From: hf_pabst (hfp_at_[hidden])
Date: 2005-06-24 09:01:29
Hello,
is there any need for an extended lib rule? My personal use-case will
be described here...
At the end, a little bit jam code will follow...
---
Export/import symbols into/from a DLL without the need of a top-level
header.
Such a typical header is now (logically) moved into the build system.
Exporting becomes naturally a 'requirement' and importing will be
an 'usage-requirement'.
In case of more than one component (dll) per main-projects with inter-
dependencies, that mean importing and exporting symbols for a single
component at the same time, you can't have a simple control header
that says 'dllexport' or(!) 'dllimport'. It's needed to tag each
component with an own (unique) symbol. Now you have
dllexport/dllimport per component (symbol).
This 'dll.lib' rule provides the standard to use the target name
(uppercase) as symbol for the preprocessor and define it
automatically with dllexport, dllimport or nothing (link static). The
target name should always unique per component. Everything that needs
to be exported/imported is named (tagged) naturally with the
component name, i.e: class LIBMYCOMPONENT my_type { ... };
The 'dll.lib' rule use the original 'lib' rule and provides the same
arguments and argument order. If you need a symbol name that isn't
derived from the target name, you can use the optional 6'th argument
to define an own symbol.
If you hold helper jamfiles in a local directory you only need one
statement, i.e.:
import build/dll : lib ;
in your top-level jamfile ("the project") before any targed
definition, where './build' contain this file ('dll.jam'). The 'lib'
option after the colon prevents you from writing:
dll.lib ...
Now you can use an unqualified dll.lib (without dll):
lib ...
This is like a replacement of the built-in 'lib' rule.
---- jam code ---
rule lib ( names + : sources * : requirements * : default-build * :
usage-requirements * : symbol ? )
{
echo $(names)": using extended version of 'lib' rule" ;
if ! $(symbol)
{
# By default use the uppercase name
symbol = $(names:U) ;
}
import os ;
if [ os.on-windows ]
{
requirements +=
<link>shared:<define>$(symbol)=__declspec(dllexport)
<link>static:<define>$(symbol)="" ;
usage-requirements +=
<link>shared:<define>$(symbol)=__declspec(dllimport)
<link>static:<define>$(symbol)="" ;
}
else {
requirements += <define>$(symbol)="" ;
usage-requirements += <define>$(symbol)="" ;
}
import builtin : lib : builtin.lib ;
builtin.lib $(names) : $(sources) : $(requirements) : $(default-
build) : $(usage-requirements) ;
}