path: root/NEWS

Version 0.4.0

  * Support for Windows.

    The toolchain can now be built and used on Windows with either MSVC or
    MinGW GCC.

    With VC, the toolchain can be built with version 14 Update 2 or later and
    used with any version from 13. /MD and, for C++, /EHsc are default but are
    overridden if an explicit value is specified in the coptions variable.

  * Support for C compilation.

    There is now the 'c' module in addition to 'cxx' as well as 'cc', which
    stands for C-common. Mixed source (C and C++) building is also supported.

  * Integration with pkg-config.

    Note that build2 doesn't use pkg-config to actually locate the libraries
    (because this functionality of pkg-config is broken when it comes to
    cross-compilation). Rather, it searches for the library (in the
    directories extracted from the compiler) itself and then looks for the
    corresponding .pc file (normally in the pkgconfig/ subdirectory of where
    it found the library). It then calls pkg-config to extract any additional
    options that might be needed to use the library from this specific .pc
    file.

  * Initial support for library versioning.

    Currently, only platform-independent versions are supported. They get
    appended to the library name/soname. For example:

    lib{foo}: bin.lib.version = @-1.2

    This will produce libfoo-1.2.so, libfoo-1.2.dll, etc.

    In the future the plan is to support platform-specific versions, for
    example:

    lib{foo}: bin.lib.version = linux@1.2.3 freebsd@1.2 windows@1.2

  * Library dependency export support.

    In build2 a library dependency on another library is either an "interface"
    or "implementation". If it is an interface, then everyone who links this
    library should also link the interface dependency, explicitly. A good
    example of an interface dependency is a library API that is called in an
    inline function.

    Interface dependencies of a library should be explicitly listed in the
    *.export.libs variable (where we can now list target names). The typical
    usage will be along these lines:

    import int_libs  = libformat%lib{format}
    import int_libs += ...

    import imp_libs  = libprint%lib{print}
    import imp_libs += ...

    lib{hello}: ... $imp_libs $int_libs

    lib{hello}: cxx.export.libs = $int_libs

    There is support for symbol exporting on Windows and build2 now also does
    all the right things when linking static vs shared libraries with regards
    to which library dependencies to link, which -rpath/-rpath-link options to
    pass, etc.

  * Support for the uninstall operation in addition to install.

  * Support for preserving subdirectories when installing.

    This is useful, for example, when installing headers:

    install.include = $install.include/foo/
    install.include.subdirs = true

    The base for calculating the subdirectories is the scope where the subdirs
    value is set.

  * Support for installing as a different file name.

    Now the install variable is a path, not dir_path. If it is a directory
    (ends with a trailing slash), then the target is installed into this
    directory with the same name. Otherwise, the entire path is used as the
    installation destination.

  * Support for config.bin.{,lib,exe}.{prefix,suffix}.

    This replaces the bin.libprefix functionality.

  * Support for global config.install.{cmd,options,sudo,mode,dir_mode}.

    This way we can do:

    b install \
      config.install.data_root=/opt/data \
      config.install.exec_root=/opt/exec \
      config.install.sudo=sudo

  * The new -V option is an alias for --verbose 3 (show all commands).

  * Support for specifying directories in config.dist.archives.

    For example, this command will create /tmp/foo-X.Y.Z.tar.xz:

    b foo/ config.dist.archives=/tmp/tar.xz

  * The cxx (and c) module is now project root-only.

    This means these modules can only be loaded in the project root scope
    (normally root.build). Also, the c.std and cxx.std values must now be set
    before loading the module to take effect.

  * The test, dist, install, and extension variables now have target
    visibility to prevent accidental "reuse" for other purposes.

  * An empty config.import.* value is now treated as an instruction to skip
    subproject search. Also, explicit config.import.* values now take
    precedence over the subproject search.

  * Search for subprojects is no longer recursive. In the future the plan is
    to allow specifying wildcard paths (* and **) in the subprojects variable.

