[PATCH] D124635: Frontend: Delete output streams before closing CompilerInstance outputs

[Duncan P. N. Exon Smith via Phabricator via cfe-commits]

dexonsmith added a comment.

In D124635#3481346 <https://reviews.llvm.org/D124635#3481346>, @benlangmuir wrote:

> LGTM, although I made a suggestion about the spelling.

Thanks for the review!

>> This fixes theoretical bugs related to proxy streams, which may have
>> cleanups to run in their destructor. E.g., buffer_ostream supports
>> pwrite() by holding all content in a buffer until destruction time.
>
> The general point about streams with destructors is well taken, but it seems a bit broken that `buffer_ostream` cannot `flush`.  I guess the layering it just weird in that we have buffering in the base class, but `buffer_ostream` wants to do something different.  Could we afford to make `flush` virtual?  Not something needed for this patch.

I don't think making `flush()` virtual would help; `flush()` means "I want my changes to show up somewhere", but it does not mean "I'm done / EOF". `buffer_ostream` cannot forward to the buffered stream until it is sure that there will never be a(nother) `pwrite()` call. Otherwise it can't service the `pwrite()`.

But yeah, it's awkward.

What might be nice is if `createOutputFile()` took an argument saying "I don't need pwrite"; could implement that by not using `buffer_ostream`, and instead using a simple forwarding proxy that had `report_fatal_error` in `pwrite_impl()`.



================
Comment at: clang/lib/ExtractAPI/ExtractAPIConsumer.cpp:796
   SGSerializer.serialize(*OS);
-  OS->flush();
+  OS = nullptr;
 }
----------------
benlangmuir wrote:
> Nit: `OS.reset(nullptr);` makes it more obvious this is a `unique_ptr` and not a raw pointer. Same for the other cases as well.
I see your point; I'll update.


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https://reviews.llvm.org/D124635