On Tuesday 13 October 2015 13:54:31 Richard W.M. Jones wrote: > In the referenced bug, a customer had installed a web browser called > 'palemoon'. The RPM of this web browser provides and requires various > core libraries, such as: > > Provides: libnss3.so()(64bit) # normally provided by 'nss' > Requires: libxul.so()(64bit) # normally provided by 'firefox' > > Our previous algorithm -- inherited from the days when we used to run > 'rpm' commands -- takes every provider of a particular requirement and > adds it to a big list, so if any other package requires > 'libnss3.so()(64bit)', then both 'nss' and 'palemoon' are added to the > package list. > > Yum used to handle this differently - it used to only pick the package > with the shortest name. Later on, before yum was retired, it had a > more complex decision algorithm described here: > http://yum.baseurl.org/wiki/CompareProviders > > This change makes supermin use the shortest name algorithm, so in the > case above, it always picks 'nss' over 'palemoon'. > > There is a second possible problem which is not fixed by the current > patch set: If a package both provides and requires the same > dependency, we should ignore that dependency. For example, 'palemoon' > both Provides and Requires 'libxul.so()(64bit)', so if 'palemoon' is > pulled in, then 'firefox' would not be an additional requirement. > Because we store all the packages in a big list, we lose track of > where a dependency originates from, so it is not easy to implement > this second change. > --- > src/rpm.ml | 55 +++++++++++++++++++++++++++++++++++++++---------------- > 1 file changed, 39 insertions(+), 16 deletions(-) > > diff --git a/src/rpm.ml b/src/rpm.ml > index 4d31472..d3ab7da 100644 > --- a/src/rpm.ml > +++ b/src/rpm.ml > @@ -210,8 +210,42 @@ let rpm_package_name pkg = > let rpm_get_package_database_mtime () = > (lstat "/var/lib/rpm/Packages").st_mtime > > -(* Memo of resolved provides. *) > -let rpm_providers = Hashtbl.create 13 > +(* Return the best provider of a particular RPM requirement. > + * > + * There may be multiple, or no providers. In case there are multiple, > + * choose the one with the shortest name (as yum used to). > + * > + * We could do better here: http://yum.baseurl.org/wiki/CompareProviders > + *) > +let provider = > + (* Memo of resolved provides. *) > + let rpm_providers = Hashtbl.create 13 in > + fun req -> > + try Hashtbl.find rpm_providers req > + with Not_found -> > + try > + (* 'providers' here is an array of just package names. *) > + let providers = rpm_pkg_whatprovides (get_rpm ()) req in > + let providers = Array.to_list providers in > + (* --whatprovides will return duplicate identical packages, so: *) > + let providers = sort_uniq providers in > + match providers with > + |  -> None > + | [name] -> Some name > + | names -> > + if !settings.debug >= 2 then > + printf "supermin: rpm: multiple providers: requirement %s: providers: %s\n" > + req (String.concat " " names); > + let cmp name1 name2 = > + let len1 = String.length name1 and len2 = String.length name2 in > + if len1 <> len2 then compare len1 len2 > + else compare name1 name2 in > + let names = List.sort cmp names in > + let best_name = List.hd names in > + if !settings.debug >= 2 then > + printf "supermin: rpm: multiple providers: picked %s\n" best_name; > + Some best_name > + with Not_found -> None This is nicer indeed, although there are two issues: - the caching of providers (rpm_providers) is not done, so it will do the search every time (and things like "/bin/sh provided by bash" appear a lot in packages) - the old code was checking each provided name was really a package (using rpm_package_of_string). The new code should then pick the first one in the list that is actually installed (i.e. with a Some result of rpm_package_of_string); the two cases | + | [name] -> Some name | + | names -> could be joined together, printing the debug output only if there is more than one element. I hope List.sort on one element should be a no-op... Thanks, -- Pino Toscano
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