Date: Sat, 5 Jun 2010 23:46:05 +0000 From: "b. f." <bf1783@googlemail.com> To: Alexander Leidinger <Alexander@leidinger.net> Cc: freebsd-ports@freebsd.org Subject: Re: devel/gettext further update Message-ID: <AANLkTiksku-6-j_PsQZ52Hg5X7mCA__lZmlsYGex-Yen@mail.gmail.com> In-Reply-To: <20100605233128.0000011e@unknown> References: <AANLkTimTZuJ8hw9UIBloDCVSiHt680nofsbQiTSs2lD8@mail.gmail.com> <20100605233128.0000011e@unknown>
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On 6/5/10, Alexander Leidinger <Alexander@leidinger.net> wrote: ... >> >> Just for the record, the useful >> ports/Tools/scripts/explicit_lib_depends.sh, described and used in >> your link above, may _not_ find libraries that: >> >> -- are needed, but were intended to be statically linked; > > Correct. If you are of a way how to detect it after the fact, feel free > to share the info here. I don't think there is a good way to do this, but you could perhaps provide a warning about undefined symbols. > >> -- are needed, but loaded via dlopen(3) and friends (this is noted in >> a comment in ports/Tools/scripts/neededlibs.sh ); > > Correct. > > The goal for the scripts are to find entries for LIB_DEPENDS. A static > lib is a BUILD_DEPEND, not a LIB_DEPEND, and something which is opened I take your point. I was just mentioning possible problems with reference to the OP's use of your script to determine which ports to rebuild during an update. In that case, one may want to rebuild a dependent port after updating a static library, even if the dependent port may not be broken after the update. > via dlopen() is typically not a LIB_DEPEND but a RUN_DEPEND (it is the > other way around and the stuff which is dlopen()en depends upon what > is dlopen()ing it). Additionally if a something is using dlopen(), it I don't agree with this. Dependent ports often need to test for the presence of the libraries they intend to dlopen() during configuration or regression testing, or use headers from the ports that the libraries belong to during compilation. > should give sensible error messages when it does not work, so instead > of a cryptic error message which not everyone understands, there should > be (yes, I know, this is an idealistic POV) an error message even your > mother can understand. Well, let us say the average user. You don't know my mother. :) > I have to tell that those scripts are far from finished, the heuristic > of files to look at needs to be improved, and the translation into > ports-framework variable (like GNOME and X11 ones) needs to be written. > I didn't continue with this back when I was committing those scripts, > as the 3rd party software was far away from a state which would made it > really useful (indirect dependencies show up in runs of the scripts, > but they are not really welcome in our ports). > Yes, I didn't expect them to be highly polished. But they are already more elaborate than the rough, ad hoc methods I often use, anyway. >> -- are needed, and dynamically linked in the usual way, but are not >> referenced in any ELF DT_NEEDED tags. These tags are optional, not >> mandatory, in the System V ABI, and they can be missing for a number >> of reasons. They may not be present in a pre-compiled binary. Or, >> for example. because some ports make shared libraries by converting >> static archives into shared libraries with the linker, the tags can >> sometimes be missing for those libraries. Also, some ports use a >> version of gcc4* wired to devel/binutils, but then directly invoke >> some portion of the older base system binutils. I've seen this lead >> to missing tags in the past. > > Apart from the fact that I did not know that, do you know which ports in > the FreeBSD ports collection show this problem? Is there another way to > find this info in then? Well, these are admittedly uncommon cases, but I just thought I'd mention them in case someone using your script to determine which ports to update encountered one of them. With respect to the conversion of static libraries into shared libraries, anything that is using the '--whole-archive' flag during linking bears further examination. (It doesn't necessarily mean that the DT_NEEDED tags are missing, just that they _may_ be missing.) Among the ports that do this are older ports (often Fortran-related), or ports that once used static libraries because they were slightly more efficient, or more secure, but have since been modified to also build shared libraries in a very simple way: graphics/f90gl, math/arpack, math/atlas, math/blas, math/lapack, math/lapack95, math/metis, math/scalapack, math/spooles, math/suitesparse, etc. You can see the methods they use in the respective port Makefiles. Where needed, they may be fixed to include the proper tags, and I submitted patches to do this for some of them, but they were never committed, making linking for some of these libraries a real pain. See, for example, the unnecessarily complex (and wrong) description of how to link with the math/atlas _shared_ libraries in math/atlas/pkg-descr. As for ports that mix tool-chains, this includes a great many of the ports that USE_GCC=4.4+ or USE_FORTRAN, because, even though the gcc maintainer (finally) fixed the problem with the auto-detection of devel/binutils that could produce unpredictable results with respect to which tool-chain was used by the compiler in recent gcc snapshots, he did not also instruct those ports (and their dependencies) to use devel/binutils when invoking the tool-chain utilities _directly_, so they can (and do) mix tool-chains during some port builds. For example, the ports I mentioned above use lang/gcc44, which indirectly invokes the assembler and linker from devel/binutils, but then invoke the older base system linker directly in the port Makefiles. Apart from other problems that this can cause, I once noticed that this resulted in a loss of tags in the resulting binaries. The fact that such a loss can occur is obviously a bug, so I don't claim that this always happens, or that it happens with the current default setup. b.
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