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 \input texinfo @c -*- Texinfo -*- @setfilename gasp.info @c @c This file documents the assembly preprocessor "GASP" @c @c Copyright 1994, 1995, 2000 Free Software Foundation, Inc. @c @c Permission is granted to copy, distribute and/or modify this document @c under the terms of the GNU Free Documentation License, Version 1.1 @c or any later version published by the Free Software Foundation; @c with no Invariant Sections, with no Front-Cover Texts, and with no @c Back-Cover Texts. A copy of the license is included in the @c section entitled "GNU Free Documentation License". @ifinfo @format START-INFO-DIR-ENTRY * gasp: (gasp). The GNU Assembler Preprocessor END-INFO-DIR-ENTRY @end format @end ifinfo @syncodeindex ky cp @syncodeindex fn cp @finalout @setchapternewpage odd @settitle GASP @titlepage @c FIXME boring title @title GASP, an assembly preprocessor @subtitle for GASP version 1 @sp 1 @subtitle March 1994 @author Roland Pesch @page @tex {\parskip=0pt \hfill Cygnus Support\par } @end tex @vskip 0pt plus 1filll Copyright @copyright{} 1994, 1995, 2000 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". @end titlepage @ifinfo Copyright @copyright{} 1994, 1995, 2000 Free Software Foundation, Inc. @ignore Permission is granted to process this file through TeX and print the results, provided the printed document carries a copying permission notice identical to this one except for the removal of this paragraph (this paragraph not being relevant to the printed manual). @end ignore 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". @node Top @top GASP GASP is a preprocessor for assembly programs. This file describes version 1 of GASP. Steve Chamberlain wrote GASP; Roland Pesch wrote this manual. @menu * Overview:: What is GASP? * Invoking GASP:: Command line options. * Commands:: Preprocessor commands. * GNU Free Documentation License:: GNU Free Documentation License * Index:: Index. @end menu @end ifinfo @node Overview @chapter What is GASP? The primary purpose of the @sc{gnu} assembler is to assemble the output of other programs---notably compilers. When you have to hand-code specialized routines in assembly, that means the @sc{gnu} assembler is an unfriendly processor: it has no directives for macros, conditionals, or many other conveniences that you might expect. In some cases you can simply use the C preprocessor, or a generalized preprocessor like @sc{m4}; but this can be awkward, since none of these things are designed with assembly in mind. @sc{gasp} fills this need. It is expressly designed to provide the facilities you need with hand-coded assembly code. Implementing it as a preprocessor, rather than part of the assembler, allows the maximum flexibility: you can use it with hand-coded assembly, without paying a penalty of added complexity in the assembler you use for compiler output. Here is a small example to give the flavor of @sc{gasp}. This input to @sc{gasp} @cartouche @example .MACRO saveregs from=8 to=14 count .ASSIGNA \from ! save r\from..r\to .AWHILE \&count LE \to mov r\&count,@@-sp count .ASSIGNA \&count + 1 .AENDW .ENDM saveregs from=12 bar: mov #H'dead+10,r0 foo .SDATAC "hello"<10> .END @end example @end cartouche @noindent generates this assembly program: @cartouche @example ! save r12..r14 mov r12,@@-sp mov r13,@@-sp mov r14,@@-sp bar: mov #57005+10,r0 foo: .byte 6,104,101,108,108,111,10 @end example @end cartouche @node Invoking GASP @chapter Command Line Options @c FIXME! Or is there a simpler way, calling from GAS option? The simplest way to use @sc{gasp} is to run it as a filter and assemble its output. In Unix and its ilk, you can do this, for example: @c FIXME! GASP filename suffix convention? @example gasp prog.asm | as -o prog.o @end example Naturally, there are also a few command-line options to allow you to request variations on this basic theme. Here is the full set of possibilities for the @sc{gasp} command line. @example gasp [ -a | --alternate ] [ -c @var{char} | --commentchar @var{char} ] [ -d | --debug ] [ -h | --help ] [ -M | --mri ] [ -o @var{outfile} | --output @var{outfile} ] [ -p | --print ] [ -s | --copysource ] [ -u | --unreasonable ] [ -v | --version ] @var{infile} @dots{} @end example @ftable @code @item @var{infile} @dots{} @c FIXME! Why not stdin as default infile? The input file names. You must specify at least one input file; if you specify more, @sc{gasp} preprocesses them all, concatenating the output in the order you list the @var{infile} arguments. Mark the end of each input file with the preprocessor command @code{.END}. @xref{Other Commands,, Miscellaneous commands}. @item -a @itemx --alternate Use alternative macro syntax. @xref{Alternate,, Alternate macro syntax}, for a discussion of how this syntax differs from the default @sc{gasp} syntax. @cindex comment character, changing @cindex semicolon, as comment @cindex exclamation mark, as comment @cindex shriek, as comment @cindex bang, as comment @cindex @code{!