$NetBSD: BUILDLINK3_DG,v 1.5 2004/07/30 20:52:44 jlam Exp $ 0 Developer's guide to buildlink3 ================================= This is a tutorial for pkgsrc developers to understand and to use the buildlink3 framework in pkgsrc. 1 Changes between buildlink2 and buildlink3 =========================================== The buildlink3 framework is a evolutionary descendant of the buildlink2 framework that does a better job of adhering to the fundamental buildlink principle: only allow the software build process to see what we choose to allow it to see. 1.1 Better behavior with libtool ================================ One of the biggest problems in buildlink2 is handling packages that install libtool archive files for libraries that are also present in the base system. buildlink3 is significantly better at this as it more tightly controls where libtool can find libtool archives. One side effect of this is that we no longer need to create fake libtool archives to work around cases where the pkgsrc libraries were being used instead of the system libraries if they shared the same name. 1.3 Support for native compilers ================================ The buildlink3 wrapper scripts have better support for using SunPro and MIPSpro compilers to build pkgsrc software. For the most part, packages can use any compiler, but some third-party software is written assuming that it will be compiled using GCC. The buildlink3 wrapper scripts can capture some common GCC options and convert them into native toolchain equivalents. 1.4 New buildlink3.mk file structure ==================================== buildlink3.mk files have two major differences over buildlink2.mk files. The first, most noticeable difference is that buildlink3.mk generally don't contain a BUILDLINK_FILES definition. This is because buildlink3 automatically determines which files to symlink into ${BUILDLINK_DIR} by examining the PLIST of the installed package. The second difference is that buildlink3.mk files keep track of how "deep" we are in including buildlink3.mk files, and only creates dependencies on packages encountered at depth 1. This means that packages that want to add a dependency must directly include the buildlink3.mk file for that dependency. 1.5 Support for pkgviews ======================== When building pkgviews packages, buildlink3 doesn't symlink files into ${BUILDLINK_DIR} since it can safely refer to only a specific package's files by passing the appropriate -I and -L flags to the compiler, where points to a location in the package's depot directory. When building "overwrite" packages, buildlink3 will act and feel very much like buildlink2 but with more advanced wrapper scripts, and there are provisions for allowing an "overwrite" package to build against the viewed instance of a depoted package. 2 Troubleshooting ================= Q1: I'm trying to bl3ify a package but I get an error that looks like: make: don't know how to make _BUILDLINK_USE. Stop A1: You forgot to change a reference to a buildlink2.mk file into a buildlink3.mk file. Q2: Dependencies are added for every single buildlink3.mk file I include, including for when it's supposed to use the base system software. What's going on? A2: You forgot to change USE_BUILDLINK2 to USE_BUILDLINK3 in the package Makefile. Q3: Where can I see the actual command executed by the wrapper scripts? A3: You should examine the contents of the ${WRKDIR}/.work.log file. The lines preceded with [*] are the commands that are intercepted by the wrapper scripts, and the lines preceded with <.> are the commands that are executed by the wrapper scripts. Q4: Why can't I check the values of variables set by the buildlink3 framework using 'make show-var VARNAME=...'? A4: Some buildlink3 variables are only defined for a subset of a package build phases. Try instead: make show-var PKG_PHASE=buildlink VARNAME=...'