[libc++] Use exclude_from_explicit_instantiation instead of always_inline
Summary:
This commit adopts the exclude_from_explicit_instantiation attribute discussed
at [1] and reviewed in [2] in libc++ to supplant the use of __always_inline__
for visibility purposes.
This change means that users wanting to link together translation units built
with different versions of libc++'s headers into the same final linked image
MUST define the _LIBCPP_HIDE_FROM_ABI_PER_TU macro to 1 when building those
TUs. Doing otherwise will lead to ODR violations and ABI issues.
[1]: http://lists.llvm.org/pipermail/cfe-dev/2018-August/059024.html
[2]: https://reviews.llvm.org/D51789
Reviewers: rsmith, EricWF
Subscribers: dexonsmith, libcxx-commits
Differential Revision: https://reviews.llvm.org/D52405
llvm-svn: 345516
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: e9d85264ac4cdf505c7497612d3fe7630590c52f
diff --git a/docs/ReleaseNotes.rst b/docs/ReleaseNotes.rst
index 52d7a1e..4cf5182 100644
--- a/docs/ReleaseNotes.rst
+++ b/docs/ReleaseNotes.rst
@@ -41,3 +41,10 @@
API Changes
-----------
- Building libc++ for Mac OSX 10.6 is not supported anymore.
+- Starting with LLVM 8.0.0, users that wish to link together translation units
+ built with different versions of libc++'s headers into the same final linked
+ image MUST define the _LIBCPP_HIDE_FROM_ABI_PER_TU macro to 1 when building
+ those translation units. Not defining _LIBCPP_HIDE_FROM_ABI_PER_TU to 1 and
+ linking translation units built with different versions of libc++'s headers
+ together may lead to ODR violations and ABI issues. On the flipside, code
+ size improvements should be expected for everyone not defining the macro.