} default comment char @cindex @code{;} as comment char @item -c '@var{char}' @itemx --commentchar '@var{char}' Use @var{char} as the comment character. The default comment character is @samp{!}. For example, to use a semicolon as the comment character, specify @w{@samp{-c ';'}} on the @sc{gasp} command line. Since assembler command characters often have special significance to command shells, it is a good idea to quote or escape @var{char} when you specify a comment character. For the sake of simplicity, all examples in this manual use the default comment character @samp{!}. @item -d @itemx --debug Show debugging statistics. In this version of @sc{gasp}, this option produces statistics about the string buffers that @sc{gasp} allocates internally. For each defined buffersize @var{s}, @sc{gasp} shows the number of strings @var{n} that it allocated, with a line like this: @example strings size @var{s} : @var{n} @end example @noindent @sc{gasp} displays these statistics on the standard error stream, when done preprocessing. @item -h @itemx --help Display a summary of the @sc{gasp} command line options. @item -M @itemx --mri Use MRI compatibility mode. Using this option causes @sc{gasp} to accept the syntax and pseudo-ops used by the Microtec Research @code{ASM68K} assembler. @item -o @var{outfile} @itemx --output @var{outfile} Write the output in a file called @var{outfile}. If you do not use the @samp{-o} option, @sc{gasp} writes its output on the standard output stream. @item -p @itemx --print Print line numbers. @sc{gasp} obeys this option @emph{only} if you also specify @samp{-s} to copy source lines to its output. With @samp{-s -p}, @sc{gasp} displays the line number of each source line copied (immediately after the comment character at the beginning of the line). @item -s @itemx --copysource Copy the source lines to the output file. Use this option to see the effect of each preprocessor line on the @sc{gasp} output. @sc{gasp} places a comment character (@samp{!} by default) at the beginning of each source line it copies, so that you can use this option and still assemble the result. @item -u @itemx --unreasonable Bypass unreasonable expansion'' limit. Since you can define @sc{gasp} macros inside other macro definitions, the preprocessor normally includes a sanity check. If your program requires more than 1,000 nested expansions, @sc{gasp} normally exits with an error message. Use this option to turn off this check, allowing unlimited nested expansions. @item -v @itemx --version Display the @sc{gasp} version number. @end ftable @node Commands @chapter Preprocessor Commands @sc{gasp} commands have a straightforward syntax that fits in well with assembly conventions. In general, a command extends for a line, and may have up to three fields: an optional label, the command itself, and optional arguments to the command. You can write commands in upper or lower case, though this manual shows them in upper case. @xref{Syntax Details,, Details of the GASP syntax}, for more information. @menu * Conditionals:: * Loops:: * Variables:: * Macros:: * Data:: * Listings:: * Other Commands:: * Syntax Details:: * Alternate:: @end menu @node Conditionals @section Conditional assembly The conditional-assembly directives allow you to include or exclude portions of an assembly depending on how a pair of expressions, or a pair of strings, compare. The overall structure of conditionals is familiar from many other contexts. @code{.AIF} marks the start of a conditional, and precedes assembly for the case when the condition is true. An optional @code{.AELSE} precedes assembly for the converse case, and an @code{.AENDI} marks the end of the condition. @c FIXME! Why doesn't -u turn off this check? You may nest conditionals up to a depth of 100; @sc{gasp} rejects nesting beyond that, because it may indicate a bug in your macro structure. @c FIXME! Why isn't there something like cpp's -D option? Conditionals @c would be much more useful if there were. Conditionals are primarily useful inside macro definitions, where you often need different effects depending on argument values. @xref{Macros,, Defining your own directives}, for details about defining macros. @ftable @code @item .AIF @var{expra} @var{cmp} @var{exprb} @itemx .AIF "@var{stra}" @var{cmp} "@var{strb}" The governing