This is as.info, produced by makeinfo version 4.0 from as.texinfo. START-INFO-DIR-ENTRY * As: (as). The GNU assembler. END-INFO-DIR-ENTRY This file documents the GNU Assembler "as". Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001 Free Software Foundation, Inc. Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.1 or any later version published by the Free Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-Cover Texts. A copy of the license is included in the section entitled "GNU Free Documentation License".  File: as.info, Node: Integers, Next: Bignums, Up: Numbers Integers ........ A binary integer is `0b' or `0B' followed by zero or more of the binary digits `01'. An octal integer is `0' followed by zero or more of the octal digits (`01234567'). A decimal integer starts with a non-zero digit followed by zero or more digits (`0123456789'). A hexadecimal integer is `0x' or `0X' followed by one or more hexadecimal digits chosen from `0123456789abcdefABCDEF'. Integers have the usual values. To denote a negative integer, use the prefix operator `-' discussed under expressions (*note Prefix Operators: Prefix Ops.).  File: as.info, Node: Bignums, Next: Flonums, Prev: Integers, Up: Numbers Bignums ....... A "bignum" has the same syntax and semantics as an integer except that the number (or its negative) takes more than 32 bits to represent in binary. The distinction is made because in some places integers are permitted while bignums are not.  File: as.info, Node: Flonums, Prev: Bignums, Up: Numbers Flonums ....... A "flonum" represents a floating point number. The translation is indirect: a decimal floating point number from the text is converted by `as' to a generic binary floating point number of more than sufficient precision. This generic floating point number is converted to a particular computer's floating point format (or formats) by a portion of `as' specialized to that computer. A flonum is written by writing (in order) * The digit `0'. (`0' is optional on the HPPA.) * A letter, to tell `as' the rest of the number is a flonum. `e' is recommended. Case is not important. On the H8/300, H8/500, Hitachi SH, and AMD 29K architectures, the letter must be one of the letters `DFPRSX' (in upper or lower case). On the ARC, the letter must be one of the letters `DFRS' (in upper or lower case). On the Intel 960 architecture, the letter must be one of the letters `DFT' (in upper or lower case). On the HPPA architecture, the letter must be `E' (upper case only). * An optional sign: either `+' or `-'. * An optional "integer part": zero or more decimal digits. * An optional "fractional part": `.' followed by zero or more decimal digits. * An optional exponent, consisting of: * An `E' or `e'. * Optional sign: either `+' or `-'. * One or more decimal digits. At least one of the integer part or the fractional part must be present. The floating point number has the usual base-10 value. `as' does all processing using integers. Flonums are computed independently of any floating point hardware in the computer running `as'.  File: as.info, Node: Sections, Next: Symbols, Prev: Syntax, Up: Top Sections and Relocation *********************** * Menu: * Secs Background:: Background * Ld Sections:: Linker Sections * As Sections:: Assembler Internal Sections * Sub-Sections:: Sub-Sections * bss:: bss Section  File: as.info, Node: Secs Background, Next: Ld Sections, Up: Sections Background ========== Roughly, a section is a range of addresses, with no gaps; all data "in" those addresses is treated the same for some particular purpose. For example there may be a "read only" section. The linker `ld' reads many object files (partial programs) and combines their contents to form a runnable program. When `as' emits an object file, the partial program is assumed to start at address 0. `ld' assigns the final addresses for the partial program, so that different partial programs do not overlap. This is actually an oversimplification, but it suffices to explain how `as' uses sections. `ld' moves blocks of bytes of your program to their run-time addresses. These blocks slide to their run-time addresses as rigid units; their length does not change and neither does the order of bytes within them. Such a rigid unit is called a _section_. Assigning run-time addresses to sections is called "relocation". It includes the task of adjusting mentions of object-file addresses so they refer to the proper run-time addresses. For the H8/300 and H8/500, and for the Hitachi SH, `as' pads sections if needed to ensure they end on a word (sixteen bit) boundary. An object file written by `as' has at least three sections, any of which may be empty. These are named "text", "data" and "bss" sections. When it generates COFF output, `as' can also generate whatever other named sections you specify using the `.section' directive (*note `.section': Section.). If you do not use any directives that place output in the `.text' or `.data' sections, these sections still exist, but are empty. When `as' generates SOM or ELF output for the HPPA, `as' can also generate whatever other named sections you specify using the `.space' and `.subspace' directives. See `HP9000 Series 800 Assembly Language Reference Manual' (HP 92432-90001) for details on the `.space' and `.subspace' assembler directives. Additionally, `as' uses different names for the standard text, data, and bss sections when generating SOM output. Program text is placed into the `$CODE$' section, data into `$DATA$', and BSS into `$BSS$'. Within the object file, the text section starts at address `0', the data section follows, and the bss section follows the data section. When generating either SOM