cxxabi.h
Go to the documentation of this file.
// ABI Support -*- C++ -*-
// Copyright (C) 2000-2025 Free Software Foundation, Inc.
//
// This file is part of GCC.
//
// GCC is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation; either version 3, or (at your option)
// any later version.
//
// GCC is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
// GNU General Public License for more details.
//
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively. If not, see
// <http://www.gnu.org/licenses/>.
// Written by Nathan Sidwell, Codesourcery LLC, <nathan@codesourcery.com>
/* This file declares the new abi entry points into the runtime. It is not
normally necessary for user programs to include this header, or use the
entry points directly. However, this header is available should that be
needed.
Some of the entry points are intended for both C and C++, thus this header
is includable from both C and C++. Though the C++ specific parts are not
available in C, naturally enough. */
/** @file cxxabi.h
* The header provides an interface to the C++ ABI.
*/
#ifndef _CXXABI_H
#define _CXXABI_H 1
#ifdef _GLIBCXX_SYSHDR
#pragma GCC system_header
#endif
#pragma GCC visibility push(default)
#include <stddef.h>
#include <bits/c++config.h>
#include <bits/cxxabi_tweaks.h>
#include <bits/cxxabi_forced.h>
#include <bits/cxxabi_init_exception.h>
#ifdef __cplusplus
namespace __cxxabiv1
{
extern "C"
{
#endif
typedef __cxa_cdtor_return_type (*__cxa_cdtor_type)(void *);
// Allocate array.
void*
__cxa_vec_new(size_t __element_count, size_t __element_size,
size_t __padding_size, __cxa_cdtor_type __constructor,
__cxa_cdtor_type __destructor);
void*
__cxa_vec_new2(size_t __element_count, size_t __element_size,
size_t __padding_size, __cxa_cdtor_type __constructor,
__cxa_cdtor_type __destructor, void *(*__alloc) (size_t),
void (*__dealloc) (void*));
void*
__cxa_vec_new3(size_t __element_count, size_t __element_size,
size_t __padding_size, __cxa_cdtor_type __constructor,
__cxa_cdtor_type __destructor, void *(*__alloc) (size_t),
void (*__dealloc) (void*, size_t));
// Construct array.
__cxa_vec_ctor_return_type
__cxa_vec_ctor(void* __array_address, size_t __element_count,
size_t __element_size, __cxa_cdtor_type __constructor,
__cxa_cdtor_type __destructor);
__cxa_vec_ctor_return_type
__cxa_vec_cctor(void* __dest_array, void* __src_array,
size_t __element_count, size_t __element_size,
__cxa_cdtor_return_type (*__constructor) (void*, void*),
__cxa_cdtor_type __destructor);
// Destruct array.
void
__cxa_vec_dtor(void* __array_address, size_t __element_count,
size_t __element_size, __cxa_cdtor_type __destructor);
void
__cxa_vec_cleanup(void* __array_address, size_t __element_count, size_t __s,
__cxa_cdtor_type __destructor) _GLIBCXX_NOTHROW;
// Destruct and release array.
void
__cxa_vec_delete(void* __array_address, size_t __element_size,
size_t __padding_size, __cxa_cdtor_type __destructor);
void
__cxa_vec_delete2(void* __array_address, size_t __element_size,
size_t __padding_size, __cxa_cdtor_type __destructor,
void (*__dealloc) (void*));
void
__cxa_vec_delete3(void* __array_address, size_t __element_size,
size_t __padding_size, __cxa_cdtor_type __destructor,
void (*__dealloc) (void*, size_t));
int
__cxa_guard_acquire(__guard*);
void
__cxa_guard_release(__guard*) _GLIBCXX_NOTHROW;
void
__cxa_guard_abort(__guard*) _GLIBCXX_NOTHROW;
// DSO destruction.
int
#ifdef _GLIBCXX_CDTOR_CALLABI
__cxa_atexit(void (_GLIBCXX_CDTOR_CALLABI *)(void*), void*, void*) _GLIBCXX_NOTHROW;
#else
__cxa_atexit(void (*)(void*), void*, void*) _GLIBCXX_NOTHROW;
#endif
void
__cxa_finalize(void*);
// TLS destruction.
int
#ifdef _GLIBCXX_CDTOR_CALLABI
__cxa_thread_atexit(void (_GLIBCXX_CDTOR_CALLABI *)(void*), void*, void *) _GLIBCXX_NOTHROW;
#else
__cxa_thread_atexit(void (*)(void*), void*, void *) _GLIBCXX_NOTHROW;
#endif
// Pure virtual functions.
void
__cxa_pure_virtual(void) __attribute__ ((__noreturn__));
void
__cxa_deleted_virtual(void) __attribute__ ((__noreturn__));
// Exception handling auxiliary.
void
__cxa_bad_cast() __attribute__((__noreturn__));
void
__cxa_bad_typeid() __attribute__((__noreturn__));
void
__cxa_throw_bad_array_new_length() __attribute__((__noreturn__));
/**
* @brief Demangling routine.