condition goes on the same line as the @code{.AIF} preprocessor command. You may compare either two strings, or two expressions. When you compare strings, only two conditional @var{cmp} comparison operators are available: @samp{EQ} (true if @var{stra} and @var{strb} are identical), and @samp{NE} (the opposite). When you compare two expressions, @emph{both expressions must be absolute} (@pxref{Expressions,, Arithmetic expressions in GASP}). You can use these @var{cmp} comparison operators with expressions: @ftable @code @item EQ Are @var{expra} and @var{exprb} equal? (For strings, are @var{stra} and @var{strb} identical?) @item NE Are @var{expra} and @var{exprb} different? (For strings, are @var{stra} and @var{strb} different? @item LT Is @var{expra} less than @var{exprb}? (Not allowed for strings.) @item LE Is @var{expra} less than or equal to @var{exprb}? (Not allowed for strings.) @item GT Is @var{expra} greater than @var{exprb}? (Not allowed for strings.) @item GE Is @var{expra} greater than or equal to @var{exprb}? (Not allowed for strings.) @end ftable @item .AELSE Marks the start of assembly code to be included if the condition fails. Optional, and only allowed within a conditional (between @code{.AIF} and @code{.AENDI}). @item .AENDI Marks the end of a conditional assembly. @end ftable @node Loops @section Repetitive sections of assembly Two preprocessor directives allow you to repeatedly issue copies of the same block of assembly code. @ftable @code @item .AREPEAT @var{aexp} @itemx .AENDR If you simply need to repeat the same block of assembly over and over a fixed number of times, sandwich one instance of the repeated block between @code{.AREPEAT} and @code{.AENDR}. Specify the number of copies as @var{aexp} (which must be an absolute expression). For example, this repeats two assembly statements three times in succession: @cartouche @example .AREPEAT 3 rotcl r2 div1 r0,r1 .AENDR @end example @end cartouche @item .AWHILE @var{expra} @var{cmp} @var{exprb} @itemx .AENDW @itemx .AWHILE @var{stra} @var{cmp} @var{strb} @itemx .AENDW To repeat a block of assembly depending on a conditional test, rather than repeating it for a specific number of times, use @code{.AWHILE}. @code{.AENDW} marks the end of the repeated block. The conditional comparison works exactly the same way as for @code{.AIF}, with the same comparison operators (@pxref{Conditionals,, Conditional assembly}). Since the terms of the comparison must be absolute expression, @code{.AWHILE} is primarily useful within macros. @xref{Macros,, Defining your own directives}. @end ftable @cindex loops, breaking out of @cindex breaking out of loops You can use the @code{.EXITM} preprocessor directive to break out of loops early (as well as to break out of macros). @xref{Macros,, Defining your own directives}. @node Variables @section Preprocessor variables You can use variables in @sc{gasp} to represent strings, registers, or the results of expressions. You must distinguish two kinds of variables: @enumerate @item Variables defined with @code{.EQU} or @code{.ASSIGN}. To evaluate this kind of variable in your assembly output, simply mention its name. For example, these two lines define and use a variable @samp{eg}: @cartouche @example eg .EQU FLIP-64 @dots{} mov.l eg,r0 @end example @end cartouche @emph{Do not use} this kind of variable in conditional expressions or while loops; @sc{gasp} only evaluates these variables when writing assembly output. @item Variables for use during preprocessing. You can define these with @code{.ASSIGNC} or @code{.ASSIGNA}. To evaluate this kind of variable, write @samp{\&} before the variable name; for example, @cartouche @example opcit .ASSIGNA 47 @dots{} .AWHILE \&opcit GT 0 @dots{} .AENDW @end example @end cartouche @sc{gasp} treats macro arguments almost the same way, but to evaluate them you use the prefix @samp{\} rather than @samp{\&}. @xref{Macros,, Defining your own directives}. @end enumerate @ftable @code @item @var{pvar} .EQU @var{expr} @c FIXME! Anything to beware of re GAS directive of same name? Assign preprocessor variable @var{pvar} the value of the expression @var{expr}. There are no restrictions on redefinition; use @samp{.EQU} with the same @var{pvar} as often as you find it convenient. @item @var{pvar} .ASSIGN @var{expr} Almost the same as @code{.EQU}, save that you may not redefine @var{pvar} using @code{.ASSIGN} once it has a value. @c FIXME!! Supposed to work this way, apparently, but on 9feb94 works @c just like .EQU @item @var{pvar} .ASSIGNA @var{aexpr} Define a variable with a numeric value, for use during preprocessing. @var{aexpr} must be an absolute expression. You