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AK+Everywhere: Do not implicitly copy variables in TRY macros

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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.
This commit is contained in:
Timothy Flynn 2023-02-09 13:27:43 -05:00 committed by Linus Groh
parent 4a916cd379
commit 604d5f5bca
Notes: sideshowbarker 2024-07-18 05:01:22 +09:00 
Author: https://github.com/trflynn89
Commit: https://github.com/SerenityOS/serenity/commit/604d5f5bca
Pull-request: https://github.com/SerenityOS/serenity/pull/17399
Reviewed-by: https://github.com/linusg
11 changed files with 15 additions and 15 deletions
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4
AK/Try.h
View file

@ -25,7 +25,7 @@
({ \
/* Ignore -Wshadow to allow nesting the macro. */ \
AK_IGNORE_DIAGNOSTIC("-Wshadow", \
auto _temporary_result = (expression)); \
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]] \
@ -37,7 +37,7 @@
({ \
/* Ignore -Wshadow to allow nesting the macro. */ \
AK_IGNORE_DIAGNOSTIC("-Wshadow", \
auto _temporary_result = (expression)); \
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()); \

2
Kernel/Net/Socket.h
View file

@ -188,7 +188,7 @@ private:
// This is a special variant of TRY() that also updates the socket's SO_ERROR field on error.
#define SOCKET_TRY(expression) \
({ \
auto result = (expression); \
auto&& result = (expression); \
if (result.is_error()) \
return set_so_error(result.release_error()); \
static_assert(!::AK::Detail::IsLvalueReference<decltype(result.release_value())>, \

2
Meta/Lagom/Tools/CodeGenerators/LibLocale/GenerateLocaleData.cpp
View file

@ -233,7 +233,7 @@ struct CLDR {
// with locales such as "en-GB-oed" that are canonically invalid locale IDs.
#define TRY_OR_DISCARD(expression) \
({ \
auto _temporary_result = (expression); \
auto&& _temporary_result = (expression); \
if (_temporary_result.is_error()) \
return; \
static_assert(!::AK::Detail::IsLvalueReference<decltype(_temporary_result.release_value())>, \

2
Userland/Libraries/LibAudio/LoaderError.h
View file

@ -68,7 +68,7 @@ struct LoaderError {
// Convenience TRY-like macro to convert an Error to a LoaderError
#define LOADER_TRY(expression) \
({ \
auto _temporary_result = (expression); \
auto&& _temporary_result = (expression); \
if (_temporary_result.is_error()) \
return LoaderError(_temporary_result.release_error()); \
static_assert(!::AK::Detail::IsLvalueReference<decltype(_temporary_result.release_value())>, \

4
Userland/Libraries/LibJS/Runtime/Completion.h
View file

@ -21,7 +21,7 @@ namespace JS {
({ \
/* Ignore -Wshadow to allow nesting the macro. */ \
AK_IGNORE_DIAGNOSTIC("-Wshadow", \
auto _temporary_result = (expression)); \
auto&& _temporary_result = (expression)); \
if (_temporary_result.is_error()) { \
VERIFY(_temporary_result.error().code() == ENOMEM); \
return vm.throw_completion<JS::InternalError>(JS::ErrorType::OutOfMemory); \
@ -35,7 +35,7 @@ namespace JS {
({ \
/* Ignore -Wshadow to allow nesting the macro. */ \
AK_IGNORE_DIAGNOSTIC("-Wshadow", \
auto _temporary_result = (expression)); \
auto&& _temporary_result = (expression)); \
if (_temporary_result.is_error()) { \
auto _completion = _temporary_result.release_error(); \
\

4
Userland/Libraries/LibJS/Runtime/PromiseCapability.h
View file

@ -43,7 +43,7 @@ private:
// 27.2.1.1.1 IfAbruptRejectPromise ( value, capability ), https://tc39.es/ecma262/#sec-ifabruptrejectpromise
#define __TRY_OR_REJECT(vm, capability, expression, CALL_CHECK) \
({ \
auto _temporary_try_or_reject_result = (expression); \
auto&& _temporary_try_or_reject_result = (expression); \
/* 1. If value is an abrupt completion, then */ \
if (_temporary_try_or_reject_result.is_error()) { \
/* a. Perform ? Call(capability.[[Reject]], undefined, « value.[[Value]] »). */ \
@ -69,7 +69,7 @@ private:
// 27.2.1.1.1 IfAbruptRejectPromise ( value, capability ), https://tc39.es/ecma262/#sec-ifabruptrejectpromise
#define TRY_OR_REJECT_WITH_VALUE(vm, capability, expression) \
({ \
auto _temporary_try_or_reject_result = (expression); \
auto&& _temporary_try_or_reject_result = (expression); \
/* 1. If value is an abrupt completion, then */ \
if (_temporary_try_or_reject_result.is_error()) { \
/* a. Perform ? Call(capability.[[Reject]], undefined, « value.[[Value]] »). */ \

2
Userland/Libraries/LibVideo/DecoderError.h
View file

@ -79,7 +79,7 @@ private:
#define DECODER_TRY(category, expression) \
({ \
auto _result = ((expression)); \
auto&& _result = ((expression)); \
if (_result.is_error()) [[unlikely]] { \
auto _error_string = _result.release_error().string_literal(); \
return DecoderError::from_source_location( \

4
Userland/Libraries/LibVideo/PlaybackManager.cpp
View file

@ -15,7 +15,7 @@ namespace Video {
#define TRY_OR_FATAL_ERROR(expression) \
({ \
auto _fatal_expression = (expression); \
auto&& _fatal_expression = (expression); \
if (_fatal_expression.is_error()) { \
dispatch_fatal_error(_fatal_expression.release_error()); \
return; \
@ -156,7 +156,7 @@ bool PlaybackManager::decode_and_queue_one_sample()
#define TRY_OR_ENQUEUE_ERROR(expression) \
({ \
auto _temporary_result = ((expression)); \
auto&& _temporary_result = ((expression)); \
if (_temporary_result.is_error()) { \
dbgln_if(PLAYBACK_MANAGER_DEBUG, "Enqueued decoder error: {}", _temporary_result.error().string_literal()); \
m_frame_queue->enqueue(FrameQueueItem::error_marker(_temporary_result.release_error())); \

2
Userland/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
View file

@ -44,7 +44,7 @@ namespace Web::Fetch::Fetching {
#define TRY_OR_IGNORE(expression) \
({ \
auto _temporary_result = (expression); \
auto&& _temporary_result = (expression); \
if (_temporary_result.is_error()) \
return; \
static_assert(!::AK::Detail::IsLvalueReference<decltype(_temporary_result.release_value())>, \

2
Userland/Libraries/LibWeb/WebDriver/ExecuteScript.cpp
View file

@ -33,7 +33,7 @@ namespace Web::WebDriver {
#define TRY_OR_JS_ERROR(expression) \
({ \
auto _temporary_result = (expression); \
auto&& _temporary_result = (expression); \
if (_temporary_result.is_error()) [[unlikely]] \
return ExecuteScriptResultType::JavaScriptError; \
static_assert(!::AK::Detail::IsLvalueReference<decltype(_temporary_result.release_value())>, \

2
Userland/Utilities/matroska.cpp
View file

@ -12,7 +12,7 @@
#define TRY_PARSE(expression) \
({ \
auto _temporary_result = ((expression)); \
auto&& _temporary_result = ((expression)); \
if (_temporary_result.is_error()) [[unlikely]] { \
outln("Encountered a parsing error: {}", _temporary_result.error().string_literal()); \
return Error::from_string_literal("Failed to parse :("); \