Copyright © 2009 John Maddock
The bcp utility is a tool for extracting subsets of Boost, it's useful for
Boost authors who want to distribute their library separately from Boost, and
for Boost users who want to distribute a subset of Boost with their application.
bcp can also report on which parts of Boost your code is dependent on, and
what licences are used by those dependencies.
bcp scoped_ptr /foo
Copies boost/scoped_ptr.hpp and dependencies to /foo.
bcp boost/regex.hpp /foo
Copies boost/regex.hpp and all dependencies including the regex source code
(in libs/regex/src) and build files (in libs/regex/build) to /foo. Does not
copy the regex documentation, test, or example code. Also does not copy the
Boost.Build system.
bcp regex /foo
Copies the full regex lib (in libs/regex) including dependencies (such as the
boost.test source required by the regex test programs) to /foo. Does not copy
the Boost.Build system.
bcp --namespace=myboost --namespace-alias regex config build /foo
Copies the full regex lib (in libs/regex) plus the config lib (libs/config)
and the build system (tools/build) to /foo including all the dependencies.
Also renames the boost namespace to myboost and changes
the filenames of binary libraries to begin with the prefix "myboost"
rather than "boost". The --namespace-alias option makes namespace boost
an alias of the new name.
bcp --scan --boost=/boost foo.cpp bar.cpp boost
Scans the [non-boost] files foo.cpp and bar.cpp for boost dependencies and
copies those dependencies to the sub-directory boost.
bcp --report regex.hpp boost-regex-report.html
Creates a HTML report called boost-regex-report.html for the boost module regex.hpp.
The report contains license information, author details, and file dependencies.
bcp --list [options] module-list
Outputs a list of all the files in module-list including dependencies.
bcp [options] module-list output-path
Copies all the files found in module-list to output-path
bcp --report [options] module-list html-file
Outputs a html report file containing:
-
All the licenses in effect, plus the files using each license, and the
copyright holders using each license.
-
Any files with no recognizable license (please report these to the boost
mailing lists).
-
Any files with no recognizable copyright holders (please report these
to the boost mailing lists).
-
All the copyright holders and the files on which they hold copyright.
-
File dependency information - indicates the reason for the inclusion
of any particular file in the dependencies found.
--boost=path
Sets the location of the boost tree to path. If this option is not provided
then the current path is assumed to be the root directory of the Boost tree.
--namespace=newname
When copying files, all occurances of the boost namespace will get renamed
to "newname". Also renames Boost binaries to use "newname"
rather than "boost" as a prefix.
Often used in conjunction with the --namespace-alias option, this allows
two different Boost versions to be used in the same program, but not in the
same translation unit.
--namespace-alias
When used in conjunction with the --namespace option, then namespace boost
will be declared as an alias of the new namespace name. This allows existing
code that relies on Boost code being in namespace
boost to compile unchanged, while
retaining the "strong versioning" that can be achieved with a namespace
change.
--scan
Treats the module list as a list of (probably non-boost) files to scan for
boost dependencies, the files listed in the module list are not copied (or
listed), only the boost files upon which they depend.
--svn
Only copy files under svn version control.
--unix-lines
Make sure that all copied files use Unix style line endings.
When the --scan option is not used then a list of boost files or library
names to copy, this can be:
-
The name of a tool: for example "build" will find "tools/build".
-
The name of a library: for example "regex".
-
The title of a header: for example "scoped_ptr" will find "boost/scoped_ptr.hpp".
-
The name of a header: for example "scoped_ptr.hpp" will find
"boost/scoped_ptr.hpp".
-
The name of a file: for example "boost/regex.hpp".
When the --scan option is used, then a list of (probably non-boost) files
to scan for boost dependencies, the files in the module list are not therefore
copied/listed.
The path to which files will be copied (this path must exist).
File dependencies are found as follows:
-
C++ source files are scanned for #includes, all #includes present in
the boost source tree will then be scanned for their dependencies and
so on.
-
C++ source files are associated with the name of a library, if that library
has source code (and possibly build data), then include that source in
the dependencies.
-
C++ source files are checked for dependencies on Boost.test (for example
to see if they use cpp_main as an entry point).
-
HTML files are scanned for immediate dependencies (images and style sheets,
but not links).
It should be noted that in practice bcp can produce a rather "fat"
list of dependencies, reasons for this include:
-
It searches for library names first, so using "regex" as a
name will give you everything in the libs/regex directory and everything
that depends on. This can be a long list as all the regex test and example
programs will get scanned for their dependencies. If you want a more
minimal list, then try using the names of the headers you are actually
including, or use the --scan option to scan your source code.
-
If you include the header of a library with separate source, then you
get that libraries source and all it's dependencies. This is deliberate
and in general those extra dependencies are needed.
-
When you include a header, bcp doesn't know what compiler you're using,
so it follows all possible preprocessor paths. If you're distributing
a subset of Boost with you're application then that is what you want
to have happen in general.
The last point above can result in a substantial increase in the number of
headers found compared to most peoples expectations. For example bcp finds
274 header dependencies for boost/shared_ptr.hpp: by running bcp in report
mode we can see why all these headers have been found as dependencies:
-
All of the Config library headers get included (52 headers, would be
about 6 for one compiler only).
-
A lot of MPL and type traits code that includes workarounds for broken
compilers that you may or may not need. Tracing back through the code
shows that most of these aren't needed unless the user has defined BOOST_SP_USE_QUICK_ALLOCATOR,
however bcp isn't aware of whether that preprocessor path will be taken
or not, so the headers get included just in case. This adds about 48
headers (type traits), plus another 49 from MPL.
-
The Preprocessor library gets used heavily by MPL: this adds another
96 headers.
-
The Shared Pointer library contains a lot of platform specific code,
split up into around 22 headers: normally your compiler would need only
a couple of these files.
As you can see the number of dependencies found are much larger than those
used by any single compiler, however if you want to distribute a subset of
Boost that's usable in any configuration, by any compiler, on any platform
then that's exactly what you need. If you want to figure out which Boost
headers are being used by your specific compiler then the best way to find
out is to prepocess the code and scan the output for boost header includes.
You should be aware that the result will be very platform and compiler specific,
and may not contain all the headers needed if you so much as change a compiler
switch (for example turn on threading support).
