This reverts commit 1c92d4c5db and
reintroduces support for trivially copyable `maybe_t` impls but with a
GCC version check to disable the optimization for GNU GCC compiler
versions 9 and below.
GCC 8.3.0 armhf builds seem to have a problem with the trivially
copyable `maybe_t` impl that introduces odd heisenbugs that cause the
tests to fail. GDB reveals that `maybe_t` function parameters received
in the callee differ from what was passed-in by the caller.
This behavior appears to be (but has not been confirmed as) a
platform-specific compiler bug. Under the same system (32-bit Debian 10
armhf), compiling with clang 7.0.1 does not result in any bugs and
causes all the tests to pass while compiling with GCC 10.2 under 32-bit
Debian 11 armhf also doesn't run into any problems, so just expand the
existing GCC version check that gates support for trivially copyable
`maybe_t` impls to encompass both the troublesome GCC 8 version and the
untested GCC 9 version.
This reverts commit 9d303a74e3.
This reverts commit 0305c842e6.
9d303a7 broke 32-bit armhf builds for unknown reasons, specifically in
settings where a trivial copy of `maybe_t<int>` was performed. A caller
would pass a literal int in the place of a `maybe_t<int>` parameter and
the callee would see a populated `maybe_t` but with a value of `0`
rather than the actual value that was passed in. It was too painful to
debug to a resolution under qemu.
When passing a value of type maybe_t<size_t>, clangd complains:
Parameter 'cursor' is passed by value and only copied once; consider
moving it to avoid unnecessary copies (fix available)
We get this warning because maybe_t<size_t> is not trivially copyable
because it has a user-defined destructor and copy-constructor. Let's remove
them if the contained type is trivially copyable, to avoid such warnings.
No functional change.
The destructor is equivalent to the compiler-generated one. The user-defined
destructor prevents maybe_t<size_t> from bearing the predicate "trivially
copyable". Let's remove it. No functional change.
Closes#9240.
Squash of the following commits (in reverse-chronological order):
commit 03b5cab3dc40eca9d50a9df07a8a32524338a807
Author: Mahmoud Al-Qudsi <mqudsi@neosmart.net>
Date: Sun Sep 25 15:09:04 2022 -0500
Handle differently declared posix_spawnxxx_t on macOS
On macOS, posix_spawnattr_t and posix_spawn_file_actions_t are declared as void
pointers, so we can't use maybe_t's bool operator to test if it has a value.
commit aed83b8bb308120c0f287814d108b5914593630a
Author: Mahmoud Al-Qudsi <mqudsi@neosmart.net>
Date: Sun Sep 25 14:48:46 2022 -0500
Update maybe_t tests to reflect dynamic bool conversion
maybe_t<T> is now bool-convertible only if T _isn't_ already bool-convertible.
commit 2b5a12ca97b46f96b1c6b56a41aafcbdb0dfddd6
Author: Mahmoud Al-Qudsi <mqudsi@neosmart.net>
Date: Sun Sep 25 14:34:03 2022 -0500
Make maybe_t a little harder to misuse
We've had a few bugs over the years stemming from accidental misuse of maybe_t
with bool-convertible types. This patch disables maybe_t's bool operator if the
type T is already bool convertible, forcing the (barely worth mentioning) need
to use maybe_t::has_value() instead.
This patch both removes maybe_t's bool conversion for bool-convertible types and
updates the existing codebase to use the explicit `has_value()` method in place
of existing implicit bool conversions.
This is required for the usage of placement new. Not an issue for fish
as it gets picked up from elsewhere, but it lets one use it in a C++
test directly this way.
This runs build_tools/style.fish, which runs clang-format on C++, fish_indent on fish and (new) black on python.
If anything is wrong with the formatting, we should fix the tools, but automated formatting is worth it.
maybe_t is an implementation of the Maybe/Optional type, allowing
for an optional value to be stored. This will enable a more
principled approach for functions that return values or failure,
such as env_get.
