Commands Reference, Volume 1

as Command

Purpose

Reads and assembles a source file.

Syntax

as [ -a Mode ] [ -o ObjectFile ] [ -n Name ] [ -u ] [ -l [ ListFile ] ] [ -W | -w ] [ -x [ XCrossFile ] ] [ -s [ ListFile ] ] [ -m ModeName ] [ File ]

Description

The as command reads and assembles the named File (by convention, this file ends with a .s suffix). If you do not specify a File, the as command reads and assembles standard input. It stores its output, by default, in a file named a.out. The output is stored in the XCOFF file format.

All flags for the as command are optional.

Flags

-a Mode	Specifies the mode in which the as command operates. By default, the as command operates in 32-bit mode, but the mode can be explicitly set by using the flag -a32 for 32-bit mode operation or -a64 for 64-bit mode operation.
File	Specifies the source file. If no file is specified, the source code is taken from standard input.
-l[ListFile]	Produces an assembler listing. If you do not specify a file name, a default name is produced by replacing the suffix extension of the source file name with a .lst extension. By convention, the source file suffix is a .s. For example: sourcefile.xyz produces a default name of: sourcefile.lst If the source code is from standard input and the -l flag is used without specifying an assembler-listing file name, the listing file name is a.lst.
-m ModeName	Indicates the assembly mode. This flag has lower priority than the .machine pseudo-op. If this flag is not used and no .machine pseudo-op is present in the source program, the default assembly mode is used. The default assembly mode has the POWER family/PowerPC intersection as the target environment, but treats all POWER family/PowerPC incompatibility errors (including instructions outside the POWER family/PowerPC intersection and invalid form errors) as instructional warnings. If an assembly mode that is not valid is specified and no .machine pseudo-op is present in the source program, an error is reported and the default assembly mode is used for instruction validation in pass 1 of the assembler. If the -m flag is used, the ModeName variable can specify one of the following values: "" Explicitly specifies the default assembly mode that has the POWER family/PowerPC intersection as the target environment, but treats instructions outside the POWER family/PowerPC intersection and invalid form errors as instructional warnings. A space is required between -m and the null string argument (two double quotation marks). com Specifies the POWER family/PowerPC intersection mode. A source program can contain only instructions that are common to both POWER family and PowerPC; any other instruction causes an error. Any instruction with an invalid form causes errors, terminates the assembly process, and results in no object code being generated. Note Certain POWER family instructions are supported by the PowerPC 601 RISC Microprocessor in AIX 5.1 and earlier, but do not conform to the PowerPC architecture. These instructions cause errors when using the com assembly mode. any Specifies the indiscriminate mode. The assembler generates object code for any recognized instruction, regardless of architecture. This mode is used primarily for operating system development and for testing and debugging purposes. Note All POWER family and PowerPC incompatibility errors are ignored when using the any assembly mode, and no warnings are generated.
	ppc Specifies the PowerPC mode. A source program can contain only PowerPC instructions. Any other instruction causes an error. Notes: The PowerPC optional instructions are implemented in each PowerPC processor and do not belong to the ppc mode. These instructions generate an error if they appear in a source program that is assembled using the ppc assembly mode. Certain instructions conform to the PowerPC architecture, but are not supported by the PowerPC 601 RISC Microprocessor in AIX 5.1 and earlier. ppc64 Specifies the POWER-based 64-bit mode. A source program can contain 64-bit POWER-based instructions. pwr Specifies the POWER mode. A source program can contain only instructions for the POWER implementation of the POWER architecture.
	pwr2(pwrx) Specifies the POWER2 mode through AIX 5.1 only. A source program can contain only instructions for the POWER2 implementation of the POWER architecture in AIX 5.1 and earlier. pwr2 is the preferred value. The alternate assembly mode value pwrx means the same thing as pwr2. Note The POWER implementation instruction set is a subset of the POWER2 implementation instruction set for AIX 5.1 and earlier. 601 Specifies the PowerPC 601 RISC Microprocessor mode through AIX 5.1 only. A source program in AIX 5.1 and earlier can contain only instructions for the PowerPC 601 RISC Microprocessor. The PowerPC 601 RISC Microprocessor design was completed before the POWER-based platform for AIX 5.1 and earlier. Therefore, some PowerPC instructions may not be supported by the PowerPC 601 RISC Microprocessor in AIX 5.1 and earlier. Attention: It is recommended that the 601 assembly mode not be used for applications that are intended to be portable to future PowerPC systems. The com or ppc assembly mode should be used for such applications. The PowerPC 601 RISC Microprocessor in AIX 5.1 and earlier implements the POWER-based platform plus some POWER family instructions are not included in the POWER-based platform. This allows existing POWER applications to run with acceptable performance on POWER-based systems.
	603 Specifies the PowerPC 603 RISC Microprocessor mode through AIX 5.1 only. A source program can contain only instructions for the PowerPC 603 RISC Microprocessor in AIX 5.1 and earlier. 604 Specifies the PowerPC 604 RISC Microprocessormode. A source program can contain only instructions for the PowerPC 604 RISC Microprocessor. A35 Specifies the A35 mode. A source program can contain only instructions for the A35.
-n Name	Specifies the name that appears in the header of the assembler listing. By default, the header contains the name of the assembler source file.
-o ObjectFile	Writes the output of the assembly process to the specified file instead of to the a.out file.
-s[ListFile]	Indicates whether or not a mnemonics cross-reference for POWER family and PowerPC is included in the assembler listing. If this flag is omitted, no mnemonics cross-reference is produced. If this flag is used, the assembler listing will have POWER family mnemonics if the source contains PowerPC mnemonics, and will have PowerPC mnemonics if the source contains POWER family mnemonics. The mnemonics cross-reference is restricted to instructions that have different mnemonics in the POWER family and PowerPC, but that have the same op code, function, and input operand format. Because the -s flag is used to change the assembler-listing format, it implies the -l flag. If both option flags are used and different assembler-listing file names (specified by the ListFile variable) are given, the listing file name specified by the ListFile variable used with the -l flag is used. If an assembler-listing file name is not specified with either the -l or -s flag, a default assembler listing file name is produced by replacing the suffix extension of the source file name with a .lst extension.
-u	Accepts an undefined symbol as an extern so that an error message is not displayed. Otherwise, undefined symbols are flagged with error messages.
-W	Turns off all warning message reporting, including the instructional warning messages (the POWER family and PowerPC incompatibility warnings).
-w	Turns on warning message reporting, including reporting of instructional warning messages (the POWER family and PowerPC incompatibility warnings). Note When neither -W nor -w is specified, the instructional warnings are reported, but other warnings are suppressed.
-x[XCrossFile]	Produces cross reference output. If you do not specify a file name, a default name is produced by replacing the suffix extension of the source file name with an .xref extension. Conventionally, the suffix is a .s. For example: sourcefile.xyz produces a default name of: sourcefile.xref Note The assembler does not generate an object file when the -x flag is used.