or ELF output files on the HPPA, the text section starts at address `0', the data section at address `0x4000000', and the bss section follows the data section. To let `ld' know which data changes when the sections are relocated, and how to change that data, `as' also writes to the object file details of the relocation needed. To perform relocation `ld' must know, each time an address in the object file is mentioned: * Where in the object file is the beginning of this reference to an address? * How long (in bytes) is this reference? * Which section does the address refer to? What is the numeric value of (ADDRESS) - (START-ADDRESS OF SECTION)? * Is the reference to an address "Program-Counter relative"? In fact, every address `as' ever uses is expressed as (SECTION) + (OFFSET INTO SECTION) Further, most expressions `as' computes have this section-relative nature. (For some object formats, such as SOM for the HPPA, some expressions are symbol-relative instead.) In this manual we use the notation {SECNAME N} to mean "offset N into section SECNAME." Apart from text, data and bss sections you need to know about the "absolute" section. When `ld' mixes partial programs, addresses in the absolute section remain unchanged. For example, address `{absolute 0}' is "relocated" to run-time address 0 by `ld'. Although the linker never arranges two partial programs' data sections with overlapping addresses after linking, _by definition_ their absolute sections must overlap. Address `{absolute 239}' in one part of a program is always the same address when the program is running as address `{absolute 239}' in any other part of the program. The idea of sections is extended to the "undefined" section. Any address whose section is unknown at assembly time is by definition rendered {undefined U}--where U is filled in later. Since numbers are always defined, the only way to generate an undefined address is to mention an undefined symbol. A reference to a named common block would be such a symbol: its value is unknown at assembly time so it has section _undefined_. By analogy the word _section_ is used to describe groups of sections in the linked program. `ld' puts all partial programs' text sections in contiguous addresses in the linked program. It is customary to refer to the _text section_ of a program, meaning all the addresses of all partial programs' text sections. Likewise for data and bss sections. Some sections are manipulated by `ld'; others are invented for use of `as' and have no meaning except during assembly.  File: as.info, Node: Ld Sections, Next: As Sections, Prev: Secs Background, Up: Sections Linker Sections =============== `ld' deals with just four kinds of sections, summarized below. *named sections* *text section* *data section* These sections hold your program. `as' and `ld' treat them as separate but equal sections. Anything you can say of one section is true another. When the program is running, however, it is customary for the text section to be unalterable. The text section is often shared among processes: it contains instructions, constants and the like. The data section of a running program is usually alterable: for example, C variables would be stored in the data section. *bss section* This section contains zeroed bytes when your program begins running. It is used to hold uninitialized variables or common storage. The length of each partial program's bss section is important, but because it starts out containing zeroed bytes there is no need to store explicit zero bytes in the object file. The bss section was invented to eliminate those explicit zeros from object files. *absolute section* Address 0 of this section is always "relocated" to runtime address 0. This is useful if you want to refer to an address that `ld' must not change when relocating. In this sense we speak of absolute addresses being "unrelocatable": they do not change during relocation. *undefined section* This "section" is a catch-all for address references to objects not in the preceding sections. An idealized example of three relocatable sections follows. The example uses the traditional section names `.text' and `.data'. Memory addresses are on the horizontal axis. +-----+----+--+ partial program # 1: |ttttt|dddd|00| +-----+----+--+ text data bss seg. seg. seg. +---+---+---+ partial program # 2: |TTT|DDD|000| +---+---+---+ +--+---+-----+--+----+---+-----+~~ linked program: | |TTT|ttttt| |dddd|DDD|00000| +--+---+-----+--+----+---+-----+~~ addresses: 0 ...  File: as.info, Node: As Sections, Next: Sub-Sections, Prev: Ld Sections, Up: Sections Assembler Internal Sections =========================== These sections are meant only for the internal use of `as'. They have no meaning at run-time. You do not really need to know about these sections for most purposes; but they can be mentioned in `as' warning messages, so it might be helpful to have an idea of their meanings to `as'. These sections are used to permit the value of every expression in your assembly language program to be a section-relative address. ASSEMBLER-INTERNAL-LOGIC-ERROR! An internal assembler logic error has been found. This means there is a bug in the assembler. expr section The assembler stores complex expression internally as combinations of symbols. When it needs to represent an expression as a symbol, it puts it in the expr section.  File: as.info, Node: Sub-Sections, Next: bss, Prev: As Sections, Up: Sections Sub-Sections ============ Assembled bytes conventionally fall into two sections: text and data. You may have separate groups of data in named sections that you want to end up near to each other in the object file, even though they are not contiguous in the assembler source. `as' allows you to use "subsections" for this purpose. Within each section, there can be numbered subsections with values from 0 to 8192. Objects assembled into the same subsection go into the object file together with other objects in the same subsection. For example, a compiler might want to store constants in the text section, but might not want to have them interspersed with the program being assembled. In this case, the compiler could issue a `.text 0' before each section of code being output, and a `.text 1' before each group of constants being output. Subsections are optional. If you do not use subsections, everything goes in subsection number zero. Each subsection is zero-padded up to a multiple of four bytes. (Subsections may be padded a different amount on different flavors of `as'.) Subsections appear in your object file in numeric order, lowest numbered to highest. (All this to be compatible with other people's assemblers.) The object file contains no representation of subsections; `ld' and other programs that manipulate object files see no trace of them. They just see all your text subsections as a text section, and all your data subsections as a data section. To specify which subsection you want subsequent statements assembled into, use a numeric argument to specify it, in a `.text EXPRESSION' or a `.data EXPRESSION' statement. When generating COFF output, you can also use an extra subsection argument with arbitrary named sections: `.section NAME, EXPRESSION'. EXPRESSION should be an absolute expression. (*Note Expressions::.) If you just say `.text' then `.text 0' is assumed. Likewise `.data' means `.data 0'. Assembly begins in `text 0'. For instance: .text 0 # The default subsection is text 0 anyway. .ascii "This lives in the first text subsection. *" .text 1 .ascii "But this lives in the second text subsection." .data 0 .ascii "This lives in the data section," .ascii "in the first data subsection." .text 0 .ascii "This lives in the first text section," .ascii "immediately following the asterisk (*)." Each section has a "location counter" incremented by one for every byte assembled into that section. Because subsections are merely a convenience restricted to `as' there is no concept of a subsection location counter. There is no way to directly manipulate a location counter--but the `.align' directive changes it, and any label definition captures its current value. The location counter of the section where statements are being assembled is said to be the "active" location counter.  File: as.info, Node: bss, Prev: Sub-Sections, Up: Sections bss Section =========== The bss section is used for local common variable storage. You may allocate address space in the bss section, but you may not dictate data to load into it before your program executes. When your program starts running, all the contents of the bss section are zeroed bytes. The `.lcomm' pseudo-op defines a symbol in the bss section; see *Note `.lcomm': Lcomm. The `.comm' pseudo-op may be used to declare a common symbol, which is another form of uninitialized symbol; see *Note `.comm': Comm. When assembling for a target which supports multiple sections, such as ELF or COFF, you may switch into the `.bss' section and define symbols as usual; see *Note `.section': Section. You may only assemble zero values into the section. Typically the section will only contain symbol definitions and `.skip' directives (*note `.skip': Skip.).  File: as.info, Node: Symbols, Next: Expressions, Prev: Sections, Up: Top Symbols ******* Symbols are a central concept: the programmer uses symbols to name things, the linker uses symbols to link, and the debugger uses symbols to debug. _Warning:_ `as' does not place symbols in the object file in the same order they were declared. This may break some debuggers. * Menu: * Labels:: Labels * Setting Symbols:: Giving Symbols Other Values * Symbol Names:: Symbol Names * Dot:: The Special Dot Symbol * Symbol Attributes:: Symbol Attributes  File: as.info, Node: Labels, Next: Setting Symbols, Up: Symbols Labels ====== A "label" is written as a symbol immediately followed by a colon `:'. The symbol then represents the current value of the active location counter, and is, for example, a suitable instruction operand. You are warned if you use the same symbol to represent two different locations: the first definition overrides any other definitions. On the HPPA, the usual form for a label need not be immediately followed by a colon, but instead must start in column zero. Only one label may be defined on a single line. To work around this, the HPPA version of `as' also provides a special directive `.label' for defining labels more flexibly.  File: as.info, Node: Setting Symbols, Next: Symbol Names, Prev: Labels, Up: Symbols Giving Symbols Other Values =========================== A symbol can be given an arbitrary value by writing a symbol, followed by an equals sign `=', followed by an expression (*note Expressions::). This is equivalent to using the `.set' directive. *Note `.set': Set.  File: as.info, Node: Symbol Names, Next: Dot, Prev: Setting Symbols, Up: Symbols Symbol Names ============ Symbol names begin with a letter or with one of `._'. On most machines, you can also use `$' in symbol names; exceptions are noted in *Note Machine Dependencies::. That character may be followed by any string of digits, letters, dollar signs (unless otherwise noted in *Note Machine Dependencies::), and underscores. For the AMD 29K family, `?' is also allowed in the body of a symbol name, though not at its beginning. Case of letters is significant: `foo' is a different symbol name than `Foo'. Each symbol has exactly one name. Each name in an assembly language program refers to exactly one symbol. You may use that symbol name any number of times in a program. Local Symbol Names ------------------ Local symbols help compilers and programmers use names temporarily. There are ten local symbol names, which are re-used throughout the program. You may refer to them using the names `0' `1' ... `9'. To define a local symbol, write a label of the form `N:' (where N represents any digit). To refer to the most recent previous definition of that symbol write `Nb', using the same digit as when you defined the label. To refer to the next definition of a local label, write `Nf'--where N gives you a choice of 10 forward references. The `b' stands for "backwards" and the `f' stands for "forwards". Local symbols are not emitted by the current GNU C compiler. There is no restriction on how you can use these labels, but remember that at any point in the assembly you can refer to at most 10 prior local labels and to at most 10 forward local labels. Local symbol names are only a notation device. They are immediately transformed into more conventional symbol names before the assembler uses them. The symbol names stored in the symbol table, appearing in error messages and optionally emitted to the object file have these parts: `L' All local labels begin with `L'. Normally both `as' and `ld' forget symbols that start with `L'. These labels are used for symbols you are never intended to see. If you use the `-L' option then `as' retains these symbols in the object file. If you also instruct `ld' to retain these symbols, you may use them in debugging. `DIGIT' If the label is written `0:' then the digit is `0'. If the label is written `1:' then the digit is `1'. And so on up through `9:'. `C-A' This unusual character is included so you do not accidentally invent a symbol of the same name. The character has ASCII value `\001'. `_ordinal number_' This is a serial number to keep the labels distinct. The first `0:' gets the number `1'; The 15th `0:' gets the number `15'; _etc._. Likewise for the other labels `1:' through `9:'. For instance, the first `1:' is named `L1C-A1', the 44th `3:' is named `L3C-A44'.  File: as.info, Node: Dot, Next: Symbol Attributes, Prev: Symbol Names, Up: Symbols The Special Dot Symbol ====================== The special symbol `.' refers to the current address that `as' is assembling into. Thus, the expression `melvin: .long .' defines `melvin' to contain its own address. Assigning a value to `.' is treated the same as a `.org' directive. Thus, the expression `.=.+4' is the same as saying `.space 4'.  File: as.info, Node: Symbol Attributes, Prev: Dot, Up: Symbols Symbol Attributes ================= Every symbol has, as well as its name, the attributes "Value" and "Type". Depending on output format, symbols can also have auxiliary attributes. If you use a symbol without defining it, `as' assumes zero for all these attributes, and probably won't warn you. This makes the symbol an externally defined symbol, which is generally what you would want. * Menu: * Symbol Value:: Value * Symbol Type:: Type * a.out Symbols:: Symbol Attributes: `a.out' * COFF Symbols:: Symbol Attributes for COFF * SOM Symbols:: Symbol Attributes for SOM  File: as.info, Node: Symbol Value, Next: Symbol Type, Up: Symbol Attributes Value ----- The value of a symbol is (usually) 32 bits. For a symbol which labels a location in the text, data, bss or absolute sections the value is the number of addresses from the start of that section to the label. Naturally for text, data and bss sections the value of a symbol changes as `ld' changes section base addresses during linking. Absolute symbols' values do not change during linking: that is why they are called absolute. The value of an undefined symbol is treated in a special way. If it is 0 then the symbol is not defined in this assembler source file, and `ld' tries to determine its value from other files linked into the same program. You make this kind of symbol simply by mentioning a symbol name without defining it. A non-zero value represents a `.comm' common declaration. The value is how much common storage to reserve, in bytes (addresses). The symbol refers to the first address of the allocated storage.  File: as.info, Node: Symbol Type, Next: a.out Symbols, Prev: Symbol Value, Up: Symbol Attributes Type ---- The type attribute of a symbol contains relocation (section) information, any flag settings indicating that a symbol is external, and (optionally), other information for linkers and debuggers. The exact format depends on the object-code output format in use.  File: as.info, Node: a.out Symbols, Next: COFF Symbols, Prev: Symbol Type, Up: Symbol Attributes Symbol Attributes: `a.out' -------------------------- * Menu: * Symbol Desc:: Descriptor * Symbol Other:: Other  File: as.info, Node: Symbol Desc, Next: Symbol Other, Up: a.out Symbols Descriptor .......... This is an arbitrary 16-bit value. You may establish a symbol's descriptor value by using a `.desc' statement (*note `.desc': Desc.). A descriptor value means nothing to `as'.  File: as.info, Node: Symbol Other, Prev: Symbol Desc, Up: a.out Symbols Other ..... This is an arbitrary 8-bit value. It means nothing to `as'.  File: as.info, Node: COFF Symbols, Next: SOM Symbols, Prev: a.out Symbols, Up: Symbol Attributes Symbol Attributes for COFF -------------------------- The COFF format supports a multitude of auxiliary symbol attributes; like the primary symbol attributes, they are set between `.def' and `.endef' directives. Primary Attributes .................. The symbol name is set with `.def'; the value and type, respectively, with `.val' and `.type'. Auxiliary Attributes .................... The `as' directives `.dim', `.line', `.scl', `.size', and `.tag' can generate auxiliary symbol table information for COFF.  