实际上你根本不需要ABI如果

你的程序没有函数，而且—— 你的程序是一个单独运行的可执行文件(即一个嵌入式系统)，它实际上是唯一在运行的东西，它不需要与其他任何东西对话。

过度简化的总结:

API:“这里是你可以调用的所有函数。” ABI:“这是调用函数的方法。”

ABI是编译器和链接器遵守的一组规则，以便编译您的程序，使其正常工作。ABIs涵盖多个主题:

Arguably the biggest and most important part of an ABI is the procedure call standard sometimes known as the "calling convention". Calling conventions standardize how "functions" are translated to assembly code. ABIs also dictate the how the names of exposed functions in libraries should be represented so that other code can call those libraries and know what arguments should be passed. This is called "name mangling". ABIs also dictate what type of data types can be used, how they must be aligned, and other low-level details.

更深入地了解调用约定，我认为它是ABI的核心:

机器本身没有“功能”的概念。当你用高级语言(如c)编写函数时，编译器会生成一行汇编代码，如_MyFunction1:。这是一个标签，它最终将被汇编程序解析为一个地址。这个标签标记了程序集代码中“函数”的“开始”。在高级代码中，当你“调用”这个函数时，你真正做的是导致CPU跳转到那个标签的地址并继续在那里执行。

在为跳转做准备时，编译器必须做一些重要的事情。调用约定就像一个清单，编译器遵循它来完成所有这些事情:

First, the compiler inserts a little bit of assembly code to save the current address, so that when your "function" is done, the CPU can jump back to the right place and continue executing. Next, the compiler generates assembly code to pass the arguments. Some calling conventions dictate that arguments should be put on the stack (in a particular order of course). Other conventions dictate that the arguments should be put in particular registers (depending on their data types of course). Still other conventions dictate that a specific combination of stack and registers should be used. Of course, if there was anything important in those registers before, those values are now overwritten and lost forever, so some calling conventions may dictate that the compiler should save some of those registers prior to putting the arguments in them. Now the compiler inserts a jump instruction telling the CPU to go to that label it made previously (_MyFunction1:). At this point, you can consider the CPU to be "in" your "function". At the end of the function, the compiler puts some assembly code that will make the CPU write the return value in the correct place. The calling convention will dictate whether the return value should be put into a particular register (depending on its type), or on the stack. Now it's time for clean-up. The calling convention will dictate where the compiler places the cleanup assembly code. Some conventions say that the caller must clean up the stack. This means that after the "function" is done and the CPU jumps back to where it was before, the very next code to be executed should be some very specific cleanup code. Other conventions say that the some particular parts of the cleanup code should be at the end of the "function" before the jump back.

有许多不同的abi /调用约定。主要有:

x86或x86-64 CPU(32位环境): CDECL STDCALL FASTCALL VECTORCALL THISCALL x86-64(64位环境): SYSTEMV MSNATIVE VECTORCALL ARM CPU(32位) AAPCS ARM处理器(64位) AAPCS64

这里有一个很棒的页面，它实际显示了为不同的abi编译时生成的程序集的差异。

另一件需要提及的事情是，ABI不仅仅与程序的可执行模块内部相关。链接器还使用它来确保程序正确调用库函数。您的计算机上运行着多个共享库，只要编译器知道它们各自使用的ABI，它就可以正确地从它们调用函数，而不会破坏堆栈。

编译器理解如何调用库函数是非常重要的。在一个托管平台上(也就是说，一个OS加载程序的平台)，如果不调用内核，您的程序甚至不能闪烁。

理解“ABI”的一个简单方法是将其与“API”进行比较。

您已经熟悉了API的概念。如果你想使用某些库或操作系统的特性，你将根据API进行编程。API由数据类型/结构、常量、函数等组成，您可以在代码中使用它们来访问外部组件的功能。

An ABI is very similar. Think of it as the compiled version of an API (or as an API on the machine-language level). When you write source code, you access the library through an API. Once the code is compiled, your application accesses the binary data in the library through the ABI. The ABI defines the structures and methods that your compiled application will use to access the external library (just like the API did), only on a lower level. Your API defines the order in which you pass arguments to a function. Your ABI defines the mechanics of how these arguments are passed (registers, stack, etc.). Your API defines which functions are part of your library. Your ABI defines how your code is stored inside the library file, so that any program using your library can locate the desired function and execute it.

