llvm/libcxx
1
0
Fork 0
mirror of https://github.com/llvm-mirror/libcxx.git synced 2025-10-23 10:07:41 +08:00
Code Issues Packages Projects Releases Wiki Activity

[libc++] Support Microsoft ABI without vcruntime headers

Browse Source 
The vcruntime headers are hairy and clash with both libc++ headers
themselves and other libraries. libc++ normally deals with the clashes
by deferring to the vcruntime headers and silencing its own definitions,
but for clients which don't want to depend on vcruntime headers, it's
desirable to support the opposite, i.e. have libc++ provide its own
definitions.

Certain operator new/delete replacement scenarios are not currently
supported in this mode, which requires some tests to be marked XFAIL.
The added documentation has more details.

Differential Revision: https://reviews.llvm.org/D38522

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@315234 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Shoaib Meenai
2017-10-09 19:25:17 +00:00
parent 7762784b98
commit 18dba06924
12 changed files with 137 additions and 27 deletions
Download Patch File Download Diff File Expand all files Collapse all files

20
docs/UsingLibcxx.rst
View File

@@ -185,6 +185,26 @@ thread safety annotations.
* Giving `set`, `map`, `multiset`, `multimap` a comparator which is not
const callable.
**_LIBCPP_NO_VCRUNTIME**:
Microsoft's C and C++ headers are fairly entangled, and some of their C++
headers are fairly hard to avoid. In particular, `vcruntime_new.h` gets pulled
in from a lot of other headers and provides definitions which clash with
libc++ headers, such as `nothrow_t` (note that `nothrow_t` is a struct, so
there's no way for libc++ to provide a compatible definition, since you can't
have multiple definitions).
By default, libc++ solves this problem by deferring to Microsoft's vcruntime
headers where needed. However, it may be undesirable to depend on vcruntime
headers, since they may not always be available in cross-compilation setups,
or they may clash with other headers. The `_LIBCPP_NO_VCRUNTIME` macro
prevents libc++ from depending on vcruntime headers. Consequently, it also
prevents libc++ headers from being interoperable with vcruntime headers (from
the aforementioned clashes), so users of this macro are promising to not
attempt to combine libc++ headers with the problematic vcruntime headers. This
macro also currently prevents certain `operator new`/`operator delete`
replacement scenarios from working, e.g. replacing `operator new` and
expecting a non-replaced `operator new[]` to call the replaced `operator new`.
C++17 Specific Configuration Macros
-----------------------------------
**_LIBCPP_ENABLE_CXX17_REMOVED_FEATURES**: