[lldb-dev] When should ArchSpecs match?

[Zachary Turner via lldb-dev]

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 at 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 at 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
> > _______________________________________________
> > lldb-dev mailing list
> > lldb-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>
> _______________________________________________
> lldb-dev mailing list
> lldb-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/lldb-dev/attachments/20181206/7f81a363/attachment.html>