can redefine variables with @code{.ASSIGNA} at any time. @item @var{pvar} .ASSIGNC "@var{str}" Define a variable with a string value, for use during preprocessing. You can redefine variables with @code{.ASSIGNC} at any time. @item @var{pvar} .REG (@var{register}) Use @code{.REG} to define a variable that represents a register. In particular, @var{register} is @emph{not evaluated} as an expression. You may use @code{.REG} at will to redefine register variables. @end ftable All these directives accept the variable name in the label'' position, that is at the left margin. You may specify a colon after the variable name if you wish; the first example above could have started @samp{eg:} with the same effect. @c pagebreak makes for better aesthetics---ensures macro and expansion together @page @node Macros @section Defining your own directives The commands @code{.MACRO} and @code{.ENDM} allow you to define macros that generate assembly output. You can use these macros with a syntax similar to built-in @sc{gasp} or assembler directives. For example, this definition specifies a macro @code{SUM} that adds together a range of consecutive registers: @cartouche @example .MACRO SUM FROM=0, TO=9 ! \FROM \TO mov r\FROM,r10 COUNT .ASSIGNA \FROM+1 .AWHILE \&COUNT LE \TO add r\&COUNT,r10 COUNT .ASSIGNA \&COUNT+1 .AENDW .ENDM @end example @end cartouche @noindent With that definition, @samp{SUM 0,5} generates this assembly output: @cartouche @example ! 0 5 mov r0,r10 add r1,r10 add r2,r10 add r3,r10 add r4,r10 add r5,r10 @end example @end cartouche @ftable @code @item .MACRO @var{macname} @itemx .MACRO @var{macname} @var{macargs} @dots{} Begin the definition of a macro called @var{macname}. If your macro definition requires arguments, specify their names after the macro name, separated by commas or spaces. You can supply a default value for any macro argument by following the name with @samp{=@var{deflt}}. For example, these are all valid @code{.MACRO} statements: @table @code @item .MACRO COMM Begin the definition of a macro called @code{COMM}, which takes no arguments. @item .MACRO PLUS1 P, P1 @itemx .MACRO PLUS1 P P1 Either statement begins the definition of a macro called @code{PLUS1}, which takes two arguments; within the macro definition, write @samp{\P} or @samp{\P1} to evaluate the arguments. @item .MACRO RESERVE_STR P1=0 P2 Begin the definition of a macro called @code{RESERVE_STR}, with two arguments. The first argument has a default value, but not the second. After the definition is complete, you can call the macro either as @samp{RESERVE_STR @var{a},@var{b}} (with @samp{\P1} evaluating to @var{a} and @samp{\P2} evaluating to @var{b}), or as @samp{RESERVE_STR ,@var{b}} (with @samp{\P1} evaluating as the default, in this case @samp{0}, and @samp{\P2} evaluating to @var{b}). @end table When you call a macro, you can specify the argument values either by position, or by keyword. For example, @samp{SUM 9,17} is equivalent to @samp{SUM TO=17, FROM=9}. Macro arguments are preprocessor variables similar to the variables you define with @samp{.ASSIGNA} or @samp{.ASSIGNC}; in particular, you can use them in conditionals or for loop control. (The only difference is the prefix you write to evaluate the variable: for a macro argument, write @samp{\@var{argname}}, but for a preprocessor variable, write @samp{\&@var{varname}}.) @item @var{name} .MACRO @itemx @var{name} .MACRO ( @var{macargs} @dots{} ) @c FIXME check: I think no error _and_ no args recognized if I use form @c NAME .MACRO ARG ARG An alternative form of introducing a macro definition: specify the macro name in the label position, and the arguments (if any) between parentheses after the name. Defaulting rules and usage work the same way as for the other macro definition syntax. @item .ENDM Mark the end of a macro definition. @item .EXITM Exit early from the current macro definition, @code{.AREPEAT} loop, or @code{.AWHILE} loop. @cindex number of macros executed @cindex macros, count executed @item \@@ @sc{gasp} maintains a counter of how many macros it has executed in this pseudo-variable; you can copy that number to your output with @samp{\@@}, but @emph{only within a macro definition}. @item LOCAL @var{name} [ , @dots{} ] @emph{Warning: @code{LOCAL} is only available if you select alternate macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,, Alternate macro syntax}. Generate a string replacement for each of the @var{name} arguments, and replace any instances of @var{name} in each macro expansion. The replacement string is unique in the assembly, and different for each separate macro expansion. @code{LOCAL} allows you to write macros