The compile property allows component developers to specify source files which should be compiled and added to one of the target libraries. Usually each source file will end up the library libtarget.a. It is possible for component writers to specify an alternative library for an entire package using the library property. Alternatively the desired library can be specified on the compile line itself. For example, to add a particular source file to the libextras.a library the following could be used:
cdl_package CYGPKG_IO_SERIAL {
…
compile -library=libextras.a common/tty.c
} |
Details of the build process including such issues as compiler flags and the order in which things happen can be found in Chapter 4.
compile properties can occur in any of cdl_option, cdl_component, cdl_package or cdl_interface. A compile property has effect if and only if the entity that contains it is active and enabled. Typically the body of a cdl_package will define any source files that need to be built irrespective of individual options, and each cdl_component, cdl_option, and cdl_interface will define source files that are more specific. A single compile property can list any number of source files, all destined for the same library. A cdl_option or other entity can contain multiple compile properties, each of which can specify a different library. It is possible for a given source file to be specified in compile properties for several different options, in which case the source file will get built if any of these options are active and enabled.
If the package follows the directory layout conventions then the configuration tools will search for the specified source files first in the src subdirectory of the package, then relative to the package directory itself.
Note: A shortcoming of the current specification of compile properties is that there is no easy way to specify source files that should be built unless an option is enabled. It would sometimes be useful to be able to say: “if option A is enabled then compile file x.c, otherwise compile file y.c. There are two simple ways of achieving this:
Always compile y.c, typically by listing it in the body of the cdl_package, but use #ifndef A to produce an empty object file if option A is not enabled. This has the big disadvantage that the file always gets compiled and hence for some configurations builds will take longer than necessary.
Use a calculated option whose value is !A, and have a compile y.c property in its body. This has the big disadvantage of adding another calculated option to the configuration.
It is likely that this will be resolved in the future, possibly by using some sort of expression as the argument to a compile property.
Note: Currently it is not possible to control the priority of a compile property, in other words the order in which a file gets compiled relative to other build steps. This functionality might prove useful for complicated packages and should be added.
cdl_package CYGPKG_INFRA {
display "Infrastructure"
include_dir cyg/infra
description "
Common types and useful macros.
Tracing and assertion facilities.
Package startup options."
compile startup.cxx prestart.cxx pkgstart.cxx userstart.cxx \
dummyxxmain.cxx memcpy.c memset.c delete.cxx \
diag.cxx tcdiag.cxx
} |