  * Support out-qualified target syntax for setting target-specific variables
    on targets from src_base. For example:

    doc{INSTALL}@./: install = false

  * Only "effective escaping" (['"\$(]) is now performed for values on the
    command line. This makes for a more usable interface on Windows provided
    we use "sane" paths (no spaces, no (), etc).

  * The default variable override scope has been changed from "projects and
    subprojects" to "amalgamation".

    The "projects and subprojects" semantics resulted in counter-intuitive
    behavior. For example, in a project with tests/ as a subproject if one
    builds one of the tests directly with a non-global override (say C++
    compiler), then the main project would be built without the overrides. In
    this light, overriding in the whole amalgamation seems like the right
    thing to do. The old behavior can still be obtained with explicit scope
    qualification, for example:

    b ./:foo=bar

  * The config.build format has been made more readable. Specifically, the
    order is now from the higher-level modules (e.g., c, cxx) to the
    lower-level (e.g., binutils) with imports coming first. The file now also
    includes an explicit version for incompatibility detected/migration in
    the future.

  * Support for <, >, <=, >= in the eval context.

    Now we can write:

    if ($build.version >= 40000)

  * Support for single line if-blocks.

    Now we can write:

    if true
      print true
    else
      print false

    Instead of having to do:

    if true
    {
      print true
    }
    else
    {
      print false
    }

  * Support for prepend/append in target type/pattern-specific variables.

    Semantically, these are similar to variable overrides and are essentially
    treated as "templates" that are applied on lookup to the "stem" value that
    is specific to the target type/name. For example:

    x = [string] a
    file{f*}: x =+ b

    sub/:
    {
      file{*}: x += c

      print $(file{foo}:x)  # abc
      print $(file{bar}:x)  # ac
    }

  * The obj*{} target type to exe/lib mapping has been redesigned.

    Specifically:

    - objso{} and libso{} target types have been renamed to objs{} and libs{}

    - obje{} has been added (so now we have obje{}, obja{}, and objs{})

    - obje{} is now used for building exe{}

    - object file extensions now use "hierarchical extensions" that reflect
      the extension of the corresponding exe/lib target (instead of the -so
      suffix we used), specifically:

      obje{}: foo.o, (UNIX), foo.exe.o (MinGW), foo.exe.obj (MSVC)
      obja{}: foo.a.o (UNIX, MinGW), foo.lib.obj (MSVC)
      objs{}: foo.so.o (UNIX), foo.dylib.o (Darwin), foo.dll.o (MinGW),
              foo.dll.obj (MSVC)

    We now also have libi{} which is the Windows DLL import library. When
    used, it is the first ad hoc group member of libs{}.

Version 0.3.0

  * Support for High Fidelity Builds (HFB).

    The C++ compile and link rules now detect when the compiler, options, or
    input file set have changed and trigger the update of the target. Some
    examples of the events that would now trigger an automatic update are:

    * compiler change (e.g., g++ to clang++), upgrade, or reconfiguration
    * change of compile/link options (e.g., -O2 to -O3)
    * replacement of a source file (e.g., foo.cpp with foo.cxx)
    * removal of a file from a library/executable

  * New command line variable override semantics. A command line variable can
    be an override (=), prefix (=+), or suffix (+=), for example:

    b config.cxx=clang++ config.cxx.coptions+=-g config.cxx.poptions=+-I/tmp

    Prefixes/suffixes are applied at the outsets of values set in buildfiles,
    provided these values were set (in those buildfiles) using =+/+= and not
    an expansion, for example:

    b x=+P x+=S

    x = y
    print $x # P y S

    x =+ p
    x += s
    print $x # P p y s S

    But:

    x = A $x B
    print $x # A P p y s S B

    By default an override applies to all the projects mentioned in the
    buildspec as well as to their subprojects. We can restrict an override to
    not apply to subprojects by prefixing it with '%', for example:

    b %config.cxx=clang++ configure

    An override can also be made global (i.e., it applies to all projects,
    including the imported ones) by prefixing it with '!'. As an example,
    compare these two command lines:

    b config.cxx.coptions+=-g
    b '!config.cxx.coptions+=-g'

    In the first case only the current project and its subprojects will be
    recompiled with the debug information. In the second case, everything that
    the current project requires (e.g., imported libraries) will be rebuilt
    with the debug information.