File: as.info, Node: SOM Symbols, Prev: COFF Symbols, Up: Symbol Attributes Symbol Attributes for SOM ------------------------- The SOM format for the HPPA supports a multitude of symbol attributes set with the `.EXPORT' and `.IMPORT' directives. The attributes are described in `HP9000 Series 800 Assembly Language Reference Manual' (HP 92432-90001) under the `IMPORT' and `EXPORT' assembler directive documentation.  File: as.info, Node: Expressions, Next: Pseudo Ops, Prev: Symbols, Up: Top Expressions *********** An "expression" specifies an address or numeric value. Whitespace may precede and/or follow an expression. The result of an expression must be an absolute number, or else an offset into a particular section. If an expression is not absolute, and there is not enough information when `as' sees the expression to know its section, a second pass over the source program might be necessary to interpret the expression--but the second pass is currently not implemented. `as' aborts with an error message in this situation. * Menu: * Empty Exprs:: Empty Expressions * Integer Exprs:: Integer Expressions  File: as.info, Node: Empty Exprs, Next: Integer Exprs, Up: Expressions Empty Expressions ================= An empty expression has no value: it is just whitespace or null. Wherever an absolute expression is required, you may omit the expression, and `as' assumes a value of (absolute) 0. This is compatible with other assemblers.  File: as.info, Node: Integer Exprs, Prev: Empty Exprs, Up: Expressions Integer Expressions =================== An "integer expression" is one or more _arguments_ delimited by _operators_. * Menu: * Arguments:: Arguments * Operators:: Operators * Prefix Ops:: Prefix Operators * Infix Ops:: Infix Operators  File: as.info, Node: Arguments, Next: Operators, Up: Integer Exprs Arguments --------- "Arguments" are symbols, numbers or subexpressions. In other contexts arguments are sometimes called "arithmetic operands". In this manual, to avoid confusing them with the "instruction operands" of the machine language, we use the term "argument" to refer to parts of expressions only, reserving the word "operand" to refer only to machine instruction operands. Symbols are evaluated to yield {SECTION NNN} where SECTION is one of text, data, bss, absolute, or undefined. NNN is a signed, 2's complement 32 bit integer. Numbers are usually integers. A number can be a flonum or bignum. In this case, you are warned that only the low order 32 bits are used, and `as' pretends these 32 bits are an integer. You may write integer-manipulating instructions that act on exotic constants, compatible with other assemblers. Subexpressions are a left parenthesis `(' followed by an integer expression, followed by a right parenthesis `)'; or a prefix operator followed by an argument.  File: as.info, Node: Operators, Next: Prefix Ops, Prev: Arguments, Up: Integer Exprs Operators --------- "Operators" are arithmetic functions, like `+' or `%'. Prefix operators are followed by an argument. Infix operators appear between their arguments. Operators may be preceded and/or followed by whitespace.  File: as.info, Node: Prefix Ops, Next: Infix Ops, Prev: Operators, Up: Integer Exprs Prefix Operator --------------- `as' has the following "prefix operators". They each take one argument, which must be absolute. `-' "Negation". Two's complement negation. `~' "Complementation". Bitwise not.  File: as.info, Node: Infix Ops, Prev: Prefix Ops, Up: Integer Exprs Infix Operators --------------- "Infix operators" take two arguments, one on either side. Operators have precedence, but operations with equal precedence are performed left to right. Apart from `+' or `-', both arguments must be absolute, and the result is absolute. 1. Highest Precedence `*' "Multiplication". `/' "Division". Truncation is the same as the C operator `/' `%' "Remainder". `<' `<<' "Shift Left". Same as the C operator `<<'. `>' `>>' "Shift Right". Same as the C operator `>>'. 2. Intermediate precedence `|' "Bitwise Inclusive Or". `&' "Bitwise And". `^' "Bitwise Exclusive Or". `!' "Bitwise Or Not". 3. Low Precedence `+' "Addition". If either argument is absolute, the result has the section of the other argument. You may not add together arguments from different sections. `-' "Subtraction". If the right argument is absolute, the result has the section of the left argument. If both arguments are in the same section, the result is absolute. You may not subtract arguments from different sections. `==' "Is Equal To" `<>' "Is Not Equal To" `<' "Is Less Than" `>' "Is Greater Than" `>=' "Is Greater Than Or Equal To" `<=' "Is Less Than Or Equal To" The comparison operators can be used as infix operators. A true results has a value of -1 whereas a false result has a value of 0. Note, these operators perform signed comparisons. 4. Lowest Precedence `&&' "Logical And". `||' "Logical Or". These two logical operations can be used to combine the results of sub expressions. Note, unlike the comparison operators a true result returns a value of 1 but a false results does still return 0. Also note that the logical or operator has a slightly lower precedence than logical and. In short, it's only meaningful to add or subtract the _offsets_ in an address; you can only have a defined section in one of the two arguments.  