Environment Variables

OBJECT_MODE

The assembler respects the setting of the OBJECT_MODE environment variable. If neither -a32 or -a64 is used, the environment is examined for this variable. If the value of the variable is anything other than the values listed in the following table, an error message is generated and the assembler exits with a non-zero return code. The implied behavior corresponding to the valid settings are as follows:

OBJECT_MODE = 32	Produce 32-bit object code. The default machine setting is com.
OBJECT_MODE = 64	Produce 64-bit object code (XCOFF64 files). The default machine setting is ppc64.
OBJECT_MODE = 32_64	Invalid.
OBJECT_MODE = anything else	Invalid.

Examples

To produce a listing file named file.lst and an object file named file.o, enter:
```
as -l -o file.o file.s
```
To produce an object file named file.o that will run on the 601 processor for AIX 5.1 and earlier and generate a cross reference for POWER family and PowerPC mnemonics in an assembler listing file named file.lst, enter:
```
as   -s   -m   601   -o   file.o   file.s
```
To produce an object file named file.o using the default assembly mode and an assembler listing file named xxx.lst with no mnemonics cross reference, enter:
```
as   -lxxx.lst   -o   file.o   file.s
```

Files

/usr/ccs/bin/as	Contains the as command
a.out	The default output file.

Related Information

The ld command, m4 command.

The Assembler Language Reference manual.