    Finally, we can also specify the scope from which an override should
    apply. For example, we may only want to rebuild tests with the debug
    information:

    b tests/:config.cxx.coptions+=-g

  * Attribute support. Attributes are key or key=value pairs enclosed in []
    and separated with spaces. They come before the entity they apply to.
    Currently we recognize attributes for variables and values. For variables
    we recognize the following keys as types:

    bool
    uint64
    string
    path
    dir_path
    abs_dir_path
    name
    strings
    paths
    dir_paths
    names

    For example:

    [uint64] x = 01
    print $x # 1
    x += 1
    print $x # 2

    Note that variable types are global, which means you could type a variable
    that is used by another project for something completely different. As a
    result, typing of values (see below) is recommended over variables. If you
    do type a variable, make sure it has a namespace (typing of unqualified
    variables may become illegal).

    For values we recognize the same set of types plus 'null'. The value type
    is preserved in prepend/append (=+/+=) but not in assignment. For example:

    x = [uint64] 01
    print $x # 1
    x += 1
    print $x # 2

    x = [string] 01
    print $x # 01
    x += 1
    print $x # 011

    x = [null]
    print $x # [null]

    Value attributes can also be used in the evaluation contexts, for example:

    if ($x == [null])

    if ([uint64] $x == [uint64] 0)

  * Support for scope/target-qualified variable expansion. For example:

    print $(dir/:x)
    print $(file{target}:x)
    print $(dir/file{target}:x)

  * Command line options, variables, and buildspec can now be specified in any
    order. This is especially useful if you want to re-run the previous
    command with -v or add a forgotten config variable:

    b test -v
    b configure config.cxx=clang++

  * Support for the Intel C++ compiler on Linux.

  * Implement C++ compiler detection. Currently recognized compilers and their
    ids (in the <type>[-<variant>] form):

      gcc            GCC
      clang          Vanilla Clang
      clang-apple    Apple Clang (and the g++ "alias")
      icc            Intel icpc
      msvc           Microsoft cl.exe

    The compiler id, version, and other information is available via the
    following build system variables:

    cxx.id
    cxx.id.{type,variant}
    cxx.version
    cxx.version.{major,minor,patch,build}
    cxx.signature
    cxx.checksum
    cxx.target
    cxx.target.{cpu,vendor,system,version,class}

  * Implement ar/ranlib detection. The following information is available
    via the build system variables:

    bin.ar.signature
    bin.ar.checksum
    bin.ranlib.signature
    bin.ranlib.checksum

  * On update for install the C++ link rule no longer uses the -rpath
    mechanism for finding prerequisite libraries.

  * Set build.host, build.host.{cpu,vendor,system,version,class} build system
    variables to the host triplet. By default it is set to the compiler target
    build2 was built with but a more precise value can be obtained with the
    --config-guess option.

  * Set build.version, build.version.{major,minor,patch,release,string} build
    system variables to the build2 version.

  * Extracted header dependencies (-M*) are now cached in the auxiliary
    dependency (.d) files rather than being re-extracted on every run. This
    speeds up the up-to-date check significantly.

  * Revert back to only cleaning prerequisites if they are in the same project.

    Cleaning everything as long as it is in the same strong amalgamation had
    some undesirable side effects. For example, in bpkg, upgrading a package
    (which requires clean/reconfigure) led to all its prerequisites being
    cleaned as well and then rebuilt. That was surprising, to say the least.

  * Allow escaping in double-quoted strings.

  * Implement --buildfile option that can be used to specify the alternative
    file to read build information from. If '-' is specified, read from STDIN.

  * New scoping semantics. The src tree paths are no longer entered into the
    scope map. Instead, targets from the src tree now include their out tree
    directories (which are, in essence, their "configuration", with regards to
    variable lookup). The only user-visible result of this change is the extra
    '@<out-dir>/' suffix that is added when a target is printed, for example,
    as part of the compilation command lines.

Version 0.2.0

  * First public release.