$szTitle = "Reference"; include "../../../_header.inc"; ?>
Home | Libraries | People | FAQ | More |
bjam's first job upon startup is to load the Jam code that
implements the build system. To do this, it searches for a file
called boost-build.jam
, first in the invocation directory, then
in its parent and so forth up to the filesystem root, and finally
in the directories specified by the environment variable
BOOST_BUILD_PATH. When found, the file is interpreted, and should
specify the build system location by calling the boost-build
rule:
rule boost-build ( location ? )
If location is a relative path, it is treated as relative to
the directory of boost-build.jam
. The directory specified by
that location and the directories in BOOST_BUILD_PATH are then searched for
a file called bootstrap.jam
, which is expected to
bootstrap the build system. This arrangement allows the build
system to work without any command-line or environment variable
settings. For example, if the build system files were located in a
directory "build-system/" at your project root, you might place a
boost-build.jam
at the project root containing:
boost-build build-system ;
In this case, running bjam anywhere in the project tree will automatically find the build system.
The default bootstrap.jam
, after loading some standard
definitions, loads two site-config.jam
and user-config.jam
.
This section contains the list of all rules that can be used in Jamfile—both rules that define new targets and auxiliary rules.
exe
Creates an executable file. See the section called “Programs”.
lib
Creates an library file. See the section called “Libraries”.
install
Installs built targets and other files. See the section called “Installing”.
alias
Creates an alias for other targets. See the section called “Alias”.
unit-test
Creates an executable that will be automatically run. See the section called “Testing”.
compile
, compile-fail
, link
, link-fail
, run
, run-fail
Specialized rules for testing. See the section called “Testing”.
obj
Creates an object file. Useful when a single source file must be compiled with special properties.
glob
The glob
rule takes a list shell pattern
and returns the list of files in the project's source directory that
match the pattern. For example:
lib tools : [ glob *.cpp ] ;
It is possible to also pass a second argument—the list of exclude patterns. The result will then include the list of files patching any of include patterns, and not matching any of the exclude patterns. For example:
lib tools : [ glob *.cpp : file_to_exclude.cpp bad*.cpp ] ;
glob-tree
The glob-tree
is similar to the
glob
except that it operates recursively from
the directory of the containing Jamfile. For example:
ECHO [ glob-tree *.cpp : .svn ] ;
will print the names of all C++ files in your project. The
.svn
exclude pattern prevents the
glob-tree
rule from entering administrative
directories of the Subversion version control system.
project
Declares project id and attributes, including project requirements. See the section called “Projects”.
use-project
Assigns a symbolic project ID to a project at a given path. This rule must be better documented!
explicit
The explicit
rule takes a single
parameter—a list of target names. The named targets will
be marked explicit, and will be built only if they are explicitly
requested on the command line, or if their dependents are built.
Compare this to ordinary targets, that are built implicitly when
their containing project is built.
constant
Sets project-wide constant. Takes two parameters: variable name and a value and makes the specified variable name accessible in this Jamfile and any child Jamfiles. For example:
constant VERSION : 1.34.0 ;
path-constant
Same as constant
except that
the value is treated as path relative to Jamfile location. For example,
if bjam is invoked in the current directory,
and Jamfile in helper
subdirectory has:
path-constant DATA : data/a.txt ;
then the variable DATA
will be set to
helper/data/a.txt
, and if bjam
is invoked from the helper
directory, then
the variable DATA
will be set to
data/a.txt
.
build-project
Cause some other project to be built. This rule takes a single parameter—a directory name relative to the containing Jamfile. When the containing Jamfile is built, the project located at that directory will be built as well. At the moment, the parameter to this rule should be a directory name. Project ID or general target references are not allowed.
test-suite
This rule is deprecated and equivalent to
alias
.
variant
A feature combining several low-level features, making it easy to request common build configurations.
Allowed values:
debug
, release
,
profile
.
The value debug
expands to
<optimization>off <debug-symbols>on <inlining>off <runtime-debugging>on
The value release
expands to
<optimization>speed <debug-symbols>off <inlining>full <runtime-debugging>off
The value profile
expands to the same as
release
, plus:
<profiling>on <debug-symbols>on
Users can define their own build variants using the
variant
rule from the common
module.
