https://itanium-cxx-abi.github.io/cxx-abi/

Itanium C++ ABI

Revised March 14, 2017

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Introduction

The Itanium C++ ABI is an ABI for C++. As an ABI, it gives precise rules for implementing the language, ensuring that separately-compiled parts of a program can successfully interoperate. Although it was initially developed for the Itanium architecture, it is not platform-specific and can be layered portably on top of an arbitrary C ABI. Accordingly, it is used as the standard C++ ABI for many major operating systems on all major architectures, and is implemented in many major C++ compilers, including GCC and Clang.

Contact

This website may be mirrored in many places, some of which may become stale. The current canonical location is:

• http://itanium-cxx-abi.github.io/cxx-abi/

The primary discussion forum for the ABI is the GitHub repository. Please open a new issue for any new topic you want to discuss. Previously, the ABI was discussed on a mailing list, cxx-abi-dev, whose archives are still accessible.

Drafts

 

• Draft C++ ABI for Itanium
• Draft psABI exception handling specification
• ABI Examples code samples and tests

   

• Sample GCC code:
  • typeinfo: class type_info declaration
  • cxxabi.h: ABI support type_info classes and prototypes
  • vec.cc: ABI vector new and delete helpers
  • tinfo.h: runtime header for tinfo.cc & tinfo2.cc
  • tinfo.cc: ABI dynamic cast and catch matching routines
  • tinfo2.cc: ABI non-class type_info definitions

Proposals and auxiliary information:

• Proposals to the base ABI group for COMDAT sections and removing limitations on section indices.
• SGI Interface Section proposal.
• Vtable layout examples.
• WG21 argument destruction writeup (PDF)

 

• Legacy open issues list
• Legacy closed issues list

   

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  Objectives

   

  • Interoperable C++ compilation on Itanium: we want users to be able to build relocatable objects with different compilers and link them together, and if possible even to ship common DSOs. This objective implies agreement on:
    • Data representation
    • Object file representation
    • Library API

     

  • ISO Standard C++: highest priority is functionality and performance of standard-compliant code. It should not be sacrificed for the benefit of language extensions or legacy implementations (though considering them as tie-breakers is fine).

     

  • Some areas will be easier to agree on than others. Our priorities should be based on achieving as much interoperability as possible if we can't attain perfection. That is, it is better to end up with a few restrictions being required for interoperable code, than to have no interoperability at all. This suggests priorities as follows:
    1. Items requiring base ABI changes that might affect other languages, and will therefore become impossible soon. Examples include exception handling / stack unwind, or ELF changes (not extensions).
    2. Core features where differences will prevent virtually any C++ object code from porting. Examples include data layout and calling conventions.
    3. Limited usage features, where users can achieve portability by avoiding the feature. An example might be multi-threading.
    4. Peripheral features, where the requirements on users to achieve portability are clear and easy to implement. An example is non-explicit inlining, where compilers would presumably allow it to just be suppressed.
    5. Tool interfaces, which affect how users build code, rather than what they build. An example is the compilation command line.

     

  • Mechanisms/methods which allow coexistence of incompatible implementations may be suitable in some cases. For instance, packaging vendor-specific compiler support runtimes in DSOs occupying distinct namespaces might allow multiple such DSOs to be loaded for mixed objects and avoid requiring that all vendors have the same support runtimes.

   

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  Action Item Status

   

  #	Action	Who	Status	Opened	Closed
  1	Distribute Sun C++ ABI	Mike Ball	closed	990603	990930
  2	Distribute Sun C++ ABI Rationale	Mike Ball	closed	990603	990930
  3	Distribute Taligent C++ ABI	Cary Coutant	moot	990603	991101
  4	Expedite Itanium RT Arch doc release	Cary Coutant	closed	990603	990720
  5	Set up n-way NDA for eligible members	Priti Shrivastav	open	990603
  6	Organize/summarize object layout issues and alternatives	Matt Austern	closed	990603	990624
  7	Write-up of Vfunc call protocol	Christophe de Dinechin	closed	990610	990805
  8	Write-up of object layout strawman	Matt Austern	closed	990610	990624
  9	Check with c++-core about empty base placement	Jason Merrill	closed	990610	990618
  10	Describe dynamic cast / inaccessible base issue	Daveed Vandevoorde	closed	990617	990701
  11	Summarize ctor/dtor issues	Michael Lam	closed	990617	990729
  12	Describe Intel exception model	Priti Shrivastav	closed	990624	990818
  13	Propose RTTI representation	Daveed Vandevoorde	closed	990701	990819
  14	Open EDG exception stack?	Daveed Vandevoorde	moot	990715	990930
  15	Priority scheme descriptor for C-2	Jim Dehnert	closed	990715	990804
  16	Covariant return scheme	Jason Merrill	closed	990715	990729
  17	Validate Christophe's B-6 Vtable layout	Jim Dehnert	closed	990729	990811
  18	Check Sun dynamic cast algorithm	Michael Lam	closed	990805	990812
  19	Write up C-3 destructor proposal	Jim Dehnert	closed	990805	990811
  20	Look at implications of discussion on B-1, B-6	Christophe de Dinechin	closed	990812	990830
  21	Look at alternative implementations of C-2	Jim Dehnert	closed	990812	991110
  22	Describe HP hash processing for RTTI	Christophe de Dinechin	moot	990826	990930
  23	Complete RTTI proposal	Daveed Vandevoorde	closed	990826	991006
  24	Summarize Vtable issues	Jason Merrill	closed	990909	990930
  25	Update traceback personality API	Christophe de Dinechin	closed	990923	000105
  26	Push COMDAT to base ABI group	Jim Dehnert	closed	991014	000317
  27	Writeup Vtable Changes	Jason Merrill	closed	991014	991021
  28	Write Virtual destructor proposal	Christophe de Dinechin	closed	991014	000217
  29	dynamic_cast pseudocode	Jason Merrill	closed	991028	000712
  30	Mangling proposal	Daveed Vandevoorde	closed	991028	000118
  31	Construction vtable writeup	Coleen Phillimore	closed	000127	000216
  32	Raise sorting issue C-2 with base ABI group	Jim Dehnert	closed	991202	000717
  33	long double in psABI	Christophe de Dinechin	closed	000210	0003xx
  34	incomplete_type_info proposal	Christophe de Dinechin	closed	000210	000316
  35	new array cookie writeup	Matt Austern	closed	000210	000217
  36	Mangling document update	Daveed Vandevoorde	closed	000210	000217
  37	Validate utility of has-public-base	Nathan Sidwell	closed	000218	000705

