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7.1 Option file format ¶

Option files are a simple list of records in which each field occupiesits own line and in which the records themselves are separated byblank lines. Comments may appear on their own line anywhere withinthe file and are preceded by semicolons. Whitespace is allowed beforethe semicolon.

The files can contain the following types of record:

• A language definition record. These records have two fields: thestring ‘Language’ and the name of the language. Once a languagehas been declared in this way, it can be used as an option property.SeeOption properties.
• A target specific save record to save additional information. Theserecords have two fields: the string ‘TargetSave’, and adeclaration type to go in thecl_target_option structure.
• A variable record to define a variable used to store optioninformation. These records have two fields: the string‘Variable’, and a declaration of the type and name of thevariable, optionally with an initializer (but without any trailing‘;’). These records may be used for variables used for manyoptions where declaring the initializer in a single option definitionrecord, or duplicating it in many records, would be inappropriate, orfor variables set in option handlers rather than referenced byVar properties.
• A variable record to define a variable used to store optioninformation. These records have two fields: the string‘TargetVariable’, and a declaration of the type and name of thevariable, optionally with an initializer (but without any trailing‘;’). ‘TargetVariable’ is a combination of ‘Variable’and ‘TargetSave’ records in that the variable is defined in thegcc_options structure, but these variables are also stored inthecl_target_option structure. The variables are saved in thetarget save code and restored in the target restore code.
• A variable record to record any additional files that theoptions.h file should include. This is useful to provideenumeration or structure definitions needed for target variables.These records have two fields: the string ‘HeaderInclude’ and thename of the include file.
• A variable record to record any additional files that theoptions.cc oroptions-save.cc file should include. Thisis useful to provideinline functions needed for target variables and/or#ifdefsequences to properly set up the initialization. These records havetwo fields: the string ‘SourceInclude’ and the name of theinclude file.
• An enumeration record to define a set of strings that may be used asarguments to an option or options. These records have three fields:the string ‘Enum’, a space-separated list of properties and helptext used to describe the set of strings in--help output.Properties use the same format as option properties; the following arevalid:

  Name(name)

  This property is required;name must be a name (suitable for usein C identifiers) used to identify the set of strings inEnumoption properties.

  Type(type)

  This property is required;type is the C type for variables setby options using this enumeration together withVar.

  UnknownError(message)

  The messagemessage will be used as an error message if theargument is invalid; for enumerations withoutUnknownError, ageneric error message is used.message should contain a single‘%qs’ format, which will be used to format the invalid argument.

• An enumeration value record to define one of the strings in a setgiven in an ‘Enum’ record. These records have two fields: thestring ‘EnumValue’ and a space-separated list of properties.Properties use the same format as option properties; the following arevalid:

  Enum(name)

  This property is required;name says which ‘Enum’ recordthis ‘EnumValue’ record corresponds to.

  String(string)

  This property is required;string is the string option argumentbeing described by this record.

  Value(value)

  This property is required; it says what value (representable asint) should be used for the given string.

  Canonical

  This property is optional. If present, it says the present string isthe canonical one among all those with the given value. Other stringsyielding that value will be mapped to this one so specs do not need tohandle them.

  DriverOnly

  This property is optional. If present, the present string will onlybe accepted by the driver. This is used for cases such as-march=native that are processed by the driver so that‘gcc -v’ shows how the options chosen depended on the system onwhich the compiler was run.

  Set(number)

  This property is optional, required for enumerations used inEnumSet options.number should be decimal number between1 and 64 inclusive and divides the enumeration into a set ofsets of mutually exclusive arguments. Arguments with the samenumber can’t be specified together in the same option, butarguments with differentnumber can.value needs to bechosen such that a mask of allvalue values from the same setnumber bitwise ored doesn’t overlap with masks for other sets.When-foption=arg_from_set1,arg_from_set4 and-fno-option=arg_from_set3 are used, the effect is that previousvalue of theVar will get bits from set 1 and 4 masks cleared,oredValue ofarg_from_set1 andarg_from_set4and then will get bits from set 3 mask cleared.

• An option definition record. These records have the following fields:
  1. the name of the option, with the leading “-” removed
  2. a space-separated list of option properties (seeOption properties)
  3. the help text to use for--help (omitted if the second fieldcontains theUndocumented property).

  By default, all options beginning with “f”, “g”, “W” or “m” areimplicitly assumed to take a “no-” form. This form should not belisted separately. If an option beginning with one of these lettersdoes not have a “no-” form, you can use theRejectNegativeproperty to reject it.

  The help text is automatically line-wrapped before being displayed.Normally the name of the option is printed on the left-hand side ofthe output and the help text is printed on the right. However, if thehelp text contains a tab character, the text to the left of the tab isused instead of the option’s name and the text to the right of thetab forms the help text. This allows you to elaborate on what typeof argument the option takes.

  There is no support for different help texts for different languages.If an option is supported for multiple languages, use a genericdescription that is correct for all of them.

  If an option has multiple option definition records (in differentfront ends’*.opt files, and/orgcc/common.opt, forexample), convention is to not duplicate the help text for each ofthem, but instead put a comment like; documented in common.optin place of the help text for all but one of the multiple optiondefinition records.

• A target mask record. These records have one field of the form‘Mask(x)’. The options-processing script will automaticallyallocate a bit intarget_flags (seeRun-time Target Specification) foreach mask namex and set the macroMASK_x to theappropriate bitmask. It will also declare aTARGET_xmacro that has the value 1 when bitMASK_x is set and0 otherwise.

  They are primarily intended to declare target masks that are notassociated with user options, either because these masks representinternal switches or because the options are not available on allconfigurations and yet the masks always need to be defined.

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