Note: Runtime debugging is on in debug builds to suit the expectations of people used to various IDEs.
link
Allowed values: shared
,
static
A feature controling how libraries are built.
runtime-link
Allowed values: shared
,
static
Controls if a static or shared C/C++ runtime should be used. There are some restrictions how this feature can be used, for example on some compilers an application using static runtime should not use shared libraries at all, and on some compilers, mixing static and shared runtime requires extreme care. Check your compiler documentation for more details.
source
<source>X
feature has the same effect on
building a target as putting X in the list of sources. It is useful
when you want to add the same source to all targets in the project
(you can put <source> in requirements) or to conditionally
include a source (using conditional requirements, see the section called “Conditions and alternatives”). See also the <library>
feature.
library
<source>
feature, except that it takes effect only for linking. When you want
to link all targets in a Jamfile to certain library, the
<library>
feature is preferred over
<source>X
-- the latter will add the library to
all targets, even those that have nothing to do with libraries.
dependency
use
#include
paths) of some library
to be applied, but do not want to link to it.
dll-path
dll-path
and hardcode-dll-paths
properties useful?
”
in the section called “Frequently Asked Questions” for details.
hardcode-dll-paths
Controls automatic generation of dll-path properties.
Allowed values:
true
, false
. This property is
specific to Unix systems. If an executable is built with
<hardcode-dll-paths>true
, the generated binary
will contain the list of all the paths to the used shared libraries.
As the result, the executable can be run without changing system
paths to shared libraries or installing the libraries to system
paths. This is very
convenient during development. Plase see the FAQ entry for details. Note that on Mac
OSX, the paths are unconditionally hardcoded by the linker, and it
is not possible to disable that behaviour.
cflags
, cxxflags
, linkflags
cflags
that is both the C and
C++ compilers, for cxxflags
that is the C++ compiler
and for linkflags
that is the linker. The features are
handy when you are trying to do something special that cannot be
achieved by a higher-level feature in Boost.Build.
include
warnings
<warnings>
feature controls the warning level
of compilers. It has the following values:
off
- disables all warnings.
on
- enables default warning level for the tool.
all
- enables all warnings.
all
.
warnings-as-errors
<warnings-as-errors>
makes it possible to
treat warnings as errors and abort compilation on a warning. The
value on
enables this behaviour. The default value is
off
.
build
Allowed values: no
The build
feature is used to conditionally disable
build of a target. If <build>no
is in properties
when building a target, build of that target is skipped. Combined
with conditional requirements this allows you to skip building some
target in configurations where the build is known to fail.
tag
The tag
feature is used to customize
the name of the generated files. The value should have the form:
@rulename
where
rulename
should be a name of a rule with the
following signature:
rule tag ( name : type ? : property-set )
The rule will be called for each target with the default name computed by Boost.Build, the type of the target, and property set. The rule can either return a string that must be used as the name of the target, or an empty string, in which case the default name will be used.
Most typical use of the tag
feature is to
encode build properties, or library version in library target names. You
should take care to return non-empty string from the tag rule only for
types you care about — otherwise, you might end up modifying
names of object files, generated header file and other targets for which
changing names does not make sense.
debug-symbols
Allowed values: on
, off
.
The debug-symbols
feature specifies if
produced object files, executables and libraries should include
debug information.
Typically, the value of this feature is implicitly set by the
variant
feature, but it can be explicitly
specified by the user. The most common usage is to build
release variant with debugging information.
architecture
The architecture
features specifies
the general processor familty to generate code for.
instruction-set
Allowed values: depend on the used toolset.
The instruction-set
specifies for which
specific instruction set the code should be generated. The
code in general might not run on processors with older/different
instruction sets.
While Boost.Build allows a large set of possible values for this features, whether a given value works depends on which compiler you use. Please see the section called “C++ Compilers” for details.
address-model
Allowed values: 32
, 64
.
The address-model
specifies if 32-bit or
64-bit code should be generated by the compiler. Whether this feature
works depends on the used compiler, its version, how the compiler is
configured, and the values of the architecture
instruction-set
features. Please see the section called “C++ Compilers”
for details.
c++-template-depth
Allowed values: Any positive integer.
This feature allows configuring a C++ compiler with the maximal template instantiation depth parameter. Specific toolsets may or may not provide support for this feature depending on whether their compilers provide a corresponding command-line option.
Note: Due to some internal details in the current Boost Build implementation it is not possible to have features whose valid values are all positive integer. As a workaround a large set of allowed values has been defined for this feature and, if a different one is needed, user can easily add it by calling the feature.extend rule.
Boost.Build comes with support for a large number of C++ compilers, and other tools. This section documents how to use those tools.