that define symbols, without fear of conflict between separate macro expansions. @end ftable @node Data @section Data output In assembly code, you often need to specify working areas of memory; depending on the application, you may want to initialize such memory or not. @sc{gasp} provides preprocessor directives to help you avoid repetitive coding for both purposes. You can use labels as usual to mark the data areas. @menu * Initialized:: * Uninitialized:: @end menu @node Initialized @subsection Initialized data These are the @sc{gasp} directives for initialized data, and the standard @sc{gnu} assembler directives they expand to: @ftable @code @item .DATA @var{expr}, @var{expr}, @dots{} @itemx .DATA.B @var{expr}, @var{expr}, @dots{} @itemx .DATA.W @var{expr}, @var{expr}, @dots{} @itemx .DATA.L @var{expr}, @var{expr}, @dots{} Evaluate arithmetic expressions @var{expr}, and emit the corresponding @code{as} directive (labelled with @var{lab}). The unqualified @code{.DATA} emits @samp{.long}; @code{.DATA.B} emits @samp{.byte}; @code{.DATA.W} emits @samp{.short}; and @code{.DATA.L} emits @samp{.long}. For example, @samp{foo .DATA 1,2,3} emits @samp{foo: .long 1,2,3}. @item .DATAB @var{repeat}, @var{expr} @itemx .DATAB.B @var{repeat}, @var{expr} @itemx .DATAB.W @var{repeat}, @var{expr} @itemx .DATAB.L @var{repeat}, @var{expr} @c FIXME! Looks like gasp accepts and ignores args after 2nd. Make @code{as} emit @var{repeat} copies of the value of the expression @var{expr} (using the @code{as} directive @code{.fill}). @samp{.DATAB.B} repeats one-byte values; @samp{.DATAB.W} repeats two-byte values; and @samp{.DATAB.L} repeats four-byte values. @samp{.DATAB} without a suffix repeats four-byte values, just like @samp{.DATAB.L}. @c FIXME! Allowing zero might be useful for edge conditions in macros. @var{repeat} must be an absolute expression with a positive value. @item .SDATA "@var{str}" @dots{} String data. Emits a concatenation of bytes, precisely as you specify them (in particular, @emph{nothing is added to mark the end} of the string). @xref{Constants,, String and numeric constants}, for details about how to write strings. @code{.SDATA} concatenates multiple arguments, making it easy to switch between string representations. You can use commas to separate the individual arguments for clarity, if you choose. @item .SDATAB @var{repeat}, "@var{str}" @dots{} Repeated string data. The first argument specifies how many copies of the string to emit; the remaining arguments specify the string, in the same way as the arguments to @code{.SDATA}. @item .SDATAZ "@var{str}" @dots{} Zero-terminated string data. Just like @code{.SDATA}, except that @code{.SDATAZ} writes a zero byte at the end of the string. @item .SDATAC "@var{str}" @dots{} Count-prefixed string data. Just like @code{.SDATA}, except that @sc{gasp} precedes the string with a leading one-byte count. For example, @samp{.SDATAC "HI"} generates @samp{.byte 2,72,73}. Since the count field is only one byte, you can only use @code{.SDATAC} for strings less than 256 bytes in length. @end ftable @node Uninitialized @subsection Uninitialized data @c FIXME! .space different on some platforms, notably HPPA. Config? Use the @code{.RES}, @code{.SRES}, @code{.SRESC}, and @code{.SRESZ} directives to reserve memory and leave it uninitialized. @sc{gasp} resolves these directives to appropriate calls of the @sc{gnu} @code{as} @code{.space} directive. @ftable @code @item .RES @var{count} @itemx .RES.B @var{count} @itemx .RES.W @var{count} @itemx .RES.L @var{count} Reserve room for @var{count} uninitialized elements of data. The suffix specifies the size of each element: @code{.RES.B} reserves @var{count} bytes, @code{.RES.W} reserves @var{count} pairs of bytes, and @code{.RES.L} reserves @var{count} quartets. @code{.RES} without a suffix is equivalent to @code{.RES.L}. @item .SRES @var{count} @itemx .SRES.B @var{count} @itemx .SRES.W @var{count} @itemx .SRES.L @var{count} @c FIXME! This is boring. Shouldn't it at least have a different @c default size? (e.g. the "S" suggests "string", for which .B @c would be more appropriate) @code{.SRES} is a synonym for @samp{.RES}. @item .SRESC @var{count} @itemx .SRESC.B @var{count} @itemx .SRESC.W @var{count} @itemx .SRESC.L @var{count} Like @code{.SRES}, but reserves space for @code{@var{count}+1} elements. @item .SRESZ @var{count} @itemx .SRESZ.B @var{count} @itemx .SRESZ.W @var{count} @itemx .SRESZ.L @var{count} Like @code{.SRES}, but reserves space for @code{@var{count}+1} elements. @end ftable @node Listings @section Assembly listing control The @sc{gasp} listing-control directives correspond to related @sc{gnu} @code{as} directives. @ftable @code @item .PRINT LIST @itemx .PRINT NOLIST Print control. This directive emits the @sc{gnu} @code{as} directive @code{.list} or @code{.nolist}, according to its argument. @xref{List,, @code{.list}, as.info, Using as}, for details on how these directives interact. @item .FORM LIN=@var{ln} @itemx .FORM COL=@var{cols} @itemx .FORM LIN=@var{ln} COL=@var{cols} Specify the page size for assembly listings: @var{ln} represents the number of lines, and @var{cols} the number of columns. You may specify either page dimension independently, or both together. If you do not specify the number of lines, @sc{gasp} assumes 60 lines; if you do not specify the number of columns, @sc{gasp} assumes 132 columns. (Any values you may have specified in previous instances of @code{.FORM} do @emph{not} carry over as defaults.) Emits the @code{.psize} assembler directive. @item .HEADING @var{string} Specify @var{string} as the title of your assembly listings. Emits @samp{.title "@var{string}"}. @item .PAGE Force a new page in assembly listings. Emits @samp{.eject}. @end ftable @node Other Commands @section Miscellaneous commands @ftable @code @item .ALTERNATE Use the alternate macro syntax henceforth in the assembly. @xref{Alternate,, Alternate macro syntax}. @item .ORG @c FIXME! This is very strange, since _GAS_ understands .org This command is recognized, but not yet implemented. @sc{gasp} generates an error message for programs that use @code{.ORG}. @item .RADIX @var{s} @c FIXME no test cases in testsuite/gasp @sc{gasp} understands numbers in any of base two, eight, ten, or sixteen. You can encode the base explicitly in any numeric constant (@pxref{Constants,, String and numeric constants}). If you write numbers without an explicit indication of the base, the most recent @samp{.RADIX @var{s}} command determines how they are interpreted. @var{s} is a single letter, one of the following: @table @code @item .RADIX B Base 2. @item .RADIX Q Base 8. @item .RADIX D Base 10. This is the original default radix. @item .RADIX H Base 16. @end table You may specify the argument @var{s} in lower case (any of @samp{bqdh}) with the same effects. @item .EXPORT @var{name} @itemx .GLOBAL @var{name} @c FIXME! No test cases in testsuite/gasp Declare @var{name} global (emits @samp{.global @var{name}}). The two directives are synonymous. @item .PROGRAM No effect: @sc{gasp} accepts this directive, and silently ignores it. @item .END Mark end of each preprocessor file. @sc{gasp} issues a warning if it reaches end of file without seeing this command. @item .INCLUDE "@var{str}" Preprocess the file named by @var{str}, as if its contents appeared where the @code{.INCLUDE} directive does. @sc{gasp} imposes a maximum limit of 30 stacked include files, as a sanity check. @c FIXME! Why is include depth not affected by -u? @item .ALIGN @var{size} @c FIXME! Why is this not utterly pointless? Evaluate the absolute expression @var{size}, and emit the assembly instruction @samp{.align @var{size}} using the result. @end ftable @node Syntax Details @section Details of the GASP syntax Since @sc{gasp} is meant to work with assembly code, its statement syntax has no surprises for the assembly programmer. @cindex whitespace @emph{Whitespace} (blanks or tabs; @emph{not} newline) is partially significant, in that it delimits up to three fields in a line. The amount of whitespace does not matter; you may line up fields in separate lines if you wish, but @sc{gasp} does not require that. @cindex fields of @sc{gasp} source line @cindex label field The @emph{first field}, an optional @dfn{label}, must be flush left in a line (with no leading whitespace) if it appears at all. You may use a colon after the label if you wish; @sc{gasp} neither requires the colon nor objects to it (but will not include it as part of the label name). @cindex directive field The @emph{second field}, which must appear after some whitespace, contains a @sc{gasp} or assembly @dfn{directive}. @cindex argument fields Any @emph{further fields} on a line are @dfn{arguments} to the directive; you can separate them from one another using either commas or whitespace. @menu * Markers:: * Constants:: * Symbols:: * Expressions:: * String Builtins:: @end menu @node Markers @subsection Special syntactic markers @sc{gasp} recognizes a few special markers: to delimit comments, to continue a statement on the next line, to separate symbols from other characters, and to copy text to the output literally. (One other special marker, @samp{\@@}, works only within macro definitions; @pxref{Macros,, Defining your own directives}.) @cindex comments The trailing part of any @sc{gasp} source line may be a @dfn{comment}. A comment begins with the first unquoted comment character (@samp{!