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AK+Everywhere: Disallow returning a reference from a fallible expression

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This will silently make a copy. Rather than masking this behavior, let's
explicitly disallow it.
This commit is contained in:
Timothy Flynn 2023-01-13 15:48:09 -05:00 • committed by Tim Flynn
parent 3de75f6436
commit afc0e461e1
11 changed files with 86 additions and 54 deletions
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38
AK/Try.h
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@ -15,22 +15,30 @@
// 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)); \
if (_temporary_result.is_error()) [[unlikely]] \
return _temporary_result.release_error(); \
_temporary_result.release_value(); \
#define TRY(expression) \
({ \
/* Ignore -Wshadow to allow nesting the macro. */ \
AK_IGNORE_DIAGNOSTIC("-Wshadow", \
auto _temporary_result = (expression)); \
static_assert(!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)); \
VERIFY(!_temporary_result.is_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(!IsLvalueReference<decltype(_temporary_result.release_value())>, \
"Do not return a reference from a fallible expression"); \
VERIFY(!_temporary_result.is_error()); \
_temporary_result.release_value(); \
})