Before using any tool, you must declare your intention, and possibly
specify additional information about the tool's configuration. This is
done by calling the using
rule, typically in your
user-config.jam
, for example:
using gcc ;
additional parameters can be passed just like for other rules, for example:
using gcc : 4.0 : g++-4.0 ;
The options that can be passed to each tool are documented in the subsequent sections.
This section lists all Boost.Build modules that support C++
compilers and documents how each one can be initialized. The name
of support module for compiler is also the value for
the toolset
feature that can be used to explicitly
request that compiler.
The gcc
module supports the
GNU C++ compiler
on Linux, a number of Unix-like system including MacOS X, SunOS and
BeOS, and on Windows (either Cygwin
or MinGW).
The gcc
module is initialized using the following
syntax:
using gcc : [version
] : [c++-compile-command
] : [compiler options
] ;
This statement may be repeated several times, if you want to configure several versions of the compiler.
If the version is not explicitly specified, it will be
automatically detected by running the compiler with the -v
option. If the command is not specified, the g++
binary will be searched in PATH
.
The following options can be provided, using <
syntax:option-name
>option-value
cflags
Specifies additional compiler flags that will be used when compiling C sources.
cxxflags
Specifies additional compiler flags that will be used when compiling C++ sources.
compileflags
Specifies additional compiler flags that will be used when compiling both C and C++ sources.
linkflags
Specifies additional command line options that will be passed to the linker.
root
Specifies root directory of the compiler installation. This option is necessary only if it is not possible to detect this information from the compiler command—for example if the specified compiler command is a user script.
rc
Specifies the resource compiler command that will be used with the version of gcc that is being configured. This setting makes sense only for Windows and only if you plan to use resource files. By default windres will be used.
rc-type
Specifies the type of resource compiler. The value can
be either windres
for msvc resource compiler,
or rc
for borland's resource compiler.
address-model=64
, and the instruction-set
feature should refer to a 64 bit processor. Currently, those
include nocona
, opteron
,
athlon64
and athlon-fx
.
The msvc
module supports the
Microsoft Visual
C++ command-line tools on Microsoft Windows. The supported
products and versions of command line tools are listed below:
Visual Studio 2008—9.0
Visual Studio 2005—8.0
Visual Studio .NET 2003—7.1
Visual Studio .NET—7.0
Visual Studio 6.0, Service Pack 5—6.5
The msvc
module is initialized using the following
syntax:
using msvc : [version
] : [c++-compile-command
] : [compiler options
] ;
This statement may be repeated several times, if you want to configure several versions of the compiler.
If the version is not explicitly specified, the most recent
version found in the registry will be used instead. If the special
value all
is passed as the version, all versions found in
the registry will be configured. If a version is specified, but the
command is not, the compiler binary will be searched in standard
installation paths for that version, followed by PATH
.
The compiler command should be specified using forward slashes, and quoted.
The following options can be provided, using <
syntax:option-name
>option-value
cflags
Specifies additional compiler flags that will be used when compiling C sources.
cxxflags
Specifies additional compiler flags that will be used when compiling C++ sources.
compileflags
Specifies additional compiler flags that will be used when compiling both C and C++ sources.
linkflags
Specifies additional command line options that will be passed to the linker.
assembler
The command that compiles assembler sources. If
not specified, ml will be used. The command
will be invoked after the setup script was executed and adjusted
the PATH
variable.
compiler
The command that compiles C and C++ sources. If
not specified, cl will be used. The command
will be invoked after the setup script was executed and adjusted
the PATH
variable.
compiler-filter
Command through which to pipe the output of running the compiler. For example to pass the output to STLfilt.
idl-compiler
The command that compiles Microsoft COM interface
definition files. If not specified, midl will
be used. The command will be invoked after the setup script was
executed and adjusted the PATH
variable.
linker
The command that links executables and dynamic
libraries. If not specified, link will be used.
The command will be invoked after the setup script was executed
and adjusted the PATH
variable.
mc-compiler
The command that compiles Microsoft message
catalog files. If not specified, mc will be
used. The command will be invoked after the setup script was
executed and adjusted the PATH
variable.
resource-compiler
The command that compiles resource files. If not
specified, rc will be used. The command will be
invoked after the setup script was executed and adjusted the
PATH
variable.
setup
The filename of the global environment setup script to run before invoking any of the tools defined in this toolset. Will not be used in case a target platform specific script has been explicitly specified for the current target platform. Used setup script will be passed the target platform identifier (x86, x86_amd64, x86_ia64, amd64 or ia64) as a arameter. If not specified a default script is chosen based on the used compiler binary, e.g. vcvars32.bat or vsvars32.bat.
setup-amd64
, setup-i386
, setup-ia64
The filename of the target platform specific environment setup script to run before invoking any of the tools defined in this toolset. If not specified the global environment setup script is used.
