jau::type_info Class Reference

Generic type information using either Runtime type information (RTTI) or Compile time type information (CTTI) More...

#include <cpp_lang_util.hpp>

Collaboration diagram for jau::type_info:

Public Member Functions
	type_info () noexcept
	Constructor for an empty type_info instance, i.e. More...
	type_info (const char *signature_) noexcept
	Constructor using a const char* signature with a static storage duration. More...
	type_info (const std::type_info &info_) noexcept
	Constructor using an RTTI std::type_info reference, i.e. More...
std::string	demangled_name () const noexcept
	Return the demangle_name() of name(). More...
size_t	hash_code () const noexcept
	Returns an unspecified hash code of this instance. More...
const char *	name () const noexcept
	Returns the type name, compiler implementation specific. More...
bool	operator!= (const type_info &rhs) const noexcept
constexpr bool	operator== (const type_info &rhs) const noexcept
	Return true if both instances are equal. More...

Static Public Member Functions
static void	abort_invalid (const char *signature) noexcept
	Aborts program execution if given signature is nullptr or has a string length == 0. More...
static constexpr bool	is_valid (const char *signature) noexcept
	Returns true if given signature is not nullptr and has a string length > 0, otherwise false. More...

Static Public Attributes
static constexpr const bool	limited_lambda_id
	Static constexpr boolean indicating whether resulting type_info uniqueness is limited for lambda function types. More...

Detailed Description

Generic type information using either Runtime type information (RTTI) or Compile time type information (CTTI)

jau::type_info exposes same properties as RTTI std::type_index, i.e. can be used as index in associative and unordered associative containers and is CopyConstructible and CopyAssignable.

jau::type_info is compatible with std::type_index operations.

jau::type_info can be utilized w/o RTTI using Compile time type information (CTTI) information, i.e. JAU_PRETTY_FUNCTION via jau::ctti_name<R, L, A...>().

Consider using jau::make_ctti<R, L, A...>() for construction, as it removes the RTTI and CTTI code path differences.

RTTI and Compile time type information (CTTI) Natures

If RTTI is being used, see cxx_rtti_available, jau::type_info may be instantiated with a std::type_info reference as returned from typeid(T).

Without RTTI jau::type_info may be instantiated using JAU_PRETTY_FUNCTION. Hence utilizes Compile time type information (CTTI) only.

In both cases, jau::type_info will solely operate on the const char* signature and its hash value, aligning memory footprint and operations.

Use jau::make_ctti<R, L, A...>() for construction, as it removes the RTTI and CTTI code path differences.

Notes about lifecycle and identity

Prologue

We assume block scope and static storage duration (runtime lifecycle) of

• (1) [typeid(T)]((https://en.cppreference.com/w/cpp/language/typeid)
  • (1.1) The typeid expression is an lvalue expression which refers to an object with static storage duration.
  • (1.2) There is no guarantee that the same std::type_info instance will be referred to by all evaluations of the typeid expression on the same type, although they would compare equal.
• (2) JAU_PRETTY_FUNCTION, aka PRETTY_FUNCTION with properties of func
  • (2.1) This variable has block scope and static storage duration.

Equality Comparison

• compare the static name storage references (pointer) and return true if equal (fast path)
• due to (1.2), see above, the static name storage strings must be compared
  • compare the names' hash value and return false if not matching (fast path)
  • compare the static names' string and return the result (slow strcmp() equality)
    • this avoids a potential hash collision.

Limitations

Non unique lambda type names without RTTI using gcc or non clang compiler

Due to limitations of jau::make_ctti<R, L, A...>(), not using RTTI on gcc or non clang compiler will erroneously mistake different lambda functions defined within one function and using same function prototype R<A...> to be the same.

jau::type_info::limited_lambda_id exposes the potential limitation.

See also

Identity

jau::make_ctti<R, L, A...>

Examples

test_functional.hpp.

Definition at line 435 of file cpp_lang_util.hpp.

Constructor & Destructor Documentation

type_info() [1/3]

jau::type_info::type_info ( )

inlinenoexcept

Constructor for an empty type_info instance, i.e.

empty name() signature.

Definition at line 486 of file cpp_lang_util.hpp.

type_info() [2/3]

jau::type_info::type_info ( const std::type_info &  info_ )

inlinenoexcept

Constructor using an RTTI std::type_info reference, i.e.

typeid(T) result.

Consider using jau::make_ctti<R, L, A...>() for construction, as it removes the RTTI and CTTI code path differences.

Parameters

info_

RTTI std::type_info reference

See also

jau::make_ctti<R, L, A...>

Definition at line 500 of file cpp_lang_util.hpp.

type_info() [3/3]

jau::type_info::type_info ( const char *  signature_ )

inlinenoexcept

Constructor using a const char* signature with a static storage duration.

Aborts program execution if given signature is nullptr or has a string length == 0.

Parameters

signature_

valid string signature of type with length > 0 with static storage duration.

See also

jau::make_ctti<R, L, A...>

Definition at line 513 of file cpp_lang_util.hpp.

Member Function Documentation

is_valid()

static constexpr bool jau::type_info::is_valid ( const char *  signature )

inlinestaticconstexprnoexcept

Returns true if given signature is not nullptr and has a string length > 0, otherwise false.

Examples

test_functional.hpp.

Definition at line 468 of file cpp_lang_util.hpp.

Here is the caller graph for this function:

abort_invalid()

static void jau::type_info::abort_invalid ( const char *  signature )

inlinestaticnoexcept

Aborts program execution if given signature is nullptr or has a string length == 0.

Definition at line 473 of file cpp_lang_util.hpp.

operator==()

constexpr bool jau::type_info::operator== ( const type_info &  rhs ) const

inlineconstexprnoexcept

Return true if both instances are equal.

Parameters

rhs

Returns

See also

Identity

Definition at line 524 of file cpp_lang_util.hpp.

Here is the caller graph for this function:

operator!=()

bool jau::type_info::operator!= ( const type_info &  rhs ) const

inlinenoexcept

Definition at line 535 of file cpp_lang_util.hpp.

hash_code()

size_t jau::type_info::hash_code ( ) const

inlinenoexcept

Returns an unspecified hash code of this instance.

Properties

• for all type_info objects referring to the same type, their hash code is the same.
• type_info objects referring to different types may have the same hash code, i.e. due to hash collision.

Compatible with std::type_info definition.

Returns

Unspecified hash code of this instance.

See also

Identity

Definition at line 551 of file cpp_lang_util.hpp.

name()

const char * jau::type_info::name ( ) const

inlinenoexcept

Returns the type name, compiler implementation specific.

Examples

test_functional.hpp.

Definition at line 554 of file cpp_lang_util.hpp.

Here is the caller graph for this function:

demangled_name()

std::string jau::type_info::demangled_name ( ) const

inlinenoexcept

Return the demangle_name() of name().

Definition at line 558 of file cpp_lang_util.hpp.

Member Data Documentation

limited_lambda_id

constexpr const bool jau::type_info::limited_lambda_id

staticconstexpr

Initial value:

=
 
 
 
 
 
 
 
 
                        true

Static constexpr boolean indicating whether resulting type_info uniqueness is limited for lambda function types.

Always is false if rtti_available == true, i.e. lambda function types are always unique using RTTI.

May return true if:

• no RTTI and using gcc
• no RTTI and not using clang

See also

CTTI lambda name limitations

Examples

test_functional.hpp, and test_functional_perf.hpp.

Definition at line 454 of file cpp_lang_util.hpp.

---

The documentation for this class was generated from the following file:

• include/jau/cpp_lang_util.hpp