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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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It holds the following function pointer entries, following those of any primary base’s virtual table, in the virtual functions’ declaration order: Type arguments appear using their regular encoding. The name member function returns the address of an NTBS, unique to the type, containing the mangled name of the type. Unsourced material may be challenged and removed. In cases where multiple order-insensitive abk are present, they should be ordered ‘K’ closest to the base type’V’, ‘r’, and ‘U’ farthest from the base typewith the ‘U’ qualifiers in alphabetical order by the vendor name with alphabetically earlier names closer to the base type.

Added non-virtual function calling conventions.

Initialization Initialize sizeof C to zero, align C to one, dsize C to zero. These tests are implemented by abi:: An implementation must satisfy this constraint, e. Statements consisting only of original research should be removed. The entries for virtual destructors are actually pairs of entries. The problem is that a complete object of a proper base class and a complete object of a derived class do not have virtual bases at the same offsets. Further, requiring a particular form of mangling would cause issues for systems where implementation limits e.


There are, however, some special cases.

For other types, they must be emitted at the location where their use is implied: Therefore, its virtual base offset for S in its embedded T-in-W virtual table is the only one present. Fix member function pointer description no division by two.

Since the Standard requires a virtual destructor, and it will rarely be called, it is a good candidate for this role. The types are substantively different if B is a morally virtual base of D or if B is not located at offset zero in D. Qualified names are encoded as: Meaning of error indications: The mangled symbols in this example, in the comments below the respective identifier name, are those produced by the GNU GCC 3.

c++ – To what extent does the Itanium ABI really specify padding and alignment? – Stack Overflow

The discriminator is used only for the second and later occurrences of the same “top-level” name within a single function since “unnamed abbi are distinctly numbered, they never include a discriminator. Function types not appearing ihanium part of a function name mangling, e. That is, user-defined constructors itanihm destructors, unless the function is declared inline, or has internal linkage, are emitted where defined, with their complete, and base object variants.

Hence, an earlier scheme of providing a hash-table into the list of base classes as is done e. 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. Secondary virtual pointers may be required for base classes that do not require secondary VTTs. No entity is added to the dictionary twice. Added one-time initialization API 3. Initialization entries with the same priority from different files or from other sources such as link command options will be executed in an unspecified order.


Non-template function names do not have return types encoded. The components and their meanings are as follows: Ittanium class is virtual 0x2: E” construct is used to describe a qualified name.

Name mangling

An implementation for a bit ABI would typically just change the sizes of members as appropriate i. There are two exceptions that appear to be substitution candidates from the grammar, but are explicitly excluded: For example, suppose we have the following hierarchy: Pointer-to-member types encode the class and qbi types.

Binary code compatibility Foreign function interface Language binding Linker dynamic Loader Year problem. An expression used as a template argument is delimited by “X String literals are encoded using their type, but not their value.

An implementation must only ensure that naming collisions are avoided. The VTT array is referenced via its own mangled external name, and the construction virtual tables are accessed via the VTT array, so the latter do not itaniuk external names.