Starting with version 8.0, Microsoft Visual Studio can generate binaries for 64-bit processor, both 64-bit flavours of x86 (codenamed AMD64/EM64T), and Itanium (codenamed IA64). In addition, compilers that are itself run in 64-bit mode, for better performance, are provided. The complete list of compiler configurations are as follows (we abbreviate AMD64/EM64T to just AMD64):
32-bit x86 host, 32-bit x86 target
32-bit x86 host, 64-bit AMD64 target
32-bit x86 host, 64-bit IA64 target
64-bit AMD64 host, 64-bit AMD64 target
64-bit IA64 host, 64-bit IA64 target
The 32-bit host compilers can be always used, even on 64-bit Windows. On the contrary, 64-bit host compilers require both 64-bit host processor and 64-bit Windows, but can be faster. By default, only 32-bit host, 32-bit target compiler is installed, and additional compilers need to be installed explicitly.
To use 64-bit compilation you should:
Configure you compiler as usual. If you provide a path to the compiler explicitly, provide the path to the 32-bit compiler. If you try to specify the path to any of 64-bit compilers, configuration will not work.
When compiling, use address-model=64
,
to generate AMD64 code.
To generate IA64 code, use
architecture=ia64
The (AMD64 host, AMD64 target) compiler will be used automatically when you are generating AMD64 code and are running 64-bit Windows on AMD64. The (IA64 host, IA64 target) compiler will never be used, since nobody has an IA64 machine to test.
It is believed that AMD64 and EM64T targets are essentially
compatible. The compiler options /favor:AMD64
and
/favor:EM64T
, which are accepted only by AMD64
targeting compilers, cause the generated code to be tuned to a
specific flavor of 64-bit x86. Boost.Build will make use of those
options depending on the value of theinstruction-set
feature.
The intel-linux
and intel-win
modules
support the Intel C++ command-line compiler—the Linux
and
Windows versions respectively.
The module is initialized using the following syntax:
using intel-linux : [version
] : [c++-compile-command
] : [compiler options
] ;
or
using intel-win : [version
] : [c++-compile-command
] : [compiler options
] ;
respectively.
This statement may be repeated several times, if you want to configure several versions of the compiler.
If compiler command is not specified, then Boost.Build will
look in PATH
for an executable icpc
(on Linux), or icc.exe (on Windows).
The following options can be provided, using <
syntax:option-name
>option-value
cflags
Specifies additional compiler flags that will be used when compiling C sources.
cxxflags
Specifies additional compiler flags that will be used when compiling C++ sources.
compileflags
Specifies additional compiler flags that will be used when compiling both C and C++ sources.
linkflags
Specifies additional command line options that will be passed to the linker.
The Linux version supports the following additional options:
root
Specifies root directory of the compiler installation. This option is necessary only if it is not possible to detect this information from the compiler command—for example if the specified compiler command is a user script.
The acc
module supports the
HP aC++ compiler
for the HP-UX operating system.
The module is initialized using the following syntax:
using acc : [version
] : [c++-compile-command
] : [compiler options
] ;
This statement may be repeated several times, if you want to configure several versions of the compiler.
If the command is not specified, the aCC
binary will be searched in PATH
.
The following options can be provided, using <
syntax:option-name
>option-value
cflags
Specifies additional compiler flags that will be used when compiling C sources.
cxxflags
Specifies additional compiler flags that will be used when compiling C++ sources.
compileflags
Specifies additional compiler flags that will be used when compiling both C and C++ sources.
linkflags
Specifies additional command line options that will be passed to the linker.
The borland
module supports the command line
C++ compiler included in
C++ Builder 2006
product and earlier version of it, running on Microsoft Windows.
The supported products are listed below. The version reported by the command lines tools is also listed for reference.:
C++ Builder 2006—5.8.2
CBuilderX—5.6.5, 5.6.4 (depending on release)
CBuilder6—5.6.4
Free command line tools—5.5.1
The module is initialized using the following syntax:
using borland : [version
] : [c++-compile-command
] : [compiler options
] ;
This statement may be repeated several times, if you want to configure several versions of the compiler.
If the command is not specified, Boost.Build will search for
a binary named bcc32 in PATH
.