ABIs are important when it comes to applications that use external libraries. Libraries are full of code and other resources, but your program has to know how to locate what it needs inside the library file. Your ABI defines how the contents of a library are stored inside the file, and your program uses the ABI to search through the file and find what it needs. If everything in your system conforms to the same ABI, then any program is able to work with any library file, no matter who created them. Linux and Windows use different ABIs, so a Windows program won't know how to access a library compiled for Linux.

有时，ABI更改是不可避免的。当这种情况发生时，任何使用该库的程序都将无法工作，除非它们被重新编译以使用新版本的库。如果ABI改变了，但API没有改变，那么新旧库版本有时被称为“源代码兼容”。这意味着，虽然为一个库版本编译的程序不能与另一个库版本一起工作，但为一个库版本编写的源代码如果重新编译，则可以与另一个库版本一起工作。

For this reason, developers tend to try to keep their ABI stable (to minimize disruption). Keeping an ABI stable means not changing function interfaces (return type and number, types, and order of arguments), definitions of data types or data structures, defined constants, etc. New functions and data types can be added, but existing ones must stay the same. If, for instance, your library uses 32-bit integers to indicate the offset of a function and you switch to 64-bit integers, then already-compiled code that uses that library will not be accessing that field (or any following it) correctly. Accessing data structure members gets converted into memory addresses and offsets during compilation and if the data structure changes, then these offsets will not point to what the code is expecting them to point to and the results are unpredictable at best.

除非您正在进行非常低级的系统设计工作，否则您不必显式地提供ABI。它也不是特定于语言的，因为(例如)C应用程序和Pascal应用程序在编译后可以使用相同的ABI。

Edit: Regarding your question about the chapters regarding the ELF file format in the SysV ABI docs: The reason this information is included is because the ELF format defines the interface between operating system and application. When you tell the OS to run a program, it expects the program to be formatted in a certain way and (for example) expects the first section of the binary to be an ELF header containing certain information at specific memory offsets. This is how the application communicates important information about itself to the operating system. If you build a program in a non-ELF binary format (such as a.out or PE), then an OS that expects ELF-formatted applications will not be able to interpret the binary file or run the application. This is one big reason why Windows apps cannot be run directly on a Linux machine (or vice versa) without being either re-compiled or run inside some type of emulation layer that can translate from one binary format to another.

IIRC, Windows目前使用可移植可执行文件(PE)格式。在维基百科页面的“外部链接”部分有关于PE格式的更多信息的链接。

Also, regarding your note about C++ name mangling: When locating a function in a library file, the function is typically looked up by name. C++ allows you to overload function names, so name alone is not sufficient to identify a function. C++ compilers have their own ways of dealing with this internally, called name mangling. An ABI can define a standard way of encoding the name of a function so that programs built with a different language or compiler can locate what they need. When you use extern "c" in a C++ program, you're instructing the compiler to use a standardized way of recording names that's understandable by other software.

术语ABI用于指代两个不同但相关的概念。

当谈到编译器时，它指的是用于从源级结构转换到二进制结构的规则。数据类型有多大?堆栈是如何工作的?如何将参数传递给函数?调用者和被调用者应该保存哪些寄存器?

当谈到库时，它指的是由编译库提供的二进制接口。这个接口是多种因素的结果，包括库的源代码、编译器使用的规则，以及在某些情况下从其他库中获得的定义。

对库的更改可以在不破坏API的情况下破坏ABI。例如，考虑具有如下接口的库。

void initfoo(FOO * foo)
int usefoo(FOO * foo, int bar)
void cleanupfoo(FOO * foo)

应用程序程序员编写的代码是

int dostuffwithfoo(int bar) {
  FOO foo;
  initfoo(&foo);
  int result = usefoo(&foo,bar)
  cleanupfoo(&foo);
  return result;
}

应用程序程序员并不关心FOO的大小或布局，但应用程序二进制文件最终会硬编码FOO的大小。如果标准库程序员在foo中添加了一个额外的字段，并且有人将新的标准库二进制文件与旧的应用程序二进制文件一起使用，那么标准库可能会进行越界内存访问。

OTOH，如果标准库的作者像这样设计他们的API。

FOO * newfoo(void)
int usefoo(FOO * foo, int bar)
void deletefoo((FOO * foo, int bar))

