That pattern seems to show up a lot in code written by people that
aren't intimately familiar with the lifetime model of Error and Strings.
This commit makes the compiler detect it and present a more helpful
diagnostic than "garbage string at runtime".
It wouldn't make much sense on its own (as the Kernel only has errno
Errors), but it's an easy fix for not having to ifdef away every single
usage of `is_errno` in code that is shared between Userland and Kernel.
This code should not be used in the kernel - we should always propagate
proper errno codes in case we need to return those to userland so it
could decode it in a reasonable way.
This new method is meant to be used in both userspace and kernel code.
The idea is to allow printing of a verbose message and then returning an
errno code which is the proper mechanism for kernel code because we
should almost always assume that such error will be propagated back to
userspace in some way, so the userspace code could reasonably decode it.
For userspace code however, this new method is meant to be a simple
wrapper for Error::from_string_view, because for most invocations, it's
much more useful to have a verbose & literal error than a errno code, so
we simply ignore that errno code completely in such context.
As of now, there is a default copy constructor on Error. A future commit
will make this non-public to prevent implicit copies, so to prepare for
that, this adds a factory for the few cases where a copy is really
needed.
Mark other ErrorOr types as friends, and fix a typo in the &&
constructor, so that we can create an ErrorOr<Core::Object> from an
ErrorOr<GUI::Widget>. Also, add some requires() clauses to these
constructors so the error messages are clearer.
This shrinks sizeof(Error) from 32 bytes to 24 bytes, which in turn will
shrink sizeof(ErrorOr<T>) by the same amount (in cases where sizeof(T)
is less than sizeof(Error)).
Note that Jakt only allows StringView creation from string literals, so
none of the invariants in the class are broken by this (if used only
from within Jakt).
This patch adds the `USING_AK_GLOBALLY` macro which is enabled by
default, but can be overridden by build flags.
This is a step towards integrating Jakt and AK types.
GCC seems to get tripped up over this inheritance when converting from
an ErrorOr<StringView> to the partially specialized ErrorOr<void>. See
the following snippet:
NEVER_INLINE ErrorOr<StringView> foo()
{
auto string = "abc"sv;
outln("{:p}", string.characters_without_null_termination());
return string;
}
NEVER_INLINE ErrorOr<void> bar()
{
auto string = TRY(foo());
outln("{:p}", string.characters_without_null_termination());
VERIFY(!string.starts_with('#'));
return {};
}
int main()
{
MUST(bar());
}
On some machines, bar() will contain a StringView whose pointer has had
its upper bits set to 0:
0x000000010cafd6f8
0x000000000cafd6f8
I'm not 100% clear on what's happening in the default-generated Variant
destructor that causes this. Probably worth investigating further.
The error would also be alleviated by making the Variant destructor
virtual, but rather than that, let's make ErrorOr simply contain a
Variant rather than inherit from it.
Fixes#15449.
Error::from_string_literal now takes direct char const*s, while
Error::from_string_view does what Error::from_string_literal used to do:
taking StringViews. This change will remove the need to insert `sv`
after error strings when returning string literal errors once
StringView(char const*) is removed.
No functional changes.
While the code did already VERIFY that the ErrorOr holds a value, this
was done by Variant, so the error message was just that `has<T>()` is
false. This is less helpful than I would like, especially if backtraces
are not working and this is all you have to go on. Adding this extra
VERIFY means the assertion message (`!is_error()`) is easier to
understand.
This fixes at least half of our LibC includes in the kernel. The source
of truth for errno codes and their description strings now lives in
Kernel/API/POSIX/errno.h as an enumeration, which LibC includes.
Note that the return type for the non-const method error() changed. This
is most likely an accident, hidden by the fact that ErrorType typically
is Error.
This creates an error that contains the name of the syscall that failed.
This allows error handlers to print out the name of the call if they
want to. :^)
This isn't a complete conversion to ErrorOr<void>, but a good chunk.
The end goal here is to propagate buffer allocation failures to the
caller, and allow the use of TRY() with formatting functions.
This is an alternative to ErrorOr<T>::release_value() that can be used
when converting code to signal that we're releasing the value without
error propagation as a way to move forward now.
This makes these cases much easier to find later on, once more paths for
error propagation are available.
The goal with these is to eventually replace AK::Result, KResult and
KResultOr<T> with something that works (and makes sense) in both kernel
and userspace.
This first cut of Error can be made from an errno code, or from a string
literal (StringView)
As suggested by Joshua, this commit adds the 2-clause BSD license as a
comment block to the top of every source file.
For the first pass, I've just added myself for simplicity. I encourage
everyone to add themselves as copyright holders of any file they've
added or modified in some significant way. If I've added myself in
error somewhere, feel free to replace it with the appropriate copyright
holder instead.
Going forward, all new source files should include a license header.
Put simply, Error<> is a way of forcing error handling onto an API user.
Given a function like:
bool might_work();
The following code might have been written previously:
might_work(); // but what if it didn't?
The easy way to work around this is of course to [[nodiscard]] might_work.
But this doesn't work for more complex cases like, for instance, a
hypothetical read() function which might return one of _many_ errors
(typically signalled with an int, let's say).
int might_read();
In such a case, the result is often _read_, but not properly handled. Like:
return buffer.substr(0, might_read()); // but what if might_read returned an error?
This is where Error<> comes in:
typedef Error<int, 0> ReadError;
ReadError might_read();
auto res = might_read();
if (might_read.failed()) {
switch (res.value()) {
case EBADF:
...
}
}
Error<> uses clang's consumable attributes to force failed() to be
checked on an Error instance. If it's not checked, then you get smacked.
