The GNU Assembler, commonly known as GAS (even though the program itself is as), is the assembler used by the GNU Project
GNU Project
The GNU Project is a free software, mass collaboration project, announced on September 27, 1983, by Richard Stallman at MIT. It initiated GNU operating system development in January, 1984...
The GNU Compiler Collection is a compiler system produced by the GNU Project supporting various programming languages. GCC is a key component of the GNU toolchain...
. It is used to assemble the GNU operating system and the Linux kernel
Linux kernel
The Linux kernel is an operating system kernel used by the Linux family of Unix-like operating systems. It is one of the most prominent examples of free and open source software....
, and various other software. It is a part of the GNU Binutils package.
In computing, an executable file causes a computer "to perform indicated tasks according to encoded instructions," as opposed to a data file that must be parsed by a program to be meaningful. These instructions are traditionally machine code instructions for a physical CPU...
Unix is a multitasking, multi-user computer operating system originally developed in 1969 by a group of AT&T employees at Bell Labs, including Ken Thompson, Dennis Ritchie, Brian Kernighan, Douglas McIlroy, and Joe Ossanna...
In computing, cross-platform, or multi-platform, is an attribute conferred to computer software or computing methods and concepts that are implemented and inter-operate on multiple computer platforms...
In computer science and engineering, computer architecture is the practical art of selecting and interconnecting hardware components to create computers that meet functional, performance and cost goals and the formal modelling of those systems....
Free software, software libre or libre software is software that can be used, studied, and modified without restriction, and which can be copied and redistributed in modified or unmodified form either without restriction, or with restrictions that only ensure that further recipients can also do...
.
General syntax
GAS supports a general syntax that works for all of the supported architectures. The general syntax includes assembler directives and a method for commenting.
In computer programming, the term directive is applied in a variety of ways that are similar to the term command. It is also used to describe some programming language constructs ....
(also known as pseudo ops), which are keywords beginning with a period that behave similarly to preprocessor directives in the C programming language
C (programming language)
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
. While most of the available assembler directives are valid regardless of the target architecture, some directives are machine dependent.
In computing, a newline, also known as a line break or end-of-line marker, is a special character or sequence of characters signifying the end of a line of text. The name comes from the fact that the next character after the newline will appear on a new line—that is, on the next line below the...
character. Example:
comment
popl %edx # comment
Criticism
One source of criticism was that on the x86 and x86-64
X86-64
x86-64 is an extension of the x86 instruction set. It supports vastly larger virtual and physical address spaces than are possible on x86, thereby allowing programmers to conveniently work with much larger data sets. x86-64 also provides 64-bit general purpose registers and numerous other...
architecture it uses the AT&T assembler syntax, rather than the Intel syntax used in many other assemblers; however, in versions from 2.10 support for the Intel syntax via the .intel_syntax directive has been added.
C is a general-purpose computer programming language developed between 1969 and 1973 by Dennis Ritchie at the Bell Telephone Laboratories for use with the Unix operating system....
In computer programming, the inline assembler is a feature of some compilers that allows very low level code written in assembly to be embedded in a high level language like C or Ada...
in Intel syntax:
__asm__ __volatile__(".intel_syntax noprefix\n\t"
"pop edx\n\t"
"mov eax,edx\n\t"
".att_syntax prefix\n\t"
: /* no outputs */
: "d" (save_var), "a" (temp_var) /* inputs */
: "eax", "edx" /* clobber list */);
The GNU toolchain is a blanket term for a collection of programming tools produced by the GNU Project. These tools form a toolchain used for developing applications and operating systems....
International Business Machines Corporation or IBM is an American multinational technology and consulting corporation headquartered in Armonk, New York, United States. IBM manufactures and sells computer hardware and software, and it offers infrastructure, hosting and consulting services in areas...
The source of this article is wikipedia, the free encyclopedia. The text of this article is licensed under the GFDL.