File: as.info, Node: Pseudo Ops, Next: Machine Dependencies, Prev: Expressions, Up: Top Assembler Directives ******************** All assembler directives have names that begin with a period (`.'). The rest of the name is letters, usually in lower case. This chapter discusses directives that are available regardless of the target machine configuration for the GNU assembler. Some machine configurations provide additional directives. *Note Machine Dependencies::. * Menu: * Abort:: `.abort' * ABORT:: `.ABORT' * Align:: `.align ABS-EXPR , ABS-EXPR' * Ascii:: `.ascii "STRING"'... * Asciz:: `.asciz "STRING"'... * Balign:: `.balign ABS-EXPR , ABS-EXPR' * Byte:: `.byte EXPRESSIONS' * Comm:: `.comm SYMBOL , LENGTH ' * Data:: `.data SUBSECTION' * Def:: `.def NAME' * Desc:: `.desc SYMBOL, ABS-EXPRESSION' * Dim:: `.dim' * Double:: `.double FLONUMS' * Eject:: `.eject' * Else:: `.else' * Elseif:: `.elseif' * End:: `.end' * Endef:: `.endef' * Endfunc:: `.endfunc' * Endif:: `.endif' * Equ:: `.equ SYMBOL, EXPRESSION' * Equiv:: `.equiv SYMBOL, EXPRESSION' * Err:: `.err' * Exitm:: `.exitm' * Extern:: `.extern' * Fail:: `.fail' * File:: `.file STRING' * Fill:: `.fill REPEAT , SIZE , VALUE' * Float:: `.float FLONUMS' * Func:: `.func' * Global:: `.global SYMBOL', `.globl SYMBOL' * Hidden:: `.hidden NAMES' * hword:: `.hword EXPRESSIONS' * Ident:: `.ident' * If:: `.if ABSOLUTE EXPRESSION' * Include:: `.include "FILE"' * Int:: `.int EXPRESSIONS' * Internal:: `.internal NAMES' * Irp:: `.irp SYMBOL,VALUES'... * Irpc:: `.irpc SYMBOL,VALUES'... * Lcomm:: `.lcomm SYMBOL , LENGTH' * Lflags:: `.lflags' * Line:: `.line LINE-NUMBER' * Ln:: `.ln LINE-NUMBER' * Linkonce:: `.linkonce [TYPE]' * List:: `.list' * Long:: `.long EXPRESSIONS' * Macro:: `.macro NAME ARGS'... * MRI:: `.mri VAL' * Nolist:: `.nolist' * Octa:: `.octa BIGNUMS' * Org:: `.org NEW-LC , FILL' * P2align:: `.p2align ABS-EXPR , ABS-EXPR' * PopSection:: `.popsection' * Previous:: `.previous' * Print:: `.print STRING' * Protected:: `.protected NAMES' * Psize:: `.psize LINES, COLUMNS' * Purgem:: `.purgem NAME' * PushSection:: `.pushsection NAME' * Quad:: `.quad BIGNUMS' * Rept:: `.rept COUNT' * Sbttl:: `.sbttl "SUBHEADING"' * Scl:: `.scl CLASS' * Section:: `.section NAME, SUBSECTION' * Set:: `.set SYMBOL, EXPRESSION' * Short:: `.short EXPRESSIONS' * Single:: `.single FLONUMS' * Size:: `.size [NAME , EXPRESSION]' * Skip:: `.skip SIZE , FILL' * Sleb128:: `.sleb128 EXPRESSIONS' * Space:: `.space SIZE , FILL' * Stab:: `.stabd, .stabn, .stabs' * String:: `.string "STR"' * Struct:: `.struct EXPRESSION' * SubSection:: `.subsection' * Symver:: `.symver NAME,NAME2@NODENAME' * Tag:: `.tag STRUCTNAME' * Text:: `.text SUBSECTION' * Title:: `.title "HEADING"' * Type:: `.type ' * Uleb128:: `.uleb128 EXPRESSIONS' * Val:: `.val ADDR' * Version:: `.version "STRING"' * VTableEntry:: `.vtable_entry TABLE, OFFSET' * VTableInherit:: `.vtable_inherit CHILD, PARENT' * Weak:: `.weak NAMES' * Word:: `.word EXPRESSIONS' * Deprecated:: Deprecated Directives  File: as.info, Node: Abort, Next: ABORT, Up: Pseudo Ops `.abort' ======== This directive stops the assembly immediately. It is for compatibility with other assemblers. The original idea was that the assembly language source would be piped into the assembler. If the sender of the source quit, it could use this directive tells `as' to quit also. One day `.abort' will not be supported.  File: as.info, Node: ABORT, Next: Align, Prev: Abort, Up: Pseudo Ops `.ABORT' ======== When producing COFF output, `as' accepts this directive as a synonym for `.abort'. When producing `b.out' output, `as' accepts this directive, but ignores it.  File: as.info, Node: Align, Next: Ascii, Prev: ABORT, Up: Pseudo Ops `.align ABS-EXPR, ABS-EXPR, ABS-EXPR' ===================================== Pad the location counter (in the current subsection) to a particular storage boundary. The first expression (which must be absolute) is the alignment required, as described below. The second expression (also absolute) gives the fill value to be stored in the padding bytes. It (and the comma) may be omitted. If it is omitted, the padding bytes are normally zero. However, on some systems, if the section is marked as containing code and the fill value is omitted, the space is filled with no-op instructions. The third expression is also absolute, and is also optional. If it is present, it is the maximum number of bytes that should be skipped by this alignment directive. If doing the alignment would require skipping more bytes than the specified maximum, then the alignment is not done at all. You can omit the fill value (the second argument) entirely by simply using two commas after the required alignment; this can be useful if you want the alignment to be filled with no-op instructions when appropriate. The way the required alignment is specified varies from system to system. For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF format, the first expression is the alignment request in bytes. For example `.align 8' advances the location counter until it is a multiple of 8. If the location counter is already a multiple of 8, no change is needed. For other systems, including the i386 using a.out format, and the arm and strongarm, it is the number of low-order zero bits the location counter must have after advancement. For example `.align 3' advances the location counter until it a multiple of 8. If the location counter is already a multiple of 8, no change is needed. This inconsistency is due to the different behaviors of the various native assemblers for these systems which GAS must emulate. GAS also provides `.balign' and `.p2align' directives, described later, which have a consistent behavior across all architectures (but are specific to GAS).  