The following options can be provided, using <
syntax:option-name
>option-value
cflags
Specifies additional compiler flags that will be used when compiling C sources.
cxxflags
Specifies additional compiler flags that will be used when compiling C++ sources.
compileflags
Specifies additional compiler flags that will be used when compiling both C and C++ sources.
linkflags
Specifies additional command line options that will be passed to the linker.
The como-linux
and the como-win
modules supports the
Comeau C/C++ Compiler
on Linux and Windows respectively.
The module is initialized using the following syntax:
using como-linux : [version
] : [c++-compile-command
] : [compiler options
] ;
This statement may be repeated several times, if you want to configure several versions of the compiler.
If the command is not specified, Boost.Build will search for
a binary named como in
PATH
.
The following options can be provided, using <
syntax:option-name
>option-value
cflags
Specifies additional compiler flags that will be used when compiling C sources.
cxxflags
Specifies additional compiler flags that will be used when compiling C++ sources.
compileflags
Specifies additional compiler flags that will be used when compiling both C and C++ sources.
linkflags
Specifies additional command line options that will be passed to the linker.
Before using the Windows version of the compiler, you need to
setup necessary environment variables per compiler's documentation. In
particular, the COMO_XXX_INCLUDE
variable should be
set, where XXX
corresponds to the used backend C
compiler.
The cw
module support CodeWarrior compiler,
originally produced by Metrowerks and presently developed by
Freescale. Boost.Build supports only the versions of the compiler that
target x86 processors. All such versions were released by Metrowerks
before aquisition and are not sold any longer. The last version known
to work is 9.4.
The module is initialized using the following syntax:
using cw : [version
] : [c++-compile-command
] : [compiler options
] ;
This statement may be repeated several times, if you want to configure several versions of the compiler.
If the command is not specified, Boost.Build will search for a
binary named mwcc in default installation paths and
in PATH
.
The following options can be provided, using <
syntax:option-name
>option-value
cflags
Specifies additional compiler flags that will be used when compiling C sources.
cxxflags
Specifies additional compiler flags that will be used when compiling C++ sources.
compileflags
Specifies additional compiler flags that will be used when compiling both C and C++ sources.
linkflags
Specifies additional command line options that will be passed to the linker.
root
Specifies root directory of the compiler installation. This option is necessary only if it is not possible to detect this information from the compiler command—for example if the specified compiler command is a user script.
setup
The command that sets up environment variables prior to invoking the compiler. If not specified, cwenv.bat alongside the compiler binary will be used.
compiler
The command that compiles C and C++ sources.
If not specified, mwcc will be used. The
command will be invoked after the setup script was
executed and adjusted the PATH
variable.
linker
The command that links executables and dynamic
libraries.
If not specified, mwld will be used. The
command will be invoked after the setup script was
executed and adjusted the PATH
variable.
The dmc
module supports the
Digital Mars C++ compiler.
The module is initialized using the following syntax:
using dmc : [version
] : [c++-compile-command
] : [compiler options
] ;
This statement may be repeated several times, if you want to configure several versions of the compiler.
If the command is not specified, Boost.Build will search for
a binary named dmc in
PATH
.
The following options can be provided, using <
syntax:option-name
>option-value
cflags
Specifies additional compiler flags that will be used when compiling C sources.
cxxflags
Specifies additional compiler flags that will be used when compiling C++ sources.
compileflags
Specifies additional compiler flags that will be used when compiling both C and C++ sources.
linkflags
Specifies additional command line options that will be passed to the linker.
The hp_cxx
modules supports the
HP C++ Compiler for Tru64 Unix.
The module is initialized using the following syntax:
using hp_cxx : [version
] : [c++-compile-command
] : [compiler options
] ;
This statement may be repeated several times, if you want to configure several versions of the compiler.
If the command is not specified, Boost.Build will search for
a binary named hp_cxx in PATH
.
The following options can be provided, using <
syntax:option-name
>option-value
cflags
Specifies additional compiler flags that will be used when compiling C sources.
cxxflags
Specifies additional compiler flags that will be used when compiling C++ sources.
compileflags
Specifies additional compiler flags that will be used when compiling both C and C++ sources.
linkflags
Specifies additional command line options that will be passed to the linker.
The sun
module supports the
Sun Studio C++ compilers for the Solaris OS.
The module is initialized using the following syntax:
using sun : [version
] : [c++-compile-command
] : [compiler options
] ;
This statement may be repeated several times, if you want to configure several versions of the compiler.
If the command is not specified, Boost.Build will search for
a binary named CC
in /opt/SUNWspro/bin
and in
PATH
.
