File Rules

• Usage
• Identifiers and Filenames

FileRule() creates a rule that creates files. This wraps the Toolset:File() convenience function discussed in Targets adding the ability to call the rule to create targets from buildfiles.

Usage

For example using FileRule to create a rule to archive object files into a static library. It uses FileRule() to create the rule and overrides depend() and build() but avoids having to add any boiler-plate code in create() to interact with the buildfile domain language:

local StaticLibrary = FileRule( 'StaticLibrary', gcc.static_library_filename );
StaticLibrary.build = gcc.archive;
StaticLibrary.depend = cc.static_library_depend;
toolset.StaticLibrary = StaticLibrary;

The StaticLibrary prototype is called from a buildfile to archive object files into a static library:

for _, cc in toolsets('^cc.*') do
    cc:StaticLibrary '${lib}/assert_${architecture}' {
        cc:Cc '${obj}/%1' {
            'assert.cpp'
        };
    };
end

Identifiers and Filenames

The second parameter to FileRule allows the identifier and filename of the created target to be overridden. The default, used when nothing is passed in the second parameter, uses Toolset.interpolate() to expand the identifier passed to create the target to use as both identifier and filename for the target. Otherwise the function passed in can return the identifier and filename for the target based on the toolset and identifier that is passed in.

For example gcc.static_library_filename() is implemented as:

function gcc.static_library_filename( toolset, identifier )
    local identifier = absolute( toolset:interpolate(identifier) );
    local filename = ('%s/lib%s.a'):format( branch(identifier), leaf(identifier) );
    return identifier, filename;
end