225 lines
8.5 KiB
Plaintext
225 lines
8.5 KiB
Plaintext
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@c Copyright (C) 2003, 2004, 2005 Free Software Foundation, Inc.
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@c This is part of the GCC manual.
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@c For copying conditions, see the file gcc.texi.
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@node Options
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@chapter Option specification files
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@cindex option specification files
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@cindex @samp{opts.sh}
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Most GCC command-line options are described by special option
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definition files, the names of which conventionally end in
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@code{.opt}. This chapter describes the format of these files.
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@menu
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* Option file format:: The general layout of the files
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* Option properties:: Supported option properties
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@end menu
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@node Option file format
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@section Option file format
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Option files are a simple list of records in which each field occupies
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its own line and in which the records themselves are separated by
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blank lines. Comments may appear on their own line anywhere within
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the file and are preceded by semicolons. Whitespace is allowed before
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the semicolon.
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The files can contain the following types of record:
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@itemize @bullet
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@item
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A language definition record. <20>These records have two fields: the
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string @samp{Language} and the name of the language. <20>Once a language
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has been declared in this way, it can be used as an option property.
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@xref{Option properties}.
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@item
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An option definition record. <20>These records have the following fields:
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@enumerate
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@item
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the name of the option, with the leading ``-'' removed
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@item
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a space-separated list of option properties (@pxref{Option properties})
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@item
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the help text to use for @option{--help} (omitted if the second field
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contains the @code{Undocumented} property).
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@end enumerate
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By default, all options beginning with ``f'', ``W'' or ``m'' are
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implicitly assumed to take a ``no-'' form. This form should not be
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listed separately. If an option beginning with one of these letters
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does not have a ``no-'' form, you can use the @code{RejectNegative}
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property to reject it.
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The help text is automatically line-wrapped before being displayed.
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Normally the name of the option is printed on the left-hand side of
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the output and the help text is printed on the right. However, if the
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help text contains a tab character, the text to the left of the tab is
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used instead of the option's name and the text to the right of the
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tab forms the help text. This allows you to elaborate on what type
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of argument the option takes.
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@item
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A target mask record. <20>These records have one field of the form
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@samp{Mask(@var{x})}. <20>The options-processing script will automatically
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allocate a bit in @code{target_flags} (@pxref{Run-time Target}) for
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each mask name @var{x} and set the macro @code{MASK_@var{x}} to the
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appropriate bitmask. <20>It will also declare a @code{TARGET_@var{x}}
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macro that has the value 1 when bit @code{MASK_@var{x}} is set and
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0 otherwise.
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They are primarily intended to declare target masks that are not
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associated with user options, either because these masks represent
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internal switches or because the options are not available on all
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configurations and yet the masks always need to be defined.
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@end itemize
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@node Option properties
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@section Option properties
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The second field of an option record can specify the following properties:
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@table @code
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@item Common
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The option is available for all languages and targets.
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@item Target
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The option is available for all languages but is target-specific.
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@item @var{language}
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The option is available when compiling for the given language.
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It is possible to specify several different languages for the same
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option. Each @var{language} must have been declared by an earlier
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@code{Language} record. @xref{Option file format}.
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@item RejectNegative
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The option does not have a ``no-'' form. All options beginning with
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``f'', ``W'' or ``m'' are assumed to have a ``no-'' form unless this
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property is used.
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@item Negative(@var{othername})
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The option will turn off another option @var{othername}, which is the
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the option name with the leading ``-'' removed. This chain action will
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propagate through the @code{Negative} property of the option to be
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turned off.
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@item Joined
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@itemx Separate
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The option takes a mandatory argument. @code{Joined} indicates
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that the option and argument can be included in the same @code{argv}
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entry (as with @code{-mflush-func=@var{name}}, for example).
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@code{Separate} indicates that the option and argument can be
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separate @code{argv} entries (as with @code{-o}). An option is
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allowed to have both of these properties.
