Discussion and development of the “Itanium” portable C++ ABI used by many major C++ implementations. – Itanium C++ ABI. The Itanium ABI (which GCC uses) may specify these things (as within specifying ranges) Most types’ size and alignment is specified in the Intel System V ABI. Virtual Table Layout General A virtual table (vtable) is a table of information used to dispatch virtual functions, to ac.

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An implementation for a bit ABI would typically just change the sizes of members as appropriate i. Removing that requirement would not be a good idea, as there would then no longer be a way to emit all thunks with the functions they jump to.

This section identifies, for such itnium, where i.

Itanium C++ ABI

Other ABI aspects like exception handlingvirtual table layout, structure and stack frame paddingetc. It is expected that this will be the ‘natural’ order in most compilers.

One workaround for this is not to use ‘alias’ at all in which the method names typically need to be capitalized in C and Fortran. Therefore, any cross-references within the RTTI to types not known to be complete must be weak symbol references. Therefore function types always encode at least one parameter type, and function manglings can always be distinguished from data manglings by the presence of the type. Note that if the key function is not declared inline in the class definition, but its definition later is always declared inline, it will be emitted in every object containing the definition.

This class is always a satisfactory choice, since it is known to contain a definition of f. Both destroy any virtual bases; a separate, non-virtual function, called the base object destructor, performs destruction of the object but not its virtual base subobjects, and does not call delete. For a non-virtual base, this is the offset in the object of the base subobject.


Application binary interface – Wikipedia

When a virtual function is invoked via a virtual base, but has been overridden in a derived class, the overriding function first adds a fixed offset to adjust the this pointer to the virtual base, and then adds the value contained at the vcall offset in the virtual base to its this pointer to get the address of the derived object where the function was overridden.

Application binary interface Ai.

On other platforms, function pointers are represented as they would be in any other context. If present, components are present in the order described, except for the exceptions specified. A NULL iganium is represented as None of the above, i.

Name mangling

Reorganization of pointer RTTI. These values may be positive or negative.

When a complete object constructor is constructing a virtual base, it must be wary of using the vbase offsets in the virtual table, since the possibly shared virtual pointer may point to a construction virtual table of an unrelated base class. Those bases which do not have secondary virtual pointers in the VTT have their virtual pointers explicitly initialized to the main virtual table group by the constructors see Subobject Construction and Destruction.

The class has a virtual table for each proper base class that has a virtual table. The mangled name of a guard variable is the name of the guarded variable prefixed cc GV. Function types are composed from their parameter types and possibly the result type.


This ABI does not require an implementation to support this capability, but it specifies such a facility for those implementations that do.

Similarly, anonymous classes must have “fake” public names generated for them as the concept of anonymous classes only exists in the compiler, not the runtime. Note that this assumes that the same string literal occurring twice in a given function in fact represents a single entity, i. Then, this entry point must transfer control to itaniim non-adjusting entry point. In the object where instantiated, the virtual table, any subobject construction virtual tables, and the VTT, are emitted in a COMDAT identified by the virtual table mangled name.

The need arises where the language allows different entities to be named with the same identifier as long as they occupy a different namespace where a namespace is typically defined by otanium module, class, or explicit namespace directive or have different signatures such as function overloading. The operators are encoded using their usual encoding a two-letter code in most cases.

The first destructor, called aib complete object destructor, performs the destruction without calling delete on the object. No virtual base classes.

An existing compiler which uses thunks with a different means of adjusting the virtual table pointers can be made compliant with this ABI by only adding the vcall offsets — the thunks need not use them.

An expression used as a template argument is delimited by “X