to $DATADIR/man
MAN1DIRThe directory to install Section 1 manpages in. Because both bc and dc are Section 1 commands, this is the only relevant section directory.
Defaults to $MANDIR/man1.
LOCALEDIRThe directory to install locales in.
Defaults to $DATAROOTDIR/locale.
EXECSUFFIXThe 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.
GEN_EMUThe 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.
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. Also, array references are turned off automatically when building only dc.
bc OnlyTo build bc only (no dc), use either one of the following commands for the configure step:
./configure.sh -b ./configure.sh -D
Those two commands are equivalent.
Warning: It is an error to use those options if bc has also been disabled (see below).
dc OnlyTo build dc only (no bc), use either one of the following commands for the configure step:
./configure.sh -d ./configure.sh -B
Those two commands are equivalent.
Warning: It is an error to use those options if dc has also been disabled (see above).
To disable signal handling, use the -S flag in the configure step:
./configure.sh -S
To disable signal handling, use the -H flag in the configure step:
./configure.sh -H
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.
To disable locale support (use only English), use the -N flag in the configure step:
./configure.sh -N
Array references are an extension to the standard first implemented by the GNU bc. They can be disabled by using the -R flag in the configure step:
./configure.sh -R
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.
Extra operators can be disabled using the -E flag in the configure step:
./configure.sh -E
This bc also has a larger library that is only enabled if extra operators are. More information about the functions can be found in the Extended Library section of the full manual.
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, as follows:
./configure.sh -O3 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.
Manual stripping is not necessary; non-debug builds are automatically stripped in the link stage.
Debug builds (which also disable optimization if no optimization level is given and if no extra CFLAGS are given) can be enabled with:
./configure.sh -g make make install
When built with both calculators, all available features, and -Os using clang, the executable is 101 kb (100,912 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 to 72 kb (72,223 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 84 kb (84,448 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.dc does not have much extra code for runtime.The next biggest user is dc, so if just bc is needed, the size can be reduced to 89 kb (88,624 bytes) with history and 76 kb (76,256 bytes) without history.
The next biggest user is signal handling. Without it, the size (with both calculators) is reduced to 97 kb (97,800 bytes) with history and 84 kb (84,416 bytes) without history.
The next largest user is extra math support. If this is not needed, the size (with both calculators) can be reduced to 97 kb (96,808 bytes) with history and signal handling, 80 kb (80,344 bytes) without history, 93 kb (92,696 bytes) without signal handling, and 76 kb (76,216 bytes) without both.
While disabling references reduces the amount of code, because of alignment and other reasons, it only reduces the executable size if extra math is disabled (to 93 kb or 92,712 bytes).
The default test suite can be run with the following command:
make test
All available tests can be run by running the following command:
make test_all
This bc, if built, assumes a working, GNU-compatible bc in the PATH to generate some tests, unless the -G option is given to configure.sh, as follows:
./configure.sh -G make make test
This dc also assumes a working, GNU-compatible dc in the PATH to generate some tests, unless the above option is given to configure.sh.