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Attributes hi(attribute) are compiler directives that are inserted into source
files to inform the compiler of some peculiarity of the code (variable or
function) following the attribute.
The C++ standard defines the following attributes:
itemization(
ithtq(noreturn)([[noreturn]])
(tt([[noreturn]]) indicates that the function does not
return. tt([[noreturn]]'s) behavior is undefined if the function declared with
this attribute actually returns. The following standard functions have this
attribute: tt(std::_Exit, std::abort, std::exit, std::quick_exit,
std::unexpected, std::terminate, std::rethrow_exception,
std::throw_with_nested, std::nested_exception::rethrow_nested), Here is an
example of a function declaration and definition using the tt([[noreturn]])
attribute:
verb(
[[noreturn]] void doesntReturn();
[[noreturn]] void doesntReturn()
{
exit(0);
}
)
)
ithtq(carries_dependency)([[carries_dependency]])
(This attribute is currently not yet covered by the annotations(). At
this point in the annotations() it can safely be ignored.
COMMENT(
tt([[carries_dependency]]) Indicates that dependency chain in
release-consume std::memory_order propagates in and out of the function, which
allows the compiler to skip unnecessary memory fence instructions. This
attribute may appear in two situations:
(1) it may apply to the parameter declarations of a function or
lambda-expressions, in which case it indicates that initialization of the
parameter carries dependency into lvalue-to-rvalue conversion of that object.
(2) It may apply to the function declaration as a whole, in which case it
indicates that the return value carries dependency to the evaluation of the
function call expression.
This attribute must appear on the first declaration of a function or one of
its parameters in any translation unit. If it is not used on the first
declaration of a function or one of its parameters in another translation
unit, the program is ill-formed; no diagnostic required.
See std::kill_dependency for example usage
END)
)
ithtq(deprecated)([[deprecated]])
(This attribute (and its alternative form
tt([[deprecated("reason")]])) is available since the C++14 standard. It
indicates that the use of the name or entity declared with this attribute is
allowed, but discouraged for some reason. This attribute can be used for
classes, typedef-names, variables, non-static data members, functions,
enumerations, and template specializations. An existing non-deprecated entity
may be redeclared deprecated, but once an entity has been declared deprecated
it cannot be redeclared as `undeprecated'. When encountering the
tt([[deprecated]]) attribute the compiler generates a warning, e.g.,
verb(
demo.cc:12:24: warning: 'void deprecatedFunction()' is deprecated
[-Wdeprecated-declarations] deprecatedFunction();
demo.cc:5:21: note: declared here
[[deprecated]] void deprecatedFunction()
)
When using the alternative form (e.g.,
tt([[deprecated("do not use")]] void fun())) the compiler generates a
warning showing the text between the double quotes, e.g.,
verb(
demo.cc:12:24: warning: 'void deprecatedFunction()' is deprecated:
do not use [-Wdeprecated-declarations]
deprecatedFunction();
demo.cc:5:38: note: declared here
[[deprecated("do not use")]] void deprecatedFunction()
)
)
)
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