Commit Graph

3 Commits

Author SHA1 Message Date
Roman Lebedev
8ee872ed9e [libcxx] Readjust nodiscard_extensions.pass.cpp test - just disable for ASAN
In rL342814, i have committed a blind fix to unbreak the asan buildbot,
but as it was later discussed, the leak is intentional,
so we can not fix the failure that way.

So this reverts the leak 'fix',
and simply disables the test in the presence of ASAN.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@342819 91177308-0d34-0410-b5e6-96231b3b80d8
2018-09-22 20:07:02 +00:00
Roman Lebedev
4a5c6f3482 [libcxx] Blind attempt to fix harmless leak in nodiscard_extensions.pass.cpp test
libcxx-libcxxabi-x86_64-linux-ubuntu-asan complains about a leak here.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@342814 91177308-0d34-0410-b5e6-96231b3b80d8
2018-09-22 19:09:57 +00:00
Roman Lebedev
caf40ae419 [libc++] Add _LIBCPP_ENABLE_NODISCARD and _LIBCPP_NODISCARD_EXT to allow pre-C++2a [[nodiscard]]
Summary:
The `[[nodiscard]]` attribute is intended to help users find bugs where
function return values are ignored when they shouldn't be. After C++17 the
C++ standard has started to declared such library functions as `[[nodiscard]]`.
However, this application is limited and applies only to dialects after C++17.
Users who want help diagnosing misuses of STL functions may desire a more
liberal application of `[[nodiscard]]`.

For this reason libc++ provides an extension that does just that! The
extension must be enabled by defining `_LIBCPP_ENABLE_NODISCARD`. The extended
applications of `[[nodiscard]]` takes two forms:

1. Backporting `[[nodiscard]]` to entities declared as such by the
   standard in newer dialects, but not in the present one.

2. Extended applications of `[[nodiscard]]`, at the libraries discretion,
   applied to entities never declared as such by the standard.

Users may also opt-out of additional applications `[[nodiscard]]` using
additional macros.

Applications of the first form, which backport `[[nodiscard]]` from a newer
dialect may be disabled using macros specific to the dialect it was added. For
example `_LIBCPP_DISABLE_NODISCARD_AFTER_CXX17`.

Applications of the second form, which are pure extensions, may be disabled
by defining `_LIBCPP_DISABLE_NODISCARD_EXT`.

This patch was originally written by me (Roman Lebedev),
then but then reworked by Eric Fiselier.

Reviewers: mclow.lists, thakis, EricWF

Reviewed By: thakis, EricWF

Subscribers: llvm-commits, mclow.lists, lebedev.ri, EricWF, rjmccall, Quuxplusone, cfe-commits, christof

Differential Revision: https://reviews.llvm.org/D45179

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@342808 91177308-0d34-0410-b5e6-96231b3b80d8
2018-09-22 17:54:48 +00:00