应用程序程序员编写的代码是

int dostuffwithfoo(int bar) {
  FOO * foo;
  foo = newfoo();
  int result = usefoo(foo,bar)
  deletefoo(foo);
  return result;
}

然后，应用程序二进制文件不需要知道任何关于FOO的结构，这些都可以隐藏在库中。你为此付出的代价是涉及到堆操作。

功能:一组影响编译器、程序集编写者、链接器和操作系统的契约。契约规定了函数如何布局，参数在哪里传递，参数如何传递，函数返回如何工作。这些元组通常特定于(处理器体系结构，操作系统)元组。

现有实体:参数布局、函数语义、寄存器分配。例如，ARM架构有许多ABI (APCS, EABI, GNU-EABI，更不用说一堆历史案例)-使用混合ABI会导致你的代码在跨边界调用时无法工作。

使用者:编译器、程序集编写器、操作系统、CPU特定架构。

谁需要这些细节?编译器，程序集编写者，代码生成(或对齐要求)的链接器，操作系统(中断处理，系统调用接口)。如果您进行汇编编程，那么您将遵循ABI!

c++的名称破坏是一个特殊的情况——它是一个以连接器和动态连接器为中心的问题——如果名称破坏没有标准化，那么动态链接将无法工作。从今以后，c++ ABI就这么叫了，c++ ABI。这不是链接器级别的问题，而是代码生成的问题。一旦你有了一个c++二进制文件，如果不从源代码重新编译，就不可能使它与另一个c++ ABI兼容(名称混乱，异常处理)。

ELF是一种用于加载器和动态链接器的文件格式。ELF是二进制代码和数据的容器格式，它指定了一段代码的ABI。我不认为ELF是严格意义上的ABI，因为PE可执行文件不是ABI。

所有的abi都是特定于指令集的。ARM ABI在MSP430或x86_64处理器上没有意义。

Windows有几个abi -例如，fastcall和stdcall是两个常用的abi。系统调用ABI又不同了。

我也试图理解ABI, JesperE的回答很有帮助。

从一个非常简单的角度来看，我们可以尝试通过考虑二进制兼容性来理解ABI。

KDE wiki将库定义为二进制兼容的，“如果动态链接到库的前版本的程序继续与库的新版本一起运行，而不需要重新编译”。有关动态链接的更多信息，请参阅静态链接与动态链接

现在，让我们试着看看一个库需要二进制兼容性的最基本方面(假设库没有源代码更改):

相同/向后兼容的指令集架构(处理器指令、寄存器文件结构、堆栈组织、内存访问类型，以及处理器可以直接访问的基本数据类型的大小、布局和对齐) 相同调用约定 同名混淆约定(如果Fortran程序需要调用一些c++库函数，这可能是需要的)。

当然，还有许多其他细节，但这主要是ABI所涵盖的内容。

更具体地回答你的问题，由以上，我们可以推断:

ABI功能:二进制兼容性 现有实体:现有程序/库/操作系统 消费者:库，操作系统

希望这能有所帮助!

应用二进制接口(ABI)

ABI -应用二进制接口是关于运行时两个二进制部分之间的机器码通信，如应用程序，库，操作系统…ABI描述了如何将对象保存在内存中，如何调用函数(调用约定)，如何修改…

API和ABI的一个很好的例子是iOS生态系统从v5开始使用Swift语言。

Application layer - When you create an application using different languages. For example you can create application using Swift and Objective-C[Mixing Swift and Objective-C] Application - OS layer - runtime - Swift Standard Library and Swift Run Time Library[About] are parts of OS and they should not be included into each bundle(e.g. app, framework). It is the same as like Objective-C uses. Available from iOS v12.2 Library layer - Module Stability case - compile time - you will be able to import a framework which was built with another version of Swift's compiler. It means that it is safety to create a closed-source(pre-build) binary which will be consumed by a different version of compiler( .swiftinterface is used with .swiftmodule[About]) and you will not get Module compiled with _ cannot be imported by the _ compiler //or Compiled module was created by a newer version of the compiler Library layer - Library Evolution case Compile time - if a dependency was changed, a client has not to be recompiled. Runtime - a system library or a dynamic framework can be hot-swapped by a new one.

[API vs ABI] [Swift模块稳定性和库稳定性]