File: as.info, Node: Ascii, Next: Asciz, Prev: Align, Up: Pseudo Ops `.ascii "STRING"'... ==================== `.ascii' expects zero or more string literals (*note Strings::) separated by commas. It assembles each string (with no automatic trailing zero byte) into consecutive addresses.  File: as.info, Node: Asciz, Next: Balign, Prev: Ascii, Up: Pseudo Ops `.asciz "STRING"'... ==================== `.asciz' is just like `.ascii', but each string is followed by a zero byte. The "z" in `.asciz' stands for "zero".  File: as.info, Node: Balign, Next: Byte, Prev: Asciz, Up: Pseudo Ops `.balign[wl] ABS-EXPR, ABS-EXPR, ABS-EXPR' ========================================== Pad the location counter (in the current subsection) to a particular storage boundary. The first expression (which must be absolute) is the alignment request in bytes. For example `.balign 8' advances the location counter until it is a multiple of 8. If the location counter is already a multiple of 8, no change is needed. The second expression (also absolute) gives the fill value to be stored in the padding bytes. It (and the comma) may be omitted. If it is omitted, the padding bytes are normally zero. However, on some systems, if the section is marked as containing code and the fill value is omitted, the space is filled with no-op instructions. The third expression is also absolute, and is also optional. If it is present, it is the maximum number of bytes that should be skipped by this alignment directive. If doing the alignment would require skipping more bytes than the specified maximum, then the alignment is not done at all. You can omit the fill value (the second argument) entirely by simply using two commas after the required alignment; this can be useful if you want the alignment to be filled with no-op instructions when appropriate. The `.balignw' and `.balignl' directives are variants of the `.balign' directive. The `.balignw' directive treats the fill pattern as a two byte word value. The `.balignl' directives treats the fill pattern as a four byte longword value. For example, `.balignw 4,0x368d' will align to a multiple of 4. If it skips two bytes, they will be filled in with the value 0x368d (the exact placement of the bytes depends upon the endianness of the processor). If it skips 1 or 3 bytes, the fill value is undefined.  File: as.info, Node: Byte, Next: Comm, Prev: Balign, Up: Pseudo Ops `.byte EXPRESSIONS' =================== `.byte' expects zero or more expressions, separated by commas. Each expression is assembled into the next byte.  File: as.info, Node: Comm, Next: Data, Prev: Byte, Up: Pseudo Ops `.comm SYMBOL , LENGTH ' ======================== `.comm' declares a common symbol named SYMBOL. When linking, a common symbol in one object file may be merged with a defined or common symbol of the same name in another object file. If `ld' does not see a definition for the symbol-just one or more common symbols-then it will allocate LENGTH bytes of uninitialized memory. LENGTH must be an absolute expression. If `ld' sees multiple common symbols with the same name, and they do not all have the same size, it will allocate space using the largest size. When using ELF, the `.comm' directive takes an optional third argument. This is the desired alignment of the symbol, specified as a byte boundary (for example, an alignment of 16 means that the least significant 4 bits of the address should be zero). The alignment must be an absolute expression, and it must be a power of two. If `ld' allocates uninitialized memory for the common symbol, it will use the alignment when placing the symbol. If no alignment is specified, `as' will set the alignment to the largest power of two less than or equal to the size of the symbol, up to a maximum of 16. The syntax for `.comm' differs slightly on the HPPA. The syntax is `SYMBOL .comm, LENGTH'; SYMBOL is optional.  File: as.info, Node: Data, Next: Def, Prev: Comm, Up: Pseudo Ops `.data SUBSECTION' ================== `.data' tells `as' to assemble the following statements onto the end of the data subsection numbered SUBSECTION (which is an absolute expression). If SUBSECTION is omitted, it defaults to zero.  File: as.info, Node: Def, Next: Desc, Prev: Data, Up: Pseudo Ops `.def NAME' =========== Begin defining debugging information for a symbol NAME; the definition extends until the `.endef' directive is encountered. This directive is only observed when `as' is configured for COFF format output; when producing `b.out', `.def' is recognized, but ignored.  File: as.info, Node: Desc, Next: Dim, Prev: Def, Up: Pseudo Ops `.desc SYMBOL, ABS-EXPRESSION' ============================== This directive sets the descriptor of the symbol (*note Symbol Attributes::) to the low 16 bits of an absolute expression. The `.desc' directive is not available when `as' is configured for COFF output; it is only for `a.out' or `b.out' object format. For the sake of compatibility, `as' accepts it, but produces no output, when configured for COFF.  File: as.info, Node: Dim, Next: Double, Prev: Desc, Up: Pseudo Ops `.dim' ====== This directive is generated by compilers to include auxiliary debugging information in the symbol table. It is only permitted inside `.def'/`.endef' pairs. `.dim' is only meaningful when generating COFF format output; when `as' is generating `b.out', it accepts this directive but ignores it.  File: as.info, Node: Double, Next: Eject, Prev: Dim, Up: Pseudo Ops `.double FLONUMS' ================= `.double' expects zero or more flonums, separated by commas. It assembles floating point numbers. The exact kind of floating point numbers emitted depends on how `as' is configured. *Note Machine Dependencies::.  