When using this compiler on complex C++ code, such as the
Boost C++ library, it is
recommended to specify the following options when intializing the
sun
module:
-library=stlport4 -features=tmplife -features=tmplrefstatic
See the Sun C++ Frontend Tales for details.
The following options can be provided, using <
syntax:option-name
>option-value
cflags
Specifies additional compiler flags that will be used when compiling C sources.
cxxflags
Specifies additional compiler flags that will be used when compiling C++ sources.
compileflags
Specifies additional compiler flags that will be used when compiling both C and C++ sources.
linkflags
Specifies additional command line options that will be passed to the linker.
address-model=64
property.
The vacpp
module supports the
IBM Visual
Age C++ Compiler, for the AIX operating system. Versions
7.1 and 8.0 are known to work.
The module is initialized using the following syntax:
using vacpp ;
The module does not accept any initialization options. The
compiler should be installed in the /usr/vacpp/bin
directory.
Later versions of Visual Age are known as XL C/C++. They
were not tested with the the vacpp
module.
Boost.Build provides special support for some third-party C++ libraries, documented below.
The STLport library is an alternative implementation of C++ runtime library. Boost.Build supports using that library on Windows platfrom. Linux is hampered by different naming of libraries in each STLport version and is not officially supported.
Before using STLport, you need to configure it in
user-config.jam
using the following syntax:
using stlport : [version
] :header-path
: [library-path
] ;
Where version
is the version of
STLport, for example 5.1.4
,
headers
is the location where
STLport headers can be found, and libraries
is the location where STLport libraries can be found.
The version should always be provided, and the library path should
be provided if you're using STLport's implementation of
iostreams. Note that STLport 5.* always uses its own iostream
implementation, so the library path is required.
When STLport is configured, you can build with STLport by
requesting stdlib=stlport
on the command line.
The general overview of the build process was given in the user documentation. This section provides additional details, and some specific rules.
To recap, building a target with specific properties includes the following steps:
applying default build,
selecting the main target alternative to use,
determining "common" properties,
building targets referred by the sources list and dependency properties,
adding the usage requirements produces when building dependencies to the "common" properties,
building the target using generators,
computing the usage requirements to be returned.
When there are several alternatives, one of them must be selected. The process is as follows:
The "common" properties is a somewhat artificial term. Those are the intermediate property set from which both the build request for dependencies and properties for building the target are derived.
Since default build and alternatives are already handled, we have only two inputs: build requests and requirements. Here are the rules about common properties.
Non-free feature can have only one value
A non-conditional property in requirement in always present in common properties.
A property in build request is present in common properties, unless (2) tells otherwise.
If either build request, or requirements (non-conditional or conditional) include an expandable property (either composite, or property with specified subfeature value), the behaviour is equivalent to explicitly adding all expanded properties to build request or requirements.
If requirements include a conditional property, and condiiton of this property is true in context of common properties, then the conditional property should be in common properties as well.
If no value for a feature is given by other rules here, it has default value in common properties.
Those rules are declarative, they don't specify how to compute the common properties. However, they provide enough information for the user. The important point is the handling of conditional requirements. The condition can be satisfied either by property in build request, by non-conditional requirements, or even by another conditional property. For example, the following example works as expected:
exe a : a.cpp : <toolset>gcc:<variant>release <variant>release:<define>FOO ;
A feature is a normalized (toolset-independent)
aspect of a build configuration, such as whether inlining is
enabled. Feature names may not contain the '>
'
character.
Each feature in a build configuration has one or more
associated values. Feature values for non-free features
may not contain the '<
', ':
', or
'=
' characters. Feature values for free features may not
contain the '<
' character.
A property is a (feature,value) pair, expressed as <feature>value.
A subfeature is a feature that only exists in the presence of its parent feature, and whose identity can be derived (in the context of its parent) from its value. A subfeature's parent can never be another subfeature. Thus, features and their subfeatures form a two-level hierarchy.
A value-string for a feature F is a string of
the form
value-subvalue1-subvalue2
...-subvalueN
, where
value
is a legal value for F and
subvalue1
...subvalueN
are legal values of some
of F's subfeatures. For example, the properties
<toolset>gcc <toolset-version>3.0.1
can be
expressed more conscisely using a value-string, as
<toolset>gcc-3.0.1
.
A property set is a set of properties (i.e. a
collection without duplicates), for instance:
<toolset>gcc <runtime-link>static
.
A property path is a property set whose elements have
been joined into a single string separated by slashes. A property
path representation of the previous example would be
<toolset>gcc/<runtime-link>static
.
