[cfe-dev] Adding indexing support to Clangd

[Alex L via cfe-dev]

On 15 August 2017 at 07:57, Vladimir Voskresensky via cfe-dev <
cfe-dev at lists.llvm.org> wrote:

>
>
> On 14.08.2017 11:06, Ilya Biryukov wrote:
>
> Could you provide more info, please.
>> Are USRs different for same named file-local entries (i.e. static
>> functions)?
>>
>
> Looking at USRGenerator::VisitVarDecl, it seems they will be the same
> across different translation units.
> For local entities, "location" is part of the USR.  ("Location" is a
> filename + an offset from the start of that file).
>
> That was my point, U in USRs are not so Unified, so can not be used as
> universal keys for queries in DB.
> Adding location to USR makes them less usable in index if fast incremental
> re-index is going to be implemented vs. full reparse on each change.
>
> Vladimir.
>

U is meant to be unique. USRs file-local declarations like static functions
will include the filename only. USRs for function-local declarations will
also include the offset in the file, but they're not actually indexed.
There are a couple of global declarations that include file + offset in the
USR as well - ObjC class extensions, some embedded tag decls (not that
common), template parameter names (not actually indexed) & macros (not
indexed).

What exactly prevents unique strings from being used as keys for queries?

Are filenames are a problem for the incremental re-indexing? If they
aren't, then there are probably way to work around the file offsets in USRs
for the incremental re-indexing, especially given how uncommon they
actually are.

Alex

>
> --
> Regards,
> Ilya Biryukov
>
>
>
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