   

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  Issue Status

  In the following table, the class column attempts to classify the issue on the basis of what it likely affects. The identifiers used are:

  call	Function call interface, i.e. call linkage
  data	Data layout
  lib	Runtime library support
  lif	Library interface, i.e. API
  g	Potential gABI impact
  ps	Potential psABI impact
  source	Source code conventions (i.e. API, not ABI)
  tools	May affect how program construction tools interact

   

  ---

  #	Issue	Class	Status	Source	Opened	Closed
  A	Object Layout
  A-1	Vptr location	data	closed	SGI	990520	990624
  A-2	Virtual base classes	data	closed	SGI	990520	990624
  A-3	Multiple inheritance	data	closed	SGI	990520	990701
  A-4	Empty base classes	data	closed	SGI	990520	990624
  A-5	Empty parameters	data	closed	SGI	990520	001117
  A-6	RTTI (type_info) .o representation	data call ps	closed	SGI	990520	991028
  A-7	Vptr sharing with primary base class	data	closed	HP	990603	990729
  A-8	(Virtual) base class alignment	data	closed	HP	990603	990624
  A-9	Sorting fields as allowed by [class.mem]/12	data	closed	HP	990603	990624
  A-10	Class parameters in registers	call	closed	HP	990603	990701
  A-11	Pointers to member functions	data	closed	Cygnus	990603	990812
  A-12	Merging secondary vtables	data	closed	Sun	990610	990805
  A-13	Parameter struct field promotion	call	closed	SGI	990603	990701
  A-14	Pointers to data members	data	closed	SGI	990729	990805
  A-15	Empty bit-fields	data	closed	CodeSourcery	991214	000106
  A-16	Nearly empty virtual bases	data	closed	SGI	991228	000106
  A-17	Primary indirect virtual base allocation	data	closed	SGI	991228	000113
  A-18	Virtual base alignment	data	closed	SGI	991228	000113
  A-19	Primary indirect virtual base choice	data	closed	All	000106	000120
  A-20	Operator new array cookies	data	closed	All	000113	000120
  A-21	Placement new array cookies	data	closed	All	000113	000217
  A-22	RTTI for reference types	data	closed	CodeSourcery	000119	000203
  A-23	RTTI class descriptors	data	closed	CodeSourcery	000124	000302
  A-24	RTTI for incomplete types	data	closed	CodeSourcery	000126	000330
  A-25	Excess-width bitfields	data	closed	IBM	000204	000217
  A-26	NULL pointers to member functions	data	closed	CodeSourcery	000221	000302
  A-27	NULL pointers to data members	data	closed	CodeSourcery	000222	000302
  A-28	RTTI equality testing	data	closed	CodeSourcery	000406	000504
  A-29	RTTI pointer-to-member	data	closed	CodeSourcery	000407	000504
  A-30	RTTI portability	data	closed	HUB	001012	001109
  A-31	Overlaying tail padding	data	closed	CodeSourcery	001019	001109
  B	Virtual Function Handling
  B-1	Adjustment of "this" pointer (e.g. thunks)	data call	closed	SGI	990520	991202
  B-2	Covariant return types	call	closed	SGI	990520	990722
  B-3	Allowed caching of vtable contents	call	closed	HP	990603	990805
  B-4	Function descriptors in vtable	data	closed	HP	990603	990805
  B-5	Where are vtables emitted?	data	closed	HP	990603	991118
  B-6	Virtual function table layout	data	closed	SGI	990520	991028
  B-7	Objects and Vtables in shared memory	data	closed	HP	990624	990805
  B-8	dynamic_cast	data	closed	SGI	990628	991014
  B-9	Primary base vtable embedding	data	closed	Cygnus	000217	000302
  B-10	Pure virtual runtime	call	closed	CodeSourcery	000629	000706
  C	Object Construction/Destruction
  C-1	Interaction with .init/.fini	lif ps	closed	SGI	990520	991202
  C-2	Order of ctors/dtors w.r.t. link	lif ps	closed	HP	990603	000817
  C-3	Order of ctors/dtors w.r.t. DSOs	ps	closed	HP	990603	000504
  C-4	Construction vtables	call	closed	Cygnus	990603	000504
  C-5	Calling virtual destructors	call	closed	Sun	990603	991104
