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Diffstat (limited to 'gcc/doc/extend.texi')
-rw-r--r-- | gcc/doc/extend.texi | 119 |
1 files changed, 119 insertions, 0 deletions
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi index d01e5fa..ccdc995 100644 --- a/gcc/doc/extend.texi +++ b/gcc/doc/extend.texi @@ -10675,6 +10675,7 @@ Predefined Macros,cpp,The GNU C Preprocessor}). method denoted by a @samp{->*} or @samp{.*} expression. * C++ Attributes:: Variable, function, and type attributes for C++ only. * Namespace Association:: Strong using-directives for namespace association. +* Type Traits:: Compiler support for type traits * Java Exceptions:: Tweaking exception handling to work with Java. * Deprecated Features:: Things will disappear from g++. * Backwards Compatibility:: Compatibilities with earlier definitions of C++. @@ -11232,6 +11233,124 @@ int main() @} @end smallexample +@node Type Traits +@section Type Traits + +The C++ front-end implements syntactic extensions that allow to +determine at compile time various characteristics of a type (or of a +pair of types). + +@table @code +@item __has_nothrow_assign (type) +If @code{__has_trivial_assign (type)} is true then the trait is true, else if +@code{type} is a cv class or union type with copy assignment operators that +are known not to throw an exception then the trait is true, else it is false. +If @code{type} is const qualified, any copy assignment operator must +be both known not to throw an exception, and const qualified, for the +trait to be true. Requires: @code{type} shall be a complete type, an +array type of unknown bound, or is a @code{void} type. + +@item __has_nothrow_copy (type) +If @code{__has_trivial_copy (type)} is true then the trait is true, else if +@code{type} is a cv class or union type with copy constructors that +are known not to throw an exception then the trait is true, else it is false. +Requires: @code{type} shall be a complete type, an array type of +unknown bound, or is a @code{void} type. + +@item __has_nothrow_constructor (type) +If @code{__has_trivial_constructor (type)} is true then the trait is +true, else if @code{type} is a cv class or union type (or array +thereof) with a default constructor that is known not to throw an +exception then the trait is true, else it is false. Requires: +@code{type} shall be a complete type, an array type of unknown bound, +or is a @code{void} type. + +@item __has_trivial_assign (type) +If @code{type} is const qualified or is a reference type then the trait is +false. Otherwise if @code{__is_pod (type)} is true then the trait is +true, else if @code{type} is a cv class or union type with a trivial +copy assignment ([class.copy]) then the trait is true, else it is +false. Requires: @code{type} shall be a complete type, an array type +of unknown bound, or is a @code{void} type. + +@item __has_trivial_copy (type) +If @code{__is_pod (type)} is true or @code{type} is a reference type +then the trait is true, else if @code{type} is a cv class or union type +with a trivial copy constructor ([class.copy]) then the trait +is true, else it is false. Requires: @code{type} shall be a complete +type, an array type of unknown bound, or is a @code{void} type. + +@item __has_trivial_constructor (type) +If @code{__is_pod (type)} is true then the trait is true, else if +@code{type} is a cv class or union type (or array thereof) with a +trivial default constructor ([class.ctor]) then the trait is true, +else it is false. Requires: @code{type} shall be a complete type, an +array type of unknown bound, or is a @code{void} type. + +@item __has_trivial_destructor (type) +If @code{__is_pod (type)} is true or @code{type} is a reference type then +the trait is true, else if @code{type} is a cv class or union type (or +array thereof) with a trivial destructor ([class.dtor]) then the trait +is true, else it is false. Requires: @code{type} shall be a complete +type, an array type of unknown bound, or is a @code{void} type. + +@item __has_virtual_destructor (type) +If @code{type} is a class type with a virtual destructor +([class.dtor]) then the trait is true, else it is false. Requires: +@code{type} shall be a complete type, an array type of unknown bound, +or is a @code{void} type. + +@item __is_abstract (type) +If @code{type} is an abstract class ([class.abstract]) then the trait +is true, else it is false. Requires: @code{type} shall be a complete +type, an array type of unknown bound, or is a @code{void} type. + +@item __is_base_of (base_type, derived_type) +If @code{base_type} is a base class of @code{derived_type} +([class.derived]) then the trait is true, otherwise it is false. +Top-level cv qualifications of @code{base_type} and +@code{derived_type} are ignored. For the purposes of this trait, a +class type is considered is own base. Requires: if @code{__is_class +(base_type)} and @code{__is_class (derived_type)} are true and +@code{base_type} and @code{derived_type} are not the same type +(disregarding cv-qualifiers), @code{derived_type} shall be a complete +type. Diagnostic is produced if this requirement is not met. + +@item __is_class (type) +If @code{type} is a cv class type, and not a union type +([basic.compound]) the the trait is true, else it is false. + +@item __is_empty (type) +If @code{__is_class (type)} is false then the trait is false. +Otherwise @code{type} is considered empty if and only if: @code{type} +has no non-static data members, or all non-static data members, if +any, are bit-fields of lenght 0, and @code{type} has no virtual +members, and @code{type} has no virtual base classes, and @code{type} +has no base classes @code{base_type} for which +@code{__is_empty (base_type)} is false. Requires: @code{type} shall +be a complete type, an array type of unknown bound, or is a +@code{void} type. + +@item __is_enum (type) +If @code{type} is a cv enumeration type ([basic.compound]) the the trait is +true, else it is false. + +@item __is_pod (type) +If @code{type} is a cv POD type ([basic.types]) then the trait is true, +else it is false. Requires: @code{type} shall be a complete type, +an array type of unknown bound, or is a @code{void} type. + +@item __is_polymorphic (type) +If @code{type} is a polymorphic class ([class.virtual]) then the trait +is true, else it is false. Requires: @code{type} shall be a complete +type, an array type of unknown bound, or is a @code{void} type. + +@item __is_union (type) +If @code{type} is a cv union type ([basic.compound]) the the trait is +true, else it is false. + +@end table + @node Java Exceptions @section Java Exceptions |