You wish to use Boost.Build to build a dynamic library from a collection of C++ source files, such as those listed in Example 1-2.
Create a Jamroot file in the directory where you
wish the dynamic library—and the import library, if any—to be created. In the file
Jamroot, invoke the lib
rule to declare a library target,
specifying your .cpp files as sources and the
properties <link>shared
as a requirement. Add a
usage requirement of the form <include>
path
to specify the library’s
include directory, i.e., the directory with respect to which include
directives for library headers should be resolved. If your source
files include headers from other libraries, you may need to add several requirements of
the form <include>
path
to tell the compiler where to search for included headers. You may also need to add one or
more requirements of the form <define>
symbol
to ensure that your dynamic
library’s symbols will be exported using _
_declspec(dllexport)
on Windows. Finally, run bjam from the directory containing Jamroot, as described in Recipe
1.7.
For example, to build a dynamic library from the source files listed in Example 1-2, create a file named Jamroot in the directory georgeringo, as shown in Example 1-12.
Example 1-12. A Jamfile to build the dynamic library georgeringo.so, georgeringo.dll, or georgeringo.dylib
# Jamfile for project georgringo lib libgeorgeringo : # sources george.cpp ringo.cpp georgeringo.cpp : # requirements <link>shared <define>GEORGERINGO_DLL : # default-build : # usage-requirements <include>.. ;
To build the library, enter:
> bjam libgeorgeringo
As discussed in Recipe 1.8, the lib
rule is used to
declare a target representing a static or dynamic library. The usage requirement <include>.
. frees projects which depend on your library
from having to explicitly specify your library’s include directory in their requirements.
The requirement <link>shared
specifies that the
target should always be built as a dynamic library. If you want the freedom to build a
library target either as static or as dynamic, you can omit the requirement <link>shared
and specify this property on the command
line, or in the requirements of a target that depends on the library target. Writing a
library which can be built as either static or dynamic requires some care, however,
because of the preprocessor directives necessary to ensure that symbols are properly
exported on Windows. Rewriting Example 1-2 so that it can be built as either static or
dynamic makes a good exercise.
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