span.cons/container.pass.cpp
N4842 22.7.3.2 [span.cons]/13 constrains span's range constructor
for ranges::contiguous_range (among other criteria).
24.4.5 [range.refinements]/2 says that contiguous_range requires data(),
and (via contiguous_range, random_access_range, bidirectional_range,
forward_range, input_range, range) it also requires begin() and end()
(see 24.4.2 [range.range]/1).
Therefore, IsAContainer needs to provide begin() and end().
(Detected by MSVC's concept-constrained implementation.)
span.cons/stdarray.pass.cpp
This test uses std::array, so it must include <array>.
<span> isn't guaranteed to drag in <array>.
(Detected by MSVC's implementation which uses a forward declaration to
avoid dragging in <array>, for increased compiler throughput.)
span.objectrep/as_bytes.pass.cpp
span.objectrep/as_writable_bytes.pass.cpp
Testing `sp.extent == std::dynamic_extent` triggers MSVC warning
C4127 "conditional expression is constant". Using `if constexpr` is a
simple way to avoid this without disrupting anyone else (as span
requires C++20 mode).
span.tuple/get.pass.cpp
22.7.3.2 [span.cons]/4.3: "Preconditions: If extent is not equal to
dynamic_extent, then count is equal to extent."
These lines were triggering undefined behavior (detected by assertions
in MSVC's implementation).
I changed the count arguments in the first two chunks, followed by
changing the span extents, in order to preserve the test's coverage
and follow the existing pattern.
span.cons/span.pass.cpp
22.7.3.2 [span.cons]/18.1 constrains span's converting constructor with
"Extent == dynamic_extent || Extent == OtherExtent is true".
This means that converting from dynamic extent to static extent is
not allowed. (Other constructors tested elsewhere, like
span(It first, size_type count), can be used to write such code.)
As this is the test for the converting constructor, I have:
* Removed the "dynamic -> static" case from checkCV(), which is
comprehensive.
* Changed the initialization of std::span<T, 0> s1{}; in
testConstexprSpan() and testRuntimeSpan(), because s1 is used below.
* Removed ASSERT_NOEXCEPT(std::span<T, 0>{s0}); from those functions,
as they are otherwise comprehensive.
* Deleted testConversionSpan() entirely. Note that this could never
compile (it had a bool return type, but forgot to say `return`). And it
couldn't have provided useful coverage, as the /18.2 constraint
"OtherElementType(*)[] is convertible to ElementType(*)[]"
permits only cv-qualifications, which are already tested by checkCV().
Summary:
Freestanding is *weird*. The standard allows it to differ in a bunch of odd
manners from regular C++, and the committee would like to improve that
situation. I'd like to make libc++ behave better with what freestanding should
be, so that it can be a tool we use in improving the standard. To do that we
need to try stuff out, both with "freestanding the language mode" and
"freestanding the library subset".
Let's start with the super basic: run the libc++ tests in freestanding, using
clang as the compiler, and see what works. The easiest hack to do this:
In utils/libcxx/test/config.py add:
self.cxx.compile_flags += ['-ffreestanding']
Run the tests and they all fail.
Why? Because in freestanding `main` isn't special. This "not special" property
has two effects: main doesn't get mangled, and main isn't allowed to omit its
`return` statement. The first means main gets mangled and the linker can't
create a valid executable for us to test. The second means we spew out warnings
(ew) and the compiler doesn't insert the `return` we omitted, and main just
falls of the end and does whatever undefined behavior (if you're luck, ud2
leading to non-zero return code).
Let's start my work with the basics. This patch changes all libc++ tests to
declare `main` as `int main(int, char**` so it mangles consistently (enabling us
to declare another `extern "C"` main for freestanding which calls the mangled
one), and adds `return 0;` to all places where it was missing. This touches 6124
files, and I apologize.
The former was done with The Magic Of Sed.
The later was done with a (not quite correct but decent) clang tool:
https://gist.github.com/jfbastien/793819ff360baa845483dde81170feed
This works for most tests, though I did have to adjust a few places when e.g.
the test runs with `-x c`, macros are used for main (such as for the filesystem
tests), etc.
Once this is in we can create a freestanding bot which will prevent further
regressions. After that, we can start the real work of supporting C++
freestanding fairly well in libc++.
<rdar://problem/47754795>
Reviewers: ldionne, mclow.lists, EricWF
Subscribers: christof, jkorous, dexonsmith, arphaman, miyuki, libcxx-commits
Differential Revision: https://reviews.llvm.org/D57624
llvm-svn: 353086
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
Stephan T. Lavavej