* ABI-mandated entry point in the C++ runtime library for demangling.
*
* @param __mangled_name A NUL-terminated character string
* containing the name to be demangled.
*
* @param __output_buffer A region of memory, allocated with
* malloc, of @a *__length bytes, into which the demangled name is
* stored. If @a __output_buffer is not long enough, it is
* expanded using realloc. @a __output_buffer may instead be null;
* in that case, the demangled name is placed in a region of memory
* allocated with malloc.
*
* @param __length If @a __length is non-null, the length of the
* buffer containing the demangled name is placed in @a *__length.
*
* @param __status If @a __status is non-null, @a *__status is set to
* one of the following values:
* 0: The demangling operation succeeded.
* -1: A memory allocation failure occurred.
* -2: @a mangled_name is not a valid name under the C++ ABI mangling rules.
* -3: One of the arguments is invalid.
*
* @return A pointer to the start of the NUL-terminated demangled
* name, or a null pointer if the demangling fails. The caller is
* responsible for deallocating this memory using @c free.
*
* The demangling is performed using the C++ ABI mangling rules,
* with GNU extensions. For example, this function is used in
* __gnu_cxx::__verbose_terminate_handler.
*
* See https://gcc.gnu.org/onlinedocs/libstdc++/manual/ext_demangling.html
* for other examples of use.
*
* @note The same demangling functionality is available via
* libiberty (@c <libiberty/demangle.h> and @c libiberty.a) in GCC
* 3.1 and later, but that requires explicit installation (@c
* --enable-install-libiberty) and uses a different API, although
* the ABI is unchanged.
*/
char*
__cxa_demangle(const char* __mangled_name, char* __output_buffer,
size_t* __length, int* __status);
#ifdef __cplusplus
}
} // namespace __cxxabiv1
#endif
#ifdef __cplusplus
#include <typeinfo>
namespace __cxxabiv1
{
// Type information for int, float etc.
class __fundamental_type_info : public std::type_info
{
public:
explicit
__fundamental_type_info(const char* __n) : std::type_info(__n) { }
virtual
~__fundamental_type_info();
};
// Type information for array objects.
class __array_type_info : public std::type_info
{
public:
explicit
__array_type_info(const char* __n) : std::type_info(__n) { }
virtual
~__array_type_info();
};
// Type information for functions (both member and non-member).
class __function_type_info : public std::type_info
{
public:
explicit
__function_type_info(const char* __n) : std::type_info(__n) { }
virtual
~__function_type_info();
protected:
// Implementation defined member function.
virtual bool
__is_function_p() const;
};
// Type information for enumerations.
class __enum_type_info : public std::type_info
{
public:
explicit
__enum_type_info(const char* __n) : std::type_info(__n) { }
virtual
~__enum_type_info();
};
// Common type information for simple pointers and pointers to member.
class __pbase_type_info : public std::type_info
{
public:
unsigned int __flags; // Qualification of the target object.
const std::type_info* __pointee; // Type of pointed to object.
explicit
__pbase_type_info(const char* __n, int __quals,
const std::type_info* __type)
: std::type_info(__n), __flags(__quals), __pointee(__type)
{ }
virtual
~__pbase_type_info();
// Implementation defined type.
enum __masks
{
__const_mask = 0x1,
__volatile_mask = 0x2,
__restrict_mask = 0x4,
__incomplete_mask = 0x8,
__incomplete_class_mask = 0x10,
__transaction_safe_mask = 0x20,
__noexcept_mask = 0x40
};
protected:
__pbase_type_info(const __pbase_type_info&);
__pbase_type_info&
operator=(const __pbase_type_info&);
// Implementation defined member functions.