  C-6	Extra parameters to ctors/dtors	call	closed	Cygnus	990603	991104
  C-7	Passing value parameters by reference	call	closed	All	990625	990805
  C-8	Returning classes with non-trival copy constructors	call	closed	All	990625	990722
  C-9	Passing parameters with ctors/dtors	call	closed	All	991028	991104
  C-10	Synthesized copy assignments	call	closed	All	991028	991028
  C-11	Array constructors/destructors	call	closed	Cygnus	000130	000309
  C-12	Constructor return values	call	closed	Cygnus	000130	000309
  C-13	Allocating constructors	call	closed	HP	000309	000803
  C-14	Local-scope dynamic constructors	data	closed	all	000309	000511
  C-15	Alternate array allocators	call	closed	CodeSourcery	000628	000720
  C-16	Copy constructor runtime	call	closed	CodeSourcery	000628	000720
  C-17	Uncatch exception runtime	call	table	all	000706	000720
  C-18	Result buffers	call	closed	SGI	000724	000817
  C-19	NULL ctor/dtor API parameters	call	closed	CodeSourcery	000806	000831
  D	Exception Handling
  D-0	Exception handling framework	lib ps	closed	SGI	990520	991216
  D-1	Language-specific data area format	lib ps	open	SGI	990520
  D-2	Unwind personality routines	lib ps	closed	SGI	990520	000106
  D-3	Unwind process clarification	lib ps	closed	SGI	990520	000106
  D-4	Unwind routines nested?	lib ps	closed	SGI	990520	991209
  D-5	Interaction with other languages (e.g. Java)	lib ps	closed	HP	990603	991007
  D-6	Allow resumption in other languages?	lib ps	closed	HP	990603	991007
  D-7	Interaction with signals or asynch events	lib ps	closed	HP	990603	991209
  D-8	Interaction with threads packages	lib ps	closed	SGI	990603	000106
  D-9	longjmp interaction	lib ps	closed	HP	990908	000113
  D-10	psABI proposal	lib ps	closed	all	991216	000120
  D-11	pthreads interface	lib ps	closed	all	991216	000203
  D-12	Table location	lib ps	closed	all	991216	000504
  D-13	_Unwind_ForcedUnwind	lib ps	closed	all	991216	000120
  D-14	__cxa_begin/end_catch	lib	closed	all	991216	001109
  D-15	Terminate handler and threads	lib	closed	all	991216	000106
  D-16	Exception specifications	lib	closed	all	991216	000113
  D-17	bad_cast, bad_typeid runtime	call	closed	CodeSourcery	000629	000706
  D-18	__cxa_throw_type_info	lib	closed	all	001012	001109
  E	Template Instantiation Model
  E-1	When does instantiation occur?	tools	closed	SGI	990520	000511
  E-2	Export template model	tools	tabled	SGI	990520
  E-3	Template repository	tools	closed	HP	990603	000511
  F	Name Mangling
  F-1	Mangling convention	call	closed	SGI	990520	000330
  F-2	Mangled name size	call g	closed	SGI	990520	000511
  F-3	Consistency checks	call g	tabled	SGI	990520
  F-4	Empty throw specs	call g	tabled	HP	990930
  F-5	ILP32 vs. LP64	call	closed	HP	000210	000824
  F-6	Demangling	lib	closed	Cygnus	000210	000504
  F-7	Mangling statics	call	closed	HP	000223	000504
  F-8	Identifiers with unicode letters	call	closed	HU-Berlin	000323	000413
  F-9	Strings with unicode letters	call	closed	HU-Berlin	000323	000413
  F-10	Mangling function return types	call	closed	all	000330	000413
  F-11	Hash for local strings	call	closed	all	000330	000504
  G	Miscellaneous
  G-1	Basic command line options	tools	closed	HP	990603	000824
  G-2	Detection of 1-def rule violations	call	closed	Sun	990603	000504
  G-3	Inlined routine linkage	call	closed	Sun	990603	991202
  G-4	Dynamic init of local static objects and multithreading	call	closed	SCO	990607	001109
  G-5	Varargs routine interface	call	closed	HU-B	990810	991014
  G-6	bool parameters	call	closed	all	991104	991202
  H	Runtime Library Interface
  H-1	Runtime library DSO name	tools	closed	SGI	990616	000817
  H-2	Runtime library API	lif	tabled	SGI	990616

   

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来源： https://www.cnblogs.com/Searchor/p/14023790.html