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@item JoinedOrMissing
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The option takes an optional argument. If the argument is given,
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it will be part of the same @code{argv} entry as the option itself.
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This property cannot be used alongside @code{Joined} or @code{Separate}.
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@item UInteger
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The option's argument is a non-negative integer. The option parser
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will check and convert the argument before passing it to the relevant
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option handler.
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@item Var(@var{var})
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The state of this option should be stored in variable @var{var}.
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The way that the state is stored depends on the type of option:
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@itemize @bullet
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@item
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If the option uses the @code{Mask} or @code{InverseMask} properties,
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@var{var} is the integer variable that contains the mask.
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@item
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If the option is a normal on/off switch, @var{var} is an integer
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variable that is nonzero when the option is enabled. The options
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parser will set the variable to 1 when the positive form of the
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option is used and 0 when the ``no-'' form is used.
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@item
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If the option takes an argument and has the @code{UInteger} property,
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@var{var} is an integer variable that stores the value of the argument.
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@item
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Otherwise, if the option takes an argument, @var{var} is a pointer to
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the argument string. The pointer will be null if the argument is optional
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and wasn't given.
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@end itemize
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The option-processing script will usually declare @var{var} in
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@file{options.c} and leave it to be zero-initialized at start-up time.
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You can modify this behavior using @code{VarExists} and @code{Init}.
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@item Var(@var{var}, @var{set})
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The option controls an integer variable @var{var} and is active when
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@var{var} equals @var{set}. The option parser will set @var{var} to
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@var{set} when the positive form of the option is used and @code{!@var{set}}
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when the ``no-'' form is used.
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@var{var} is declared in the same way as for the single-argument form
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described above.
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@item VarExists
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The variable specified by the @code{Var} property already exists.
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No definition should be added to @file{options.c} in response to
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this option record.
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You should use this property only if the variable is declared outside
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@file{options.c}.
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@item Init(@var{value})
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The variable specified by the @code{Var} property should be statically
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initialized to @var{value}.
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@item Mask(@var{name})
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The option is associated with a bit in the @code{target_flags}
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variable (@pxref{Run-time Target}) and is active when that bit is set.
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You may also specify @code{Var} to select a variable other than
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@code{target_flags}.
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The options-processing script will automatically allocate a unique bit
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for the option. If the option is attached to @samp{target_flags},
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the script will set the macro @code{MASK_@var{name}} to the appropriate
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bitmask. It will also declare a @code{TARGET_@var{name}} macro that has
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the value 1 when the option is active and 0 otherwise. If you use @code{Var}
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to attach the option to a different variable, the associated macros are
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called @code{OPTION_MASK_@var{name}} and @code{OPTION_@var{name}} respectively.
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You can disable automatic bit allocation using @code{MaskExists}.
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@item InverseMask(@var{othername})
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@itemx InverseMask(@var{othername}, @var{thisname})
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The option is the inverse of another option that has the
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@code{Mask(@var{othername})} property. If @var{thisname} is given,
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the options-processing script will declare a @code{TARGET_@var{thisname}}
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macro that is 1 when the option is active and 0 otherwise.
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@item MaskExists
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The mask specified by the @code{Mask} property already exists.
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No @code{MASK} or @code{TARGET} definitions should be added to
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@file{options.h} in response to this option record.
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The main purpose of this property is to support synonymous options.
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The first option should use @samp{Mask(@var{name})} and the others
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should use @samp{Mask(@var{name}) MaskExists}.
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@item Report
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The state of the option should be printed by @option{-fverbose-asm}.
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@item Undocumented
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The option is deliberately missing documentation and should not
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be included in the @option{--help} output.
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@item Condition(@var{cond})
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The option should only be accepted if preprocessor condition
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@var{cond} is true. Note that any C declarations associated with the
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option will be present even if @var{cond} is false; @var{cond} simply
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controls whether the option is accepted and whether it is printed in
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the @option{--help} output.
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@end table
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