[PATCH] D49240: [libc++] Introduce _LIBCPP_HIDE_FROM_ABI to replace _LIBCPP_INLINE_VISIBILITY

[Louis Dionne via Phabricator via cfe-commits]

ldionne added a comment.

In https://reviews.llvm.org/D49240#1195723, @rnk wrote:

> In https://reviews.llvm.org/D49240#1195237, @ldionne wrote:
>
> > In https://reviews.llvm.org/D49240#1195125, @thakis wrote:
> >
> > > When we updated out clang bundle in chromium (which includes libc++ headers), our ios simulator bots regressed debug info size by ~50% due to this commit (https://bugs.chromium.org/p/chromium/issues/detail?id=872926#c13). Is that expected?
> >
> >
> > No, this is quite surprising. What happened with the size of the Release builds? We should investigate, perhaps this change exposed something in Clang's debug info generation.
>
>
> It looks like the increase is entirely from more symbols in the symbol table. It's not a problem with clang's debug info. It would help a lot if ld64 de-duplicated strings in the symbol table, if that's possible.
>
> [...]


Ah, thanks a lot for taking a look! Yes, this makes a lot of sense, since now we're not inlining everything anymore. So the code size is actually smaller (-9.8%), but there's more symbols because more functions are emitted. In this case, I would say this is expected, if unfortunate. Also, a similar effect would probably be witnessed if Chromium were to change their standard library to libstdc++, for example, since libstdc++ does not abuse inlining like libc++ used to.


Repository:
  rCXX libc++

https://reviews.llvm.org/D49240