virtual bool
__do_catch(const std::type_info* __thr_type, void** __thr_obj,
unsigned int __outer) const;
inline virtual bool
__pointer_catch(const __pbase_type_info* __thr_type, void** __thr_obj,
unsigned __outer) const;
};
inline bool __pbase_type_info::
__pointer_catch (const __pbase_type_info *thrown_type,
void **thr_obj,
unsigned outer) const
{
return __pointee->__do_catch (thrown_type->__pointee, thr_obj, outer + 2);
}
// Type information for simple pointers.
class __pointer_type_info : public __pbase_type_info
{
public:
explicit
__pointer_type_info(const char* __n, int __quals,
const std::type_info* __type)
: __pbase_type_info (__n, __quals, __type) { }
virtual
~__pointer_type_info();
protected:
// Implementation defined member functions.
virtual bool
__is_pointer_p() const;
virtual bool
__pointer_catch(const __pbase_type_info* __thr_type, void** __thr_obj,
unsigned __outer) const;
};
class __class_type_info;
// Type information for a pointer to member variable.
class __pointer_to_member_type_info : public __pbase_type_info
{
public:
__class_type_info* __context; // Class of the member.
explicit
__pointer_to_member_type_info(const char* __n, int __quals,
const std::type_info* __type,
__class_type_info* __klass)
: __pbase_type_info(__n, __quals, __type), __context(__klass) { }
virtual
~__pointer_to_member_type_info();
protected:
__pointer_to_member_type_info(const __pointer_to_member_type_info&);
__pointer_to_member_type_info&
operator=(const __pointer_to_member_type_info&);
// Implementation defined member function.
virtual bool
__pointer_catch(const __pbase_type_info* __thr_type, void** __thr_obj,
unsigned __outer) const;
};
// Helper class for __vmi_class_type.
class __base_class_type_info
{
public:
const __class_type_info* __base_type; // Base class type.
#ifdef _GLIBCXX_LLP64
long long __offset_flags; // Offset and info.
#else
long __offset_flags; // Offset and info.
#endif
enum __offset_flags_masks
{
__virtual_mask = 0x1,
__public_mask = 0x2,
__hwm_bit = 2,
__offset_shift = 8 // Bits to shift offset.
};
// Implementation defined member functions.
bool
__is_virtual_p() const
{ return __offset_flags & __virtual_mask; }
bool
__is_public_p() const
{ return __offset_flags & __public_mask; }
ptrdiff_t
__offset() const
{
// This shift, being of a signed type, is implementation
// defined. GCC implements such shifts as arithmetic, which is
// what we want.
return static_cast<ptrdiff_t>(__offset_flags) >> __offset_shift;
}
};
// Type information for a class.
class __class_type_info : public std::type_info
{
public:
explicit
__class_type_info (const char *__n) : type_info(__n) { }
virtual
~__class_type_info ();
// Implementation defined types.
// The type sub_kind tells us about how a base object is contained
// within a derived object. We often do this lazily, hence the
// UNKNOWN value. At other times we may use NOT_CONTAINED to mean
// not publicly contained.
enum __sub_kind
{
// We have no idea.
__unknown = 0,
// Not contained within us (in some circumstances this might
// mean not contained publicly)
__not_contained,
// Contained ambiguously.
__contained_ambig,
// Via a virtual path.
__contained_virtual_mask = __base_class_type_info::__virtual_mask,
// Via a public path.
__contained_public_mask = __base_class_type_info::__public_mask,
// Contained within us.
__contained_mask = 1 << __base_class_type_info::__hwm_bit,
__contained_private = __contained_mask,
__contained_public = __contained_mask | __contained_public_mask
};
struct __upcast_result;
struct __dyncast_result;
protected:
// Implementation defined member functions.
virtual bool
__do_upcast(const __class_type_info* __dst_type, void**__obj_ptr) const;
virtual bool
__do_catch(const type_info* __thr_type, void** __thr_obj,
unsigned __outer) const;
public:
// Helper for upcast. See if DST is us, or one of our bases.
