There is genuinely no OS in some cases, like people who debug the software that
runs in a keyboard or a mouse. And to higher-level coprocessors in a modern
phones; the SOCs on all these devices have a cluster of processors, and only
some of them are running an identifiable operating system, like iOS or Android.
I'll be honest, it's not often that we'll be debugging an arm64-apple-none
target and have to decide whether an arm64-apple-ios binary should be loaded or
not. But we need some way to express this kind of environment.
> On Dec 6, 2018, at 3:50 PM, Zachary Turner <ztur...@google.com> wrote:
>
> Is there some reason we can’t define vendors, environments, arches, and oses
> for all supported use cases? That way “there is no os” would not ever be a
> thing.
> On Thu, Dec 6, 2018 at 3:37 PM Jason Molenda via lldb-dev
> <lldb-dev@lists.llvm.org> wrote:
> I think the confusing thing is when "unspecified" means "there is no OS" or
> "there is no vendor" versus "vendor/OS is unspecified".
>
> Imagine debugging a firmware environment where we have a cpu arch, and we may
> have a vendor, but we specifically do not have an OS. Say armv7-apple-none
> (I make up "none", I don't think that's valid). If lldb is looking for a
> binary and it finds one with armv7-apple-ios, it should reject that binary,
> they are incompatible.
>
> As opposed to a triple of "armv7-*-*" saying "I know this is an armv7 system
> target, but I don't know anything about the vendor or the OS" in which case
> an armv7-apple-ios binary is compatible.
>
> My naive reading of "arm64-*-*" means vendor & OS are unspecified and should
> match anything.
>
> My naive reading of "arm64" is that it is the same as "arm64-*-*".
>
> I don't know what a triple string looks like where we specify "none" for a
> field. Is it armv7-apple-- ? I know Triple has Unknown enums, but "Unknown"
> is ambiguous between "I don't know it yet" versus "It not any Vendor/OS".
>
> Some of the confusion is the textual representation of the triples, some of
> it is the llvm Triple class not having a way to express (afaik) "do not match
> this field against anything" aka "none".
>
>
>
> > On Dec 6, 2018, at 3:19 PM, Adrian Prantl via lldb-dev
> > <lldb-dev@lists.llvm.org> wrote:
> >
> > I was puzzled by the behavior of ArchSpec::IsExactMatch() and
> > IsCompatibleMatch() yesterday, so I created a couple of unit tests to
> > document the current behavior. Most of the tests make perfect sense, but a
> > few edge cases really don't behave like I would have expected them to.
> >
> >> {
> >> ArchSpec A("arm64-*-*");
> >> ArchSpec B("arm64-apple-ios");
> >> ASSERT_FALSE(A.IsExactMatch(B));
> >> // FIXME: This looks unintuitive and we should investigate whether
> >> // this is the desired behavior.
> >> ASSERT_FALSE(A.IsCompatibleMatch(B));
> >> }
> >> {
> >> ArchSpec A("x86_64-*-*");
> >> ArchSpec B("x86_64-apple-ios-simulator");
> >> ASSERT_FALSE(A.IsExactMatch(B));
> >> // FIXME: See above, though the extra environment complicates things.
> >> ASSERT_FALSE(A.IsCompatibleMatch(B));
> >> }
> >> {
> >> ArchSpec A("x86_64");
> >> ArchSpec B("x86_64-apple-macosx10.14");
> >> // FIXME: The exact match also looks unintuitive.
> >> ASSERT_TRUE(A.IsExactMatch(B));
> >> ASSERT_TRUE(A.IsCompatibleMatch(B));
> >> }
> >>
> >
> > Particularly, I believe that:
> > - ArchSpec("x86_64-*-*") and ArchSpec("x86_64") should behave the same.
> > - ArchSpec("x86_64").IsExactMatch("x86_64-apple-macosx10.14") should be
> > false.
> > - ArchSpec("x86_64-*-*").IsCompatibleMath("x86_64-apple-macosx") should be
> > true.
> >
> > Does anyone disagree with any of these statements?
> >
> > I fully understand that changing any of these behaviors will undoubtedly
> > break one or the other edge case, but I think it would be important to
> > build on a foundation that actually makes sense if we want to be able to
> > reason about the architecture matching logic at all.
> >
> > let me know what you think!
> > -- adrian
> > _______________________________________________
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> > lldb-dev@lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>
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