On Mon, Feb 6, 2017 at 4:50 AM, Panu Matilainen <[email protected]> wrote: > On 02/06/2017 10:56 AM, Vít Ondruch wrote: >> >> >> >> Dne 3.2.2017 v 13:14 Panu Matilainen napsal(a): >>> >>> >>> Stunned silence on rpm-maint, forwarding to rpm-ecosystem in hopes of >>> a larger and livelier audience... >>> >>> - Panu - >>> >>> -------- Forwarded Message -------- >>> Subject: [Rpm-maint] Fixing macro scoping >>> Date: Mon, 23 Jan 2017 12:30:21 +0200 >>> From: Panu Matilainen <[email protected]> >>> To: [email protected] <[email protected]> >>> >>> >>> Consider the following snippet, originating from >>> https://bugzilla.redhat.com/show_bug.cgi?id=552944: >>> >>> %{!?foo: %define foo bar} >>> %define dofoo() true >>> echo 1: %{foo} >>> %dofoo >>> echo 2: %{foo} >>> >>> I'd assume everybody agrees both %{foo}'s should evaluate to the same >>> value, but that is not the case currently. Using a cli-variant of the >>> above: >>> >>> [pmatilai@sopuli rpm]$ rpm --define 'dofoo() true' --eval '%{!?foo: >>> %define foo bar}' --eval '%foo' --eval '%dofoo' --eval '%foo' >>> warning: Macro %foo defined but not used within scope >>> >>> bar >>> true >>> %foo >>> >>> The flaw here is that rpm supposedly implements block level scoping >>> for macros (so in the above example, "foo" would only exist in the >>> {!?foo:...} block), but doesn't actually enforce that, unless a >>> parametric macro is "called". Current rpm warns about it, but warnings >>> or not this behavior doesn't make the slightest sense. >>> >>> The question is, what do you think %{foo} should evaluate to in this >>> case? >>> >>> Fixing it to honor the strict "block scoping" concept is not hard, now >>> that the scoping level is honored from Lua too (see >>> >>> https://github.com/rpm-software-management/rpm/commit/1767bc4fd82bfacee622e698f9f0ae42c02126fa). >>> In this case the above reproducer would emit >>> >>> %foo >>> true >>> %foo >> >> >> As far as I can tell, usage of %define is discouraged and I never really >> understood why. But this example explains it and this should be the >> right behavior IMO. > > > Yup, people are told to avoid %define like it was the plague, which is just > plain bullsh**. You just need to understand the scoping of macros. Which > almost nobody does, no matter how many times it gets repeated here or there. > That the rpm implementation of the scoping is very buggy doesn't exactly > help of course. > > So I've really started thinking it's better to make rpm behave the way > people expect it to instead of banging my head against this for another 10+ > years. >
For what it's worth, Andreas Scherer's debbuild[1] treats %define just like %global in terms of scope, which I guess is the expectation of most people (though that might be because it's not exactly well documented that there *are* rules for %define scoping). That said, if the scoping rules are clear (and work as they're supposed to!), I don't see a reason why not to actually have scoping for %define. [1]: https://github.com/ascherer/debbuild -- 真実はいつも一つ！/ Always, there's only one truth! _______________________________________________ Rpm-ecosystem mailing list [email protected] http://lists.rpm.org/mailman/listinfo/rpm-ecosystem