A build specification is a property set that fully describes the set of features used to build a target.
For free
features, all values are valid. For all other features,
the valid values are explicitly specified, and the build
system will report an error for the use of an invalid
feature-value. Subproperty validity may be restricted so
that certain values are valid only in the presence of
certain other subproperties. For example, it is possible
to specify that the <gcc-target>mingw
property is only valid in the presence of
<gcc-version>2.95.2
.
Each feature has a collection of zero or more of the following attributes. Feature attributes are low-level descriptions of how the build system should interpret a feature's values when they appear in a build request. We also refer to the attributes of properties, so that an incidental property, for example, is one whose feature has the incidental attribute.
incidental
Incidental features are assumed not to affect build products at all. As a consequence, the build system may use the same file for targets whose build specification differs only in incidental features. A feature that controls a compiler's warning level is one example of a likely incidental feature.
Non-incidental features are assumed to affect build products, so the files for targets whose build specification differs in non-incidental features are placed in different directories as described in "target paths" below. [ where? ]
Features of this kind are
propagated to dependencies. That is, if a main target is built using a
propagated
property, the build systems attempts to use the same property
when building any of its dependencies as part of that main
target. For instance, when an optimized exectuable is
requested, one usually wants it to be linked with optimized
libraries. Thus, the <optimization>
feature is
propagated.
Most features have a finite set of allowed values, and can only take on a single value from that set in a given build specification. Free features, on the other hand, can have several values at a time and each value can be an arbitrary string. For example, it is possible to have several preprocessor symbols defined simultaneously:
<define>NDEBUG=1 <define>HAS_CONFIG_H=1
optional
An optional feature is a feature that is not required to appear in a build specification. Every non-optional non-free feature has a default value that is used when a value for the feature is not otherwise specified, either in a target's requirements or in the user's build request. [A feature's default value is given by the first value listed in the feature's declaration. -- move this elsewhere - dwa]
symmetric
A symmetric feature's default value is not automatically included in build variants. Normally a feature only generates a subvariant directory when its value differs from the value specified by the build variant, leading to an assymmetric subvariant directory structure for certain values of the feature. A symmetric feature, when relevant to the toolset, always generates a corresponding subvariant directory.
path
The value of a path feature specifies a path. The path is treated as relative to the directory of Jamfile where path feature is used and is translated appropriately by the build system when the build is invoked from a different directory
implicit
Values of implicit features alone identify the feature. For example, a user is not required to write "<toolset>gcc", but can simply write "gcc". Implicit feature names also don't appear in variant paths, although the values do. Thus: bin/gcc/... as opposed to bin/toolset-gcc/.... There should typically be only a few such features, to avoid possible name clashes.
composite
Composite features actually correspond to groups of properties. For example, a build variant is a composite feature. When generating targets from a set of build properties, composite features are recursively expanded and added to the build property set, so rules can find them if necessary. Non-composite non-free features override components of composite features in a build property set.
dependency
The value of dependency feature if a target reference. When used for building of a main target, the value of dependency feature is treated as additional dependency.
For example, dependency features allow to state that library A depends on library B. As the result, whenever an application will link to A, it will also link to B. Specifying B as dependency of A is different from adding B to the sources of A.
Features that are neither free nor incidental are called base features.
A build variant, or (simply variant) is a special kind of composite feature that automatically incorporates the default values of features that . Typically you'll want at least two separate variants: one for debugging, and one for your release code. [ Volodya says: "Yea, we'd need to mention that it's a composite feature and describe how they are declared, in pacticular that default values of non-optional features are incorporated into build variant automagically. Also, do we wan't some variant inheritance/extension/templates. I don't remember how it works in V1, so can't document this for V2.". Will clean up soon -DWA ]
When a target with certain properties is requested, and that target requires some set of properties, it is needed to find the set of properties to use for building. This process is called property refinement and is performed by these rules
Sometime it's desirable to apply certain requirements only for a specific combination of other properties. For example, one of compilers that you use issues a pointless warning that you want to suppress by passing a command line option to it. You would not want to pass that option to other compilers. Conditional properties allow you to do just that. Their syntax is:
property ( "," property ) * ":" property
For example, the problem above would be solved by:
exe hello : hello.cpp : <toolset>yfc:<cxxflags>-disable-pointless-warning ;
The syntax also allows several properties in the condition, for example:
exe hello : hello.cpp : <os>NT,<toolset>gcc:<link>static ;
Target identifier is used to denote a target. The syntax is:
target-id -> (project-id | target-name | file-name ) | (project-id | directory-name) "//" target-name project-id -> path target-name -> path file-name -> path directory-name -> path
This grammar allows some elements to be recognized as either
To determine the real meaning a check is made if project-id by the specified name exists, and then if main target of that name exists. For example, valid target ids might be:
a -- target in current project lib/b.cpp -- regular file /boost/thread -- project "/boost/thread" /home/ghost/build/lr_library//parser -- target in specific project
Rationale:Target is separated from project by special separator (not just slash), because:
Target reference is used to specify a source target, and may additionally specify desired properties for that target. It has this syntax:
target-reference -> target-id [ "/" requested-properties ] requested-properties -> property-path
For example,
exe compiler : compiler.cpp libs/cmdline/<optimization>space ;
would cause the version of cmdline
library,
optimized for space, to be linked in even if the
compiler
executable is build with optimization for
speed.