} by default), or an escaped or doubled comment character (@samp{\!} or @samp{!!} by default), and extends to the end of a line. You can specify what comment character to use with the @samp{-c} option (@pxref{Invoking GASP,, Command Line Options}). The two kinds of comment markers lead to slightly different treatment: @table @code @item ! A single, un-escaped comment character generates an assembly comment in the @sc{gasp} output. @sc{gasp} evaluates any preprocessor variables (macro arguments, or variables defined with @code{.ASSIGNA} or @code{.ASSIGNC}) present. For example, a macro that begins like this @example .MACRO SUM FROM=0, TO=9 ! \FROM \TO @end example @noindent issues as the first line of output a comment that records the values you used to call the macro. @c comments, preprocessor-only @c preprocessor-only comments @c GASP-only comments @item \! @itemx !! Either an escaped comment character, or a double comment character, marks a @sc{gasp} source comment. @sc{gasp} does not copy such comments to the assembly output. @end table @cindex continuation character @kindex + To @emph{continue a statement} on the next line of the file, begin the second line with the character @samp{+}. @cindex literal copy to output @cindex copying literally to output @cindex preprocessing, avoiding @cindex avoiding preprocessing Occasionally you may want to prevent @sc{gasp} from preprocessing some particular bit of text. To @emph{copy literally} from the @sc{gasp} source to its output, place @samp{\(} before the string to copy, and @samp{)} at the end. For example, write @samp{\(\!)} if you need the characters @samp{\!} in your assembly output. @cindex symbol separator @cindex text, separating from symbols @cindex symbols, separating from text To @emph{separate a preprocessor variable} from text to appear immediately after its value, write a single quote (@code{'}). For example, @samp{.SDATA "\P'1"} writes a string built by concatenating the value of @code{P} and the digit @samp{1}. (You cannot achieve this by writing just @samp{\P1}, since @samp{P1} is itself a valid name for a preprocessor variable.) @node Constants @subsection String and numeric constants There are two ways of writing @dfn{string constants} in @sc{gasp}: as literal text, and by numeric byte value. Specify a string literal between double quotes (@code{"@var{str}"}). Specify an individual numeric byte value as an absolute expression between angle brackets (@code{<@var{expr}>}. Directives that output strings allow you to specify any number of either kind of value, in whatever order is convenient, and concatenate the result. (Alternate syntax mode introduces a number of alternative string notations; @pxref{Alternate,, Alternate macro syntax}.) @c Details of numeric notation, e.g. base prefixes You can write @dfn{numeric constants} either in a specific base, or in whatever base is currently selected (either 10, or selected by the most recent @code{.RADIX}). To write a number in a @emph{specific base}, use the pattern @code{@var{s}'@var{ddd}}: a base specifier character @var{s}, followed by a single quote followed by digits @var{ddd}. The base specifier character matches those you can specify with @code{.RADIX}: @samp{B} for base 2, @samp{Q} for base 8, @samp{D} for base 10, and @samp{H} for base 16. (You can write this character in lower case if you prefer.) @c FIXME! What are rules for recognizing number in deflt base? Whatever @c is left over after parsing other things?? @node Symbols @subsection Symbols @sc{gasp} recognizes symbol names that start with any alphabetic character, @samp{_}, or @samp{}, and continue with any of the same characters or with digits. Label names follow the same rules. @node Expressions @subsection Arithmetic expressions in GASP @cindex absolute expressions @cindex relocatable expressions There are two kinds of expressions, depending on their result: @dfn{absolute} expressions, which resolve to a constant (that is, they do not involve any values unknown to @sc{gasp}), and @dfn{relocatable} expressions, which must reduce to the form @example @var{addsym}+@var{const}-@var{subsym} @end example @noindent where @var{addsym} and @var{subsym} are assembly symbols of unknown value, and @var{const} is a constant. Arithmetic for @sc{gasp} expressions follows very similar rules to C. You can use parentheses to change precedence; otherwise, arithmetic primitives have decreasing precedence in the order of the following list. @enumerate @item Single-argument @code{+} (identity), @code{-} (arithmetic opposite), or @code{~} (bitwise negation). @emph{The argument must be an absolute expression.