mirror of
https://github.com/LadybirdBrowser/ladybird.git
synced 2024-11-29 19:10:26 +00:00
604d5f5bca
For example, consider cases where we want to propagate errors only in
specific instances:
auto result = read_data(); // something like ErrorOr<ByteBuffer>
if (result.is_error() && result.error().code() != EINTR)
continue;
auto bytes = TRY(result);
The TRY invocation will currently copy the byte buffer when the
expression (in this case, just a local variable) is stored into
_temporary_result.
This patch binds the expression to a reference to prevent such copies.
In less trival invocations (such as TRY(some_function()), this will
incur only temporary lifetime extensions, i.e. no functional change.
45 lines
2.7 KiB
C
45 lines
2.7 KiB
C
/*
|
|
* Copyright (c) 2021, Andreas Kling <kling@serenityos.org>
|
|
*
|
|
* SPDX-License-Identifier: BSD-2-Clause
|
|
*/
|
|
|
|
#pragma once
|
|
|
|
#include <AK/Diagnostics.h>
|
|
#include <AK/StdLibExtras.h>
|
|
|
|
// NOTE: This macro works with any result type that has the expected APIs.
|
|
// It's designed with AK::Result and AK::Error in mind.
|
|
//
|
|
// It depends on a non-standard C++ extension, specifically
|
|
// on statement expressions [1]. This is known to be implemented
|
|
// by at least clang and gcc.
|
|
// [1] https://gcc.gnu.org/onlinedocs/gcc/Statement-Exprs.html
|
|
//
|
|
// If the static_assert below is triggered, it means you tried to return a reference
|
|
// from a fallible expression. This will not do what you want; the statement expression
|
|
// will create a copy regardless, so it is explicitly disallowed.
|
|
|
|
#define TRY(expression) \
|
|
({ \
|
|
/* Ignore -Wshadow to allow nesting the macro. */ \
|
|
AK_IGNORE_DIAGNOSTIC("-Wshadow", \
|
|
auto&& _temporary_result = (expression)); \
|
|
static_assert(!::AK::Detail::IsLvalueReference<decltype(_temporary_result.release_value())>, \
|
|
"Do not return a reference from a fallible expression"); \
|
|
if (_temporary_result.is_error()) [[unlikely]] \
|
|
return _temporary_result.release_error(); \
|
|
_temporary_result.release_value(); \
|
|
})
|
|
|
|
#define MUST(expression) \
|
|
({ \
|
|
/* Ignore -Wshadow to allow nesting the macro. */ \
|
|
AK_IGNORE_DIAGNOSTIC("-Wshadow", \
|
|
auto&& _temporary_result = (expression)); \
|
|
static_assert(!::AK::Detail::IsLvalueReference<decltype(_temporary_result.release_value())>, \
|
|
"Do not return a reference from a fallible expression"); \
|
|
VERIFY(!_temporary_result.is_error()); \
|
|
_temporary_result.release_value(); \
|
|
})
|