Freebsd/as.h at master · lattera/freebsd. 4.3BSD - /usr/src/bin/as/as.h. Defined variables Defined struct's exp defined in line 307; used 83 times symtab defined in line 181; used 148 times Defined typedef's Defined macros.
Original-bsd/as.h at master · weiss/original-bsd. Freebsd/contrib/binutils/gas at master · freebsd/freebsd. GNU Binutils. The GNU Binutils are a collection of binary tools.
The main ones are: ld - the GNU linker. as - the GNU assembler. But they also include: addr2line - Converts addresses into filenames and line numbers. ar - A utility for creating, modifying and extracting from archives. c++filt - Filter to demangle encoded C++ symbols. dlltool - Creates files for building and using DLLs. gold - A new, faster, ELF only linker, still in beta test. gprof - Displays profiling information. nlmconv - Converts object code into an NLM. nm - Lists symbols from object files. objcopy - Copies and translates object files. objdump - Displays information from object files. ranlib - Generates an index to the contents of an archive. readelf - Displays information from any ELF format object file. size - Lists the section sizes of an object or archive file. strings - Lists printable strings from files. strip - Discards symbols. windmc - A Windows compatible message compiler. windres - A compiler for Windows resource files.
GNU Binutils. Index of /gnu/binutils. GAS. GAS is the GNU Assembler, that GCC relies upon.
Because GAS was invented to support a 32-bit unix compiler, it uses standard AT&T syntax, which resembles a lot the syntax for standard m68k assemblers, and is standard in the UNIX world. This syntax is neither worse, nor better than the Intel syntax. It's just different. X86 Assembly/GAS Syntax. General Information Examples in this article are created using the AT&T assembly syntax used in GNU AS.
The main advantage of using this syntax is its compatibility with the GCC inline assembly syntax. However, this is not the only syntax that is used to represent x86 operations. For example, NASM uses a different syntax to represent assembly mnemonics, operands and addressing modes, as do some High-Level Assemblers. The AT&T syntax is the standard on Unix-like systems but some assemblers use the Intel syntax, or can, like GAS itself, accept both.
GNU Assembler - Wikipedia. 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. Directives  Shell Programming (Linux) Assembler/Assembly Programming (Linux)