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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
11 changed files with 15 additions and 15 deletions
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4
Userland/Libraries/LibJS/Runtime/PromiseCapability.h
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@ -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]] »). */ \