File: as.info, Node: Eject, Next: Else, Prev: Double, Up: Pseudo Ops `.eject' ======== Force a page break at this point, when generating assembly listings.  File: as.info, Node: Else, Next: Elseif, Prev: Eject, Up: Pseudo Ops `.else' ======= `.else' is part of the `as' support for conditional assembly; *note `.if': If.. It marks the beginning of a section of code to be assembled if the condition for the preceding `.if' was false.  File: as.info, Node: Elseif, Next: End, Prev: Else, Up: Pseudo Ops `.elseif' ========= `.elseif' is part of the `as' support for conditional assembly; *note `.if': If.. It is shorthand for beginning a new `.if' block that would otherwise fill the entire `.else' section.  File: as.info, Node: End, Next: Endef, Prev: Elseif, Up: Pseudo Ops `.end' ====== `.end' marks the end of the assembly file. `as' does not process anything in the file past the `.end' directive.  File: as.info, Node: Endef, Next: Endfunc, Prev: End, Up: Pseudo Ops `.endef' ======== This directive flags the end of a symbol definition begun with `.def'. `.endef' is only meaningful when generating COFF format output; if `as' is configured to generate `b.out', it accepts this directive but ignores it.  File: as.info, Node: Endfunc, Next: Endif, Prev: Endef, Up: Pseudo Ops `.endfunc' ========== `.endfunc' marks the end of a function specified with `.func'.  File: as.info, Node: Endif, Next: Equ, Prev: Endfunc, Up: Pseudo Ops `.endif' ======== `.endif' is part of the `as' support for conditional assembly; it marks the end of a block of code that is only assembled conditionally. *Note `.if': If.  File: as.info, Node: Equ, Next: Equiv, Prev: Endif, Up: Pseudo Ops `.equ SYMBOL, EXPRESSION' ========================= This directive sets the value of SYMBOL to EXPRESSION. It is synonymous with `.set'; *note `.set': Set.. The syntax for `equ' on the HPPA is `SYMBOL .equ EXPRESSION'.  File: as.info, Node: Equiv, Next: Err, Prev: Equ, Up: Pseudo Ops `.equiv SYMBOL, EXPRESSION' =========================== The `.equiv' directive is like `.equ' and `.set', except that the assembler will signal an error if SYMBOL is already defined. Except for the contents of the error message, this is roughly equivalent to .ifdef SYM .err .endif .equ SYM,VAL  File: as.info, Node: Err, Next: Exitm, Prev: Equiv, Up: Pseudo Ops `.err' ====== If `as' assembles a `.err' directive, it will print an error message and, unless the `-Z' option was used, it will not generate an object file. This can be used to signal error an conditionally compiled code.  File: as.info, Node: Exitm, Next: Extern, Prev: Err, Up: Pseudo Ops `.exitm' ======== Exit early from the current macro definition. *Note Macro::.  File: as.info, Node: Extern, Next: Fail, Prev: Exitm, Up: Pseudo Ops `.extern' ========= `.extern' is accepted in the source program--for compatibility with other assemblers--but it is ignored. `as' treats all undefined symbols as external.  File: as.info, Node: Fail, Next: File, Prev: Extern, Up: Pseudo Ops `.fail EXPRESSION' ================== Generates an error or a warning. If the value of the EXPRESSION is 500 or more, `as' will print a warning message. If the value is less than 500, `as' will print an error message. The message will include the value of EXPRESSION. This can occasionally be useful inside complex nested macros or conditional assembly.  File: as.info, Node: File, Next: Fill, Prev: Fail, Up: Pseudo Ops `.file STRING' ============== `.file' tells `as' that we are about to start a new logical file. STRING is the new file name. In general, the filename is recognized whether or not it is surrounded by quotes `"'; but if you wish to specify an empty file name, you must give the quotes-`""'. This statement may go away in future: it is only recognized to be compatible with old `as' programs. In some configurations of `as', `.file' has already been removed to avoid conflicts with other assemblers. *Note Machine Dependencies::.  File: as.info, Node: Fill, Next: Float, Prev: File, Up: Pseudo Ops `.fill REPEAT , SIZE , VALUE' ============================= RESULT, SIZE and VALUE are absolute expressions. This emits REPEAT copies of SIZE bytes. REPEAT may be zero or more. SIZE may be zero or more, but if it is more than 8, then it is deemed to have the value 8, compatible with other people's assemblers. The contents of each REPEAT bytes is taken from an 8-byte number. The highest order 4 bytes are zero. The lowest order 4 bytes are VALUE rendered in the byte-order of an integer on the computer `as' is assembling for. Each SIZE bytes in a repetition is taken from the lowest order SIZE bytes of this number. Again, this bizarre behavior is compatible with other people's assemblers. SIZE and VALUE are optional. If the second comma and VALUE are absent, VALUE is assumed zero. If the first comma and following tokens are absent, SIZE is assumed to be 1.  File: as.info, Node: Float, Next: Func, Prev: Fill, Up: Pseudo Ops `.float FLONUMS' ================ This directive assembles zero or more flonums, separated by commas. It has the same effect as `.single'. The exact kind of floating point numbers emitted depends on how `as' is configured. *Note Machine Dependencies::.  File: as.info, Node: Func, Next: Global, Prev: Float, Up: Pseudo Ops `.func NAME[,LABEL]' ==================== `.func' emits debugging information to denote function NAME, and is ignored unless the file is assembled with debugging enabled. Only `--gstabs' is currently supported. LABEL is the entry point of the function and if omitted NAME prepended with the `leading char' is used. `leading char' is usually `_' or nothing, depending on the target. All functions are currently defined to have `void' return type. The function must be terminated with `.endfunc'.