116 lines
4.4 KiB
Plaintext
116 lines
4.4 KiB
Plaintext
@c Copyright (C) 2002 Free Software Foundation, Inc.
|
|
@c This is part of the GCC manual.
|
|
@c For copying conditions, see the file gcc.texi.
|
|
|
|
@node Compatibility
|
|
@chapter Binary Compatibility
|
|
@cindex binary compatibility
|
|
@cindex ABI
|
|
@cindex application binary interface
|
|
|
|
Binary compatibility encompasses several related concepts:
|
|
|
|
@table @dfn
|
|
@item application binary interface (ABI)
|
|
The set of runtime conventions followed by all of the tools that deal
|
|
with binary representations of a program, including compilers, assemblers,
|
|
linkers, and language runtime support.
|
|
Some ABIs are formal with a written specification, possibly designed
|
|
by multiple interested parties. Others are simply the way things are
|
|
actually done by a particular set of tools.
|
|
|
|
@item ABI conformance
|
|
A compiler conforms to an ABI if it generates code that follows all of
|
|
the specifications enumerated by that ABI@.
|
|
A library conforms to an ABI if it is implemented according to that ABI@.
|
|
An application conforms to an ABI if it is built using tools that conform
|
|
to that ABI and does not contain source code that specifically changes
|
|
behavior specified by the ABI@.
|
|
|
|
@item calling conventions
|
|
Calling conventions are a subset of an ABI that specify of how arguments
|
|
are passed and function results are returned.
|
|
|
|
@item interoperability
|
|
Different sets of tools are interoperable if they generate files that
|
|
can be used in the same program. The set of tools includes compilers,
|
|
assemblers, linkers, libraries, header files, startup files, and debuggers.
|
|
Binaries produced by different sets of tools are not interoperable unless
|
|
they implement the same ABI@. This applies to different versions of the
|
|
same tools as well as tools from different vendors.
|
|
|
|
@item intercallability
|
|
Whether a function in a binary built by one set of tools can call a
|
|
function in a binary built by a different set of tools is a subset
|
|
of interoperability.
|
|
|
|
@item implementation-defined features
|
|
Language standards include lists of implementation-defined features whose
|
|
behavior can vary from one implementation to another. Some of these
|
|
features are normally covered by a platform's ABI and others are not.
|
|
The features that are not covered by an ABI generally affect how a
|
|
program behaves, but not intercallability.
|
|
|
|
@item compatibility
|
|
Conformance to the same ABI and the same behavior of implementation-defined
|
|
features are both relevant for compatibility.
|
|
@end table
|
|
|
|
The application binary interface implemented by a C or C++ compiler
|
|
affects code generation and runtime support for:
|
|
|
|
@itemize @bullet
|
|
@item
|
|
size and alignment of data types
|
|
@item
|
|
layout of structured types
|
|
@item
|
|
calling conventions
|
|
@item
|
|
register usage conventions
|
|
@item
|
|
interfaces for runtime arithmetic support
|
|
@item
|
|
object file formats
|
|
@end itemize
|
|
|
|
In addition, the application binary interface implemented by a C++ compiler
|
|
affects code generation and runtime support for:
|
|
@itemize @bullet
|
|
@item
|
|
name mangling
|
|
@item
|
|
exception handling
|
|
@item
|
|
invoking constructors and destructors
|
|
@item
|
|
layout, alignment, and padding of classes
|
|
@item
|
|
layout and alignment of virtual tables
|
|
@end itemize
|
|
|
|
Some GCC compilation options cause the compiler to generate code that
|
|
does not conform to the platform's default ABI@. Other options cause
|
|
different program behavior for implementation-defined features that are
|
|
not covered by an ABI@. These options are provided for consistency with
|
|
other compilers that do not follow the platform's default ABI or the
|
|
usual behavior of implementation-defined features for the platform.
|
|
Be very careful about using such options.
|
|
|
|
Most platforms have a well-defined ABI that covers C code, but ABIs
|
|
that cover C++ functionality are not yet common.
|
|
|
|
Starting with GCC 3.2, GCC binary conventions for C++ are based on a
|
|
written, vendor-neutral C++ ABI that was designed to be specific to
|
|
64-bit Itanium but also includes generic specifications that apply to
|
|
any platform.
|
|
This C++ ABI is also implemented by other compiler vendors on some
|
|
platforms, notably GNU/Linux and BSD systems.
|
|
We have tried hard to provide a stable ABI that will be compatible with
|
|
future GCC releases, but it is possible that we will encounter problems
|
|
that make this difficult. Such problems could include different
|
|
interpretations of the C++ ABI by different vendors, bugs in the ABI, or
|
|
bugs in the implementation of the ABI in different compilers.
|
|
GCC's @code{-Wabi} switch warns when G++ generates code that is
|
|
probably not compatible with the C++ ABI@.
|