AS(1)							      General Commands Manual							     AS(1)

NAME

       as - Mac OS X Mach-O GNU-based assemblers

SYNOPSIS

       as [ option ...	] [ file ...  ]

DESCRIPTION

       The  as command translates assembly code in the named files to object code.  If no files are specified, as reads from stdin.  All undefined
       symbols in the assembly are treated as global.  The output of the assembly is left in the file a.out by default.

       The program /usr/bin/as is actually a driver that executes assemblers for specific target architectures.   If  no  target  architecture	is
       specified, it defaults to the architecture of the host it is running on.

OPTIONS

       -o name
	      Name the output file name instead of a.out.

       -arch arch_type
	      Specifies  the  target architecture, arch_type, of the assembler to be executed.	The target assemblers for each architecture are in
	      /usr/libexec/gcc/darwin/arch_type/as or /usr/local/libexec/gcc/darwin/arch_type/as.  There is only one assembler for an architecture
	      family.	If  the  specified target architecture is a machine-specific implementation, the assembler for that architecture family is
	      executed (e.g., /usr/libexec/gcc/darwin/ppc/as for -arch ppc604e).  See arch(3) for the currently known arch_types.

       -arch_multiple
	      Precede any displayed messages with a line stating the program name (as) and the architecture (from the -arch  arch_type	flag),	to
	      distinguish  which  architecture	the  error  messages refer to.	When the cc(1) driver program is run with multiple -arch flags, it
	      invokes as with the -arch_multiple option.

       -force_cpusubtype_ALL
	      By default, the assembler will produce the CPU subtype ALL for the object file it is assembling if it finds  no  implementation-spe-
	      cific instructions.  Also by default, the assembler will allow implementation-specific instructions and will combine the CPU subtype
	      for those specific implementations.  The combining of specific implementations is architecture-dependent;  if  some  combination	of
	      instructions  is not allowed, an error is generated.  With the optional -force_cpusubtype_ALL flag, all instructions are allowed and
	      the object file's CPU subtype will be the ALL subtype.  If the target architecture specified is  a  machine-specific  implementation
	      (e.g., -arch ppc603, -arch i486), the assembler will flag as errors instructions that are not supported on that architecture, and it
	      will produce an object file with the CPU subtype for that specific implementation (even if no  implementation-specific  instructions
	      are used).  The -force_cpusubtype_ALL flag is the default for all x86 and x86_64 architectures.

       -dynamic
	      Enables dynamic linking features.  This is the default.

       -static
	      Causes  the  assembler  to  treat  as an error any features for dynamic linking.	Also causes the .text directive to not include the
	      pure_instructions section attribute.

       --     Use stdin for the assembly source input.

       -n     Instructs the assembler not to assume that the assembly file starts with a .text directive.  Use this option when an output file	is
	      not to contain a (__TEXT,__text) section or this section is not to be first one in the output file.

       -f     Fast;  no need for the assembler preprocessor (``app'').	The assembler preprocessor can also be turned off by starting the assembly
	      file with "#NO_APP
".  This is intended for use by compilers which produce assembly code in a strict "clean" format that  specifies
	      exactly  where  whitespace can go.  The assembler preprocessor needs to be run on hand-written assembly files and/or files that have
	      been preprocessed by the C preprocessor cpp.  This is typically needed when assembler files are assembled through  the  use  of  the
	      cc(1)  command,  which automatically runs the C preprocessor on assembly source files.  The assembler preprocessor strips out excess
	      spaces, turns single-quoted characters into a decimal constants, and turns # <number> <filename> <level> into  .line  <number>;.file
	      <filename>   pairs.   When  the assembler preprocessor has been turned off by a "#NO_APP
" at the start of a file, it can be turned
	      back on and off again with pairs of "#APP
" and "#NO_APP
" at the beginnings of lines.	This is  used  by  the	compiler  to  wrap
	      assembly statements produced from asm() statements.

       -g     Produce debugging information for the symbolic debugger gdb(1) so that the assembly source can be debugged symbolically.	The debug-
	      ger depends on correct use of the C preprocessor's #include directive or the assembler's .include directive:  Any include file  that
	      produces	instructions  in the (__TEXT,__text) section must be included while a .text directive is in effect.  In other words, there
	      must be a .text directive before the include, and the .text directive must still be in effect at the end of the include file.   Oth-
	      erwise, the debugger will get confused when in that assembly file.

       -v     Display the version of the assembler (both the Mac OS X version and the GNU version it is based on).

       -V     Print the path and the command line of the assembler the assembler driver is using.

       -Idir  Add  the	directory  dir	to the list of directories to search for files included with the .include directive.  The default place to
	      search is the current directory.

       -W     Suppress warnings.

       -L     Save non-global defined labels beginning with an 'L'; these labels are normally discarded to save space in the resultant symbol  ta-
	      ble.  The compiler generates such temporary labels.

Assembler options for the PowerPC processors
       -static_branch_prediction_Y_bit
	      Treat  a single trailing '+' or '-' after a conditional PowerPC branch instruction as a static branch prediction that sets the Y-bit
	      in the opcode.  Pairs of trailing "++" or "--" always set the AT-bits. This is the default for Mac OS X.

       -static_branch_prediction_AT_bits
	      Treat a single trailing '+' or '-' after a conditional PowerPC branch instruction as a static branch prediction that  sets  the  AT-
	      bits in the opcode. Pairs of trailing "++" or "--" always set the AT-bits but with this option a warning is issued if this syntax is
	      used.  With this flag the assembler behaves like the IBM tools.

       -no_ppc601
	      Treat any PowerPC 601 instructions as an error.

FILES

       a.out	 output file

SEE ALSO

       The Mac OS X Assembler Reference in the Xcode documentation viewer: Perform a title search for "assembler" in Apple > Developer Tools  Ref-
       erence Library.
       The assembler source in the cctools module of the Darwin sources.
       cc(1), ld(1), nm(1), otool(1), arch(3), Mach-O(5)

Apple, Inc.							  April 24, 2007							     AS(1)