as
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-
specific 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\n". 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\n" at the start of
a file, it can be turned back on and off again with pairs of
"#APP\n" and "#NO_APP\n" 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
debugger 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.
Otherwise, 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
table. The compiler generates such temporary labels.
-q Use the clang(1) integrated assembler instead of the GNU based
system assembler. This is the default for the x86 and arm
architectures.
-Q Use the GNU based system assembler. Note that Apple's built-in
system assemblers are deprecated; programs that rely on these
asssemblers should move to the clang(1) integrated assembler
instead, using the -q flag.
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
cc(1), ld(1), nm(1), otool(1), arch(3), Mach-O(5)
Apple Inc. June 23, 2020 AS(1)