[cfe-dev] Cross Translation Unit Support in Clang

[Noah L via cfe-dev]

On Thu, Jun 29, 2017 at 10:31 PM, Manuel Klimek <klimek at google.com> wrote:
...

>
>> I'm not saying it's not feasible. I'm not even saying it's not
>> reasonable. But you can see why it'd be nicer for me if libTooling could
>> just present me with a combined AST. :)
>>
>
> Unfortunately that only scales to small projects in the generalized case.
> The static analyzer gets away with it because it only loads things close to
> the function it analyzes, instead of needing a global view.
>

Scales in what way? Memory usage? I just watched Gabor's talk where, if I
understood correctly, he mentions that the combined ASTs for llvm took up
40Gb when exported to disk. I'm assuming that's not compressed or anything.
There are plenty of workstations with 40Gb+ of RAM. The static analyzer may
need significant additional memory for its processing, but my tool does not.

And tools like mine aren't part of the interactive development process.
They may only ever need to be applied to a project once. So it might even
be acceptable for it to take a week or whatever to execute. (I don't see
why this wouldn't apply, to a lesser degree, to the static analyzer as
well.)

Are you sure you're not being overly conservative about the scaling issue?
Or am I somehow just being naive here? For me, I feel that it's a very
inconvenient feature omission, and I'm not sure I really understand the
reluctance.

Anyway, if I understood correctly, Gabor was implying that I could somehow
use/abuse the new feature to achieve a combined AST? By importing all the
functions in the other translation units manually? And if memory use really
is an issue, is there a way to import a function into the AST, check it
out, then lose it when your done with it?

Noah
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/cfe-dev/attachments/20170630/bd6dee91/attachment.html>