// Return false if not found, true if found.
virtual bool
__do_upcast(const __class_type_info* __dst, const void* __obj,
__upcast_result& __restrict __result) const;
// Indicate whether SRC_PTR of type SRC_TYPE is contained publicly
// within OBJ_PTR. OBJ_PTR points to a base object of our type,
// which is the destination type. SRC2DST indicates how SRC
// objects might be contained within this type. If SRC_PTR is one
// of our SRC_TYPE bases, indicate the virtuality. Returns
// not_contained for non containment or private containment.
inline __sub_kind
__find_public_src(ptrdiff_t __src2dst, const void* __obj_ptr,
const __class_type_info* __src_type,
const void* __src_ptr) const;
// Helper for dynamic cast. ACCESS_PATH gives the access from the
// most derived object to this base. DST_TYPE indicates the
// desired type we want. OBJ_PTR points to a base of our type
// within the complete object. SRC_TYPE indicates the static type
// started from and SRC_PTR points to that base within the most
// derived object. Fill in RESULT with what we find. Return true
// if we have located an ambiguous match.
virtual bool
__do_dyncast(ptrdiff_t __src2dst, __sub_kind __access_path,
const __class_type_info* __dst_type, const void* __obj_ptr,
const __class_type_info* __src_type, const void* __src_ptr,
__dyncast_result& __result) const;
// Helper for find_public_subobj. SRC2DST indicates how SRC_TYPE
// bases are inherited by the type started from -- which is not
// necessarily the current type. The current type will be a base
// of the destination type. OBJ_PTR points to the current base.
virtual __sub_kind
__do_find_public_src(ptrdiff_t __src2dst, const void* __obj_ptr,
const __class_type_info* __src_type,
const void* __src_ptr) const;
};
// Type information for a class with a single non-virtual base.
class __si_class_type_info : public __class_type_info
{
public:
const __class_type_info* __base_type;
explicit
__si_class_type_info(const char *__n, const __class_type_info *__base)
: __class_type_info(__n), __base_type(__base) { }
virtual
~__si_class_type_info();
protected:
__si_class_type_info(const __si_class_type_info&);
__si_class_type_info&
operator=(const __si_class_type_info&);
// Implementation defined member functions.
virtual bool
__do_dyncast(ptrdiff_t __src2dst, __sub_kind __access_path,
const __class_type_info* __dst_type, const void* __obj_ptr,
const __class_type_info* __src_type, const void* __src_ptr,
__dyncast_result& __result) const;
virtual __sub_kind
__do_find_public_src(ptrdiff_t __src2dst, const void* __obj_ptr,
const __class_type_info* __src_type,
const void* __sub_ptr) const;
virtual bool
__do_upcast(const __class_type_info*__dst, const void*__obj,
__upcast_result& __restrict __result) const;
};
// Type information for a class with multiple and/or virtual bases.
class __vmi_class_type_info : public __class_type_info
{
public:
unsigned int __flags; // Details about the class hierarchy.
unsigned int __base_count; // Number of direct bases.
// The array of bases uses the trailing array struct hack so this
// class is not constructable with a normal constructor. It is
// internally generated by the compiler.
__base_class_type_info __base_info[1]; // Array of bases.
explicit
__vmi_class_type_info(const char* __n, int ___flags)
: __class_type_info(__n), __flags(___flags), __base_count(0) { }
virtual
~__vmi_class_type_info();
// Implementation defined types.
enum __flags_masks
{
__non_diamond_repeat_mask = 0x1, // Distinct instance of repeated base.
__diamond_shaped_mask = 0x2, // Diamond shaped multiple inheritance.
__flags_unknown_mask = 0x10
};
protected:
// Implementation defined member functions.
virtual bool
__do_dyncast(ptrdiff_t __src2dst, __sub_kind __access_path,
const __class_type_info* __dst_type, const void* __obj_ptr,
const __class_type_info* __src_type, const void* __src_ptr,
__dyncast_result& __result) const;
virtual __sub_kind
__do_find_public_src(ptrdiff_t __src2dst, const void* __obj_ptr,
const __class_type_info* __src_type,
const void* __src_ptr) const;
virtual bool
__do_upcast(const __class_type_info* __dst, const void* __obj,
__upcast_result& __restrict __result) const;
};
// Exception handling forward declarations.
struct __cxa_exception;
struct __cxa_refcounted_exception;
struct __cxa_dependent_exception;
struct __cxa_eh_globals;
extern "C"
{
// Dynamic cast runtime.
// src2dst has the following possible values
// >-1: src_type is a unique public non-virtual base of dst_type
// dst_ptr + src2dst == src_ptr
// -1: unspecified relationship
// -2: src_type is not a public base of dst_type
// -3: src_type is a multiple public non-virtual base of dst_type
void*
__dynamic_cast(const void* __src_ptr, // Starting object.
const __class_type_info* __src_type, // Static type of object.
const __class_type_info* __dst_type, // Desired target type.
ptrdiff_t __src2dst); // How src and dst are related.
