[llvm] r355646 - Work around a module build error on the LLDB incremental green dragon bot.

[David Blaikie via llvm-commits]

On Mon, Mar 11, 2019 at 3:04 PM Adrian Prantl <aprantl at apple.com> wrote:

>
> On Mar 11, 2019, at 2:09 PM, David Blaikie <dblaikie at gmail.com> wrote:
>
>
>
> On Mon, Mar 11, 2019 at 2:01 PM Adrian Prantl <aprantl at apple.com> wrote:
>
>> You'll see the sad resolution of this two commits further down. (I
>> reverted this one, too). There was a header file with a function body that
>> used the LLVM_DEBUG macro (which I believe fundamentally cannot work inside
>> a non-textual header)
>>
>
> Right - if it depends on its inclusion state to define DEBUG_TYPE that's
> not modular. I assume that's the case? Oh, it looks like it is the case,
> that DEBUG_TYPE is defined within this file, so I don't think there's a
> problem with using LLVM_DEBUG here? It's not intended to consume the value
> of DEBUG_TYPE from its inclusion context.
>
>
> Oh, I had missed that it did define its own DEBUG_TYPE.
>
>
> Perhaps that's invalid in a modular context if it's ever included
> somewhere that also defines DEBUG_TYPE? I'm not sure there.
>
>
>> and inside of it it called a dump method, thus pulling the reference to
>> the dump method into the link.
>>
>
> Missed a step here - inside of what it called a dump function? & why was
> that a problem? It called a dump function unconditionally rather than only
> under the condition that the dump function is defined? I'm not sure how
> modules would make/break that.
>
>
> Perhaps the LLVM_DEBUG macro is a red herring then and just the presence
> of the dump() function in the function body was enough to produce the
> dependency on the dump function. The linker error was that that dump()
> method was an undefined symbol while linking llvm-lto.
>

I'm still not sure I follow how the modularity of this file would be
related to this problem - can you explain it in further detail, to make
sure we're fixing this in the right way/tracking any other bugs this might
be indicative of?


>
> -- adrian
>
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