Warning | |
---|---|
The information is this section is likely to be outdated and misleading. |
To construct a main target with given properties from sources, it is required to create a dependency graph for that main target, which will also include actions to be run. The algorithm for creating the dependency graph is described here.
The fundamental concept is generator. If encapsulates the notion of build tool and is capable to converting a set of input targets into a set of output targets, with some properties. Generator matches a build tool as closely as possible: it works only when the tool can work with requested properties (for example, msvc compiler can't work when requested toolset is gcc), and should produce exactly the same targets as the tool (for example, if Borland's linker produces additional files with debug information, generator should also).
Given a set of generators, the fundamental operation is to
construct a target of a given type, with given properties, from a
set of targets. That operation is performed by rule
generators.construct
and the used algorithm is described
below.
Each generator, in addition to target types that it can produce, have attribute that affects its applicability in particular sitiation. Those attributes are:
Generator's required and optional properties may not include either free or incidental properties. (Allowing this would greatly complicate caching targets).
When trying to construct a target, the first step is to select all possible generators for the requested target type, which required properties are a subset of requested properties. Generators that were already selected up the call stack are excluded. In addition, if any composing generators were selected up the call stack, all other composing generators are ignored (TODO: define composing generators). The found generators are assigned a rank, which is the number of optional properties present in requested properties. Finally, generators with highest rank are selected for futher processing.
When generators are selected, each is run to produce a list of created targets. This list might include targets that are not of requested types, because generators create the same targets as some tool, and tool's behaviour is fixed. (Note: should specify that in some cases we actually want extra targets). If generator fails, it returns an empty list. Generator is free to call 'construct' again, to convert sources to the types it can handle. It also can pass modified properties to 'construct'. However, a generator is not allowed to modify any propagated properties, otherwise when actually consuming properties we might discover that the set of propagated properties is different from what was used for building sources.
For all targets that are not of requested types, we try to
convert them to requested type, using a second call to
construct
. This is done in order to support
transformation sequences where single source file expands to
several later. See this
message for details.
After all generators are run, it is necessary to decide which of successfull invocation will be taken as final result. At the moment, this is not done. Instead, it is checked whether all successfull generator invocation returned the same target list. Error is issued otherwise.
Because target location is determined by the build system, it is sometimes necessary to adjust properties, in order to not break actions. For example, if there's an action that generates a header, say "a_parser.h", and a source file "a.cpp" which includes that file, we must make everything work as if a_parser.h is generated in the same directory where it would be generated without any subvariants.
Correct property adjustment can be done only after all targets are created, so the approach taken is:
When dependency graph is constructed, each action can be assigned a rule for property adjustment.
When virtual target is actualized, that rule is run and return the final set of properties. At this stage it can use information of all created virtual targets.
In case of quoted includes, no adjustment can give 100% correct results. If target dirs are not changed by build system, quoted includes are searched in "." and then in include path, while angle includes are searched only in include path. When target dirs are changed, we'd want to make quoted includes to be search in "." then in additional dirs and then in the include path and make angle includes be searched in include path, probably with additional paths added at some position. Unless, include path already has "." as the first element, this is not possible. So, either generated headers should not be included with quotes, or first element of include path should be ".", which essentially erases the difference between quoted and angle includes. Note: the only way to get "." as include path into compiler command line is via verbatim compiler option. In all other case, Boost.Build will convert "." into directory where it occurs.
Under certain conditions, an attempt is made to cache results of transformation search. First, the sources are replaced with targets with special name and the found target list is stored. Later, when properties, requested type, and source type are the same, the store target list is retrieved and cloned, with appropriate change in names.