// Exception handling runtime.
// The __cxa_eh_globals for the current thread can be obtained by using
// either of the following functions. The "fast" version assumes at least
// one prior call of __cxa_get_globals has been made from the current
// thread, so no initialization is necessary.
__cxa_eh_globals*
__cxa_get_globals() _GLIBCXX_NOTHROW __attribute__ ((__const__));
__cxa_eh_globals*
__cxa_get_globals_fast() _GLIBCXX_NOTHROW __attribute__ ((__const__));
// Free the space allocated for the primary exception.
void
__cxa_free_exception(void*) _GLIBCXX_NOTHROW;
// Throw the exception.
void
__cxa_throw(void*, std::type_info*, void (_GLIBCXX_CDTOR_CALLABI *) (void *))
__attribute__((__noreturn__));
// Used to implement exception handlers.
void*
__cxa_get_exception_ptr(void*) _GLIBCXX_NOTHROW __attribute__ ((__pure__));
void*
__cxa_begin_catch(void*) _GLIBCXX_NOTHROW;
void
__cxa_end_catch();
void
__cxa_rethrow() __attribute__((__noreturn__));
// Returns the type_info for the currently handled exception [15.3/8], or
// null if there is none.
std::type_info*
__cxa_current_exception_type() _GLIBCXX_NOTHROW __attribute__ ((__pure__));
// GNU Extensions.
// Allocate memory for a dependent exception.
__cxa_dependent_exception*
__cxa_allocate_dependent_exception() _GLIBCXX_NOTHROW;
// Free the space allocated for the dependent exception.
void
__cxa_free_dependent_exception(__cxa_dependent_exception*) _GLIBCXX_NOTHROW;
} // extern "C"
// A magic placeholder class that can be caught by reference
// to recognize foreign exceptions.
class __foreign_exception
{
virtual ~__foreign_exception() throw();
virtual void __pure_dummy() = 0; // prevent catch by value
};
} // namespace __cxxabiv1
/** @namespace abi
* @brief The cross-vendor C++ Application Binary Interface. A
* namespace alias to __cxxabiv1, but user programs should use the
* alias 'abi'.
*
* A brief overview of an ABI is given in the libstdc++ FAQ, question
* 5.8 (you may have a copy of the FAQ locally, or you can view the online
* version at http://gcc.gnu.org/onlinedocs/libstdc++/faq.html#5_8 ).
*
* GCC subscribes to a cross-vendor ABI for C++, sometimes
* called the IA64 ABI because it happens to be the native ABI for that
* platform. It is summarized at http://www.codesourcery.com/cxx-abi/
* along with the current specification.
*
* For users of GCC greater than or equal to 3.x, entry points are
* available in <cxxabi.h>, which notes, <em>'It is not normally
* necessary for user programs to include this header, or use the
* entry points directly. However, this header is available should
* that be needed.'</em>
*/
namespace abi = __cxxabiv1;
namespace __gnu_cxx
{
/**
* @brief Exception thrown by __cxa_guard_acquire.
* @ingroup exceptions
*
* C++ 2011 6.7 [stmt.dcl]/4: If control re-enters the declaration
* recursively while the variable is being initialized, the behavior
* is undefined.
*
* Since we already have a library function to handle locking, we might
* as well check for this situation and throw an exception.
* We use the second byte of the guard variable to remember that we're
* in the middle of an initialization.
*/
class recursive_init_error: public std::exception
{
public:
recursive_init_error() _GLIBCXX_NOTHROW;
virtual ~recursive_init_error() _GLIBCXX_NOTHROW;
};
}
#endif // __cplusplus
#pragma GCC visibility pop
#endif // __CXXABI_H
__cxxabiv1::__cxa_demangle
char * __cxa_demangle(const char *__mangled_name, char *__output_buffer, size_t *__length, int *__status)
Demangling routine. ABI-mandated entry point in the C++ runtime library for demangling.
typeinfo
cxxabi_init_exception.h
cxxabi_forced.h
cxxabi_tweaks.h
c++config.h
__gnu_cxx
GNU extensions for public use.
abi
The cross-vendor C++ Application Binary Interface. A namespace alias to __cxxabiv1,...
__gnu_debug::__base
constexpr _Iterator __base(_Iterator __it)
Definition helper_functions.h:320
std::exception
Base class for all library exceptions.
Definition exception.h:62