} @item @code{*} (multiplication) and @code{/} (division). @emph{Both arguments must be absolute expressions.} @item @code{+} (addition) and @code{-} (subtraction). @emph{At least one argument must be absolute.} @c FIXME! Actually, subtraction doesn't check for this. @item @code{&} (bitwise and). @emph{Both arguments must be absolute.} @item @c FIXME! I agree ~ is a better notation than ^ for xor, but is the @c improvement worth differing from C? @code{|} (bitwise or) and @code{~} (bitwise exclusive or; @code{^} in C). @emph{Both arguments must be absolute.} @end enumerate @node String Builtins @subsection String primitives You can use these primitives to manipulate strings (in the argument field of @sc{gasp} statements): @ftable @code @item .LEN("@var{str}") Calculate the length of string @code{"@var{str}"}, as an absolute expression. For example, @samp{.RES.B .LEN("sample")} reserves six bytes of memory. @item .INSTR("@var{string}", "@var{seg}", @var{ix}) Search for the first occurrence of @var{seg} after position @var{ix} of @var{string}. For example, @samp{.INSTR("ABCDEFG", "CDE", 0)} evaluates to the absolute result @code{2}. The result is @code{-1} if @var{seg} does not occur in @var{string} after position @var{ix}. @item .SUBSTR("@var{string}",@var{start},@var{len}) The substring of @var{string} beginning at byte number @var{start} and extending for @var{len} bytes. @end ftable @node Alternate @section Alternate macro syntax If you specify @samp{-a} or @samp{--alternate} on the @sc{gasp} command line, the preprocessor uses somewhat different syntax. This syntax is reminiscent of the syntax of Phar Lap macro assembler, but it is @emph{not} meant to be a full emulation of Phar Lap or similar assemblers. In particular, @sc{gasp} does not support directives such as @code{DB} and @code{IRP}, even in alternate syntax mode. In particular, @samp{-a} (or @samp{--alternate}) elicits these differences: @table @emph @item Preprocessor directives You can use @sc{gasp} preprocessor directives without a leading @samp{.} dot. For example, you can write @samp{SDATA} with the same effect as @samp{.SDATA}. @item LOCAL One additional directive, @code{LOCAL}, is available. @xref{Macros,, Defining your own directives}, for an explanation of how to use @code{LOCAL}. @need 2000 @item String delimiters You can write strings delimited in these other ways besides @code{"@var{string}"}: @table @code @item '@var{string}' You can delimit strings with single-quote charaters. @item <@var{string}> You can delimit strings with matching angle brackets. @end table @item single-character string escape To include any single character literally in a string (even if the character would otherwise have some special meaning), you can prefix the character with @samp{!} (an exclamation mark). For example, you can write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}. @item Expression results as strings You can write @samp{%@var{expr}} to evaluate the expression @var{expr} and use the result as a string. @end table @node GNU Free Documentation License @chapter GNU Free Documentation License GNU Free Documentation License Version 1.1, March 2000 Copyright (C) 2000 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed. 0. PREAMBLE The purpose of this License is to make a manual, textbook, or other written document "free" in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. 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TERMINATION You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance. 10. FUTURE REVISIONS OF THIS LICENSE The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/. Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License "or any later version" applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation. ADDENDUM: How to use this License for your documents To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page: @smallexample Copyright (c) YEAR YOUR NAME. 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 the Invariant Sections being LIST THEIR TITLES, with the Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST. A copy of the license is included in the section entitled "GNU Free Documentation License". @end smallexample If you have no Invariant Sections, write "with no Invariant Sections" instead of saying which ones are invariant. If you have no Front-Cover Texts, write "no Front-Cover Texts" instead of "Front-Cover Texts being LIST"; likewise for Back-Cover Texts. If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software. @node Index @unnumbered Index @printindex cp @contents @bye