While working on D70631, Microsoft's unit tests discovered an issue.
Our `std::to_chars` implementation for bases != 10 uses the range
`[first,last)` as temporary buffer. This violates the contract for
to_chars:
[charconv.to.chars]/1 http://eel.is/c++draft/charconv#to.chars-1
`to_chars_result to_chars(char* first, char* last, see below value, int base = 10);`
"If the member ec of the return value is such that the value is equal to
the value of a value-initialized errc, the conversion was successful and
the member ptr is the one-past-the-end pointer of the characters
written."
Our implementation modifies the range `[member ptr, last)`, which causes
Microsoft's test to fail. Their test verifies the buffer
`[member ptr, last)` is unchanged. (The test is only done when the
conversion is successful.)
While looking at the code I noticed the performance for bases != 10 also
is suboptimal. This is tracked in D97705.
This patch fixes the issue and adds a benchmark. This benchmark will be
used as baseline for D97705.
Reviewed By: #libc, Quuxplusone, zoecarver
Differential Revision: https://reviews.llvm.org/D100722
[libcxx] [test] Calling min and max on an empty valarray is UB.
libcxx/test/std/numerics/numarray/template.valarray/valarray.members/min.pass.cpp
libcxx/test/std/numerics/numarray/template.valarray/valarray.members/max.pass.cpp
The calls `v1.min();` and `v1.max();` were emitting nodiscard warnings
with MSVC's STL. Upon closer inspection, these calls were triggering
undefined behavior. N4842 [valarray.members] says:
"T min() const;
8 Preconditions: size() > 0 is true.
T max() const;
10 Preconditions: size() > 0 is true."
As these tests already provide coverage for non-empty valarrays
(immediately above), I've simply deleted the code for empty valarrays.
[libcxx] [test] Add macros to msvc_stdlib_force_include.h (NFC).
libcxx/test/support/msvc_stdlib_force_include.h
These macros are being used by:
libcxx/test/std/utilities/meta/meta.trans/meta.trans.other/result_of11.pass.cpp
Defining them to nothing allows that test to pass.
[libcxx] [test] Silence MSVC warning C5063 for is_constant_evaluated (NFC).
libcxx/test/std/utilities/meta/meta.const.eval/is_constant_evaluated.pass.cpp
This test is intentionally writing code that MSVC intentionally warns
about, so the warning should be silenced.
Additionally, comment an endif for clarity.
[libcxx] [test] Silence MSVC warning C4127 (NFC).
libcxx/test/support/charconv_test_helpers.h
MSVC avoids emitting this warning when it sees a single constexpr value
being tested, but this condition is a mix of compile-time and run-time.
Using push-disable-pop is the least intrusive way to silence this.
[libcxx] [test] Silence MSVC truncation warning (NFC).
libcxx/test/std/containers/sequences/vector/vector.cons/construct_iter_iter.pass.cpp
This test is intentionally truncating float to int, which MSVC
intentionally warns about, so push-disable-pop is necessary.
[libcxx] [test] Avoid truncation warnings in erase_if tests (NFC).
libcxx/test/std/containers/associative/map/map.erasure/erase_if.pass.cpp
libcxx/test/std/containers/associative/multimap/multimap.erasure/erase_if.pass.cpp
libcxx/test/std/containers/unord/unord.map/erase_if.pass.cpp
libcxx/test/std/containers/unord/unord.multimap/erase_if.pass.cpp
These tests use maps with `short` keys and values, emitting MSVC
truncation warnings from `int`. Adding `static_cast` to `key_type`
and `mapped_type` avoids these warnings.
As these tests require C++20 mode (or newer), for brevity I've changed
the multimap tests to use emplace to initialize the test data.
This has no effect on the erase_if testing.
to reflect the new license. These used slightly different spellings that
defeated my regular expressions.
We understand that people may be surprised that we're moving the header
entirely to discuss the new license. We checked this carefully with the
Foundation's lawyer and we believe this is the correct approach.
Essentially, all code in the project is now made available by the LLVM
project under our new license, so you will see that the license headers
include that license only. Some of our contributors have contributed
code under our old license, and accordingly, we have retained a copy of
our old license notice in the top-level files in each project and
repository.
llvm-svn: 351648
Summary:
Major QoI considerations:
- The facility is backported to C++14, same as libstdc++.
- Efforts have been made to minimize the header dependencies.
- The design is friendly to the uses of MSVC intrinsics (`__emulu`, `_umul128`, `_BitScanForward`, `_BitScanForward64`) but not implemented; future contributions are welcome.
Thanks to Milo Yip for contributing the implementation of `__u64toa` and `__u32toa`.
References:
https://wg21.link/p0067r5https://wg21.link/p0682r1
Reviewers: mclow.lists, EricWF
Reviewed By: mclow.lists
Subscribers: ldionne, Quuxplusone, christof, mgorny, cfe-commits
Differential Revision: https://reviews.llvm.org/D41458
llvm-svn: 338479
Mark de Wever