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8.2 Option properties

The second field of an option record can specify any of the following properties. When an option takes an argument, it is enclosed in parentheses following the option property name. The parser that handles option files is quite simplistic, and will be tricked by any nested parentheses within the argument text itself; in this case, the entire option argument can be wrapped in curly braces within the parentheses to demarcate it, e.g.:


The option is available for all languages and targets.


The option is available for all languages but is target-specific.


The option is handled by the compiler driver using code not shared with the compilers proper (cc1 etc.).


The option is available when compiling for the given language.

It is possible to specify several different languages for the same option. Each language must have been declared by an earlier Language record. See Option file format.


The option is only handled by the compilers proper (cc1 etc.) and should not be accepted by the driver.


The option does not have a “no-” form. All options beginning with “f”, “W” or “m” are assumed to have a “no-” form unless this property is used.


The option will turn off another option othername, which is the option name with the leading “-” removed. This chain action will propagate through the Negative property of the option to be turned off.

As a consequence, if you have a group of mutually-exclusive options, their Negative properties should form a circular chain. For example, if options -a, -b and -c are mutually exclusive, their respective Negative properties should be ‘Negative(b)’, ‘Negative(c)’ and ‘Negative(a)’.


The option takes a mandatory argument. Joined indicates that the option and argument can be included in the same argv entry (as with -mflush-func=name, for example). Separate indicates that the option and argument can be separate argv entries (as with -o). An option is allowed to have both of these properties.


The option takes an optional argument. If the argument is given, it will be part of the same argv entry as the option itself.

This property cannot be used alongside Joined or Separate.


For an option marked Joined or Separate, the message message will be used as an error message if the mandatory argument is missing; for options without MissingArgError, a generic error message is used. message should contain a single ‘%qs’ format, which will be used to format the name of the option passed.


For an option marked Separate, indicate that it takes n arguments. The default is 1.


The option’s argument is a non-negative integer. The option parser will check and convert the argument before passing it to the relevant option handler. UInteger should also be used on options like -falign-loops where both -falign-loops and -falign-loops=n are supported to make sure the saved options are given a full integer.


The option’s argument should be converted to lowercase as part of putting it in canonical form, and before comparing with the strings indicated by any Enum property.


For an option marked Separate, the option only takes an argument in the compiler proper, not in the driver. This is for compatibility with existing options that are used both directly and via -Wp,; new options should not have this property.


The state of this option should be stored in variable var (actually a macro for global_options.x_var). The way that the state is stored depends on the type of option:

The option-processing script will usually zero-initialize var. You can modify this behavior using Init.

Var(var, set)

The option controls an integer variable var and is active when var equals set. The option parser will set var to set when the positive form of the option is used and !set when the “no-” form is used.

var is declared in the same way as for the single-argument form described above.


The variable specified by the Var property should be statically initialized to value. If more than one option using the same variable specifies Init, all must specify the same initializer.


The option is associated with a bit in the target_flags variable (see Run-time Target) and is active when that bit is set. You may also specify Var to select a variable other than target_flags.

The options-processing script will automatically allocate a unique bit for the option. If the option is attached to ‘target_flags’, the script will set the macro MASK_name to the appropriate bitmask. It will also declare a TARGET_name macro that has the value 1 when the option is active and 0 otherwise. If you use Var to attach the option to a different variable, the bitmask macro with be called OPTION_MASK_name.

InverseMask(othername, thisname)

The option is the inverse of another option that has the Mask(othername) property. If thisname is given, the options-processing script will declare a TARGET_thisname macro that is 1 when the option is active and 0 otherwise.


The option’s argument is a string from the set of strings associated with the corresponding ‘Enum’ record. The string is checked and converted to the integer specified in the corresponding ‘EnumValue’ record before being passed to option handlers.


The option should be stored in a vector, specified with Var, for later processing.

Alias(opt, arg)
Alias(opt, posarg, negarg)

The option is an alias for -opt (or the negative form of that option, depending on NegativeAlias). In the first form, any argument passed to the alias is considered to be passed to -opt, and -opt is considered to be negated if the alias is used in negated form. In the second form, the alias may not be negated or have an argument, and posarg is considered to be passed as an argument to -opt. In the third form, the alias may not have an argument, if the alias is used in the positive form then posarg is considered to be passed to -opt, and if the alias is used in the negative form then negarg is considered to be passed to -opt.

Aliases should not specify Var or Mask or UInteger. Aliases should normally specify the same languages as the target of the alias; the flags on the target will be used to determine any diagnostic for use of an option for the wrong language, while those on the alias will be used to identify what command-line text is the option and what text is any argument to that option.

When an Alias definition is used for an option, driver specs do not need to handle it and no ‘OPT_’ enumeration value is defined for it; only the canonical form of the option will be seen in those places.


For an option marked with Alias(opt), the option is considered to be an alias for the positive form of -opt if negated and for the negative form of -opt if not negated. NegativeAlias may not be used with the forms of Alias taking more than one argument.


This option is ignored apart from printing any warning specified using Warn. The option will not be seen by specs and no ‘OPT_’ enumeration value is defined for it.


For an option marked with Joined, Separate and Alias, the option only acts as an alias when passed a separate argument; with a joined argument it acts as a normal option, with an ‘OPT_’ enumeration value. This is for compatibility with the Java -d option and should not be used for new options.


If this option is used, output the warning message. message is a format string, either taking a single operand with a ‘%qs’ format which is the option name, or not taking any operands, which is passed to the ‘warning’ function. If an alias is marked Warn, the target of the alias must not also be marked Warn.


The state of the option should be printed by -fverbose-asm.


This is a warning option and should be shown as such in --help output. This flag does not currently affect anything other than --help.


This is an optimization option. It should be shown as such in --help output, and any associated variable named using Var should be saved and restored when the optimization level is changed with optimize attributes.


This is an option that can be overridden on a per-function basis. Optimization implies PerFunction, but options that do not affect executable code generation may use this flag instead, so that the option is not taken into account in ways that might affect executable code generation.


The option is deliberately missing documentation and should not be included in the --help output.


The option should only be accepted if preprocessor condition cond is true. Note that any C declarations associated with the option will be present even if cond is false; cond simply controls whether the option is accepted and whether it is printed in the --help output.


Build the cl_target_option structure to hold a copy of the option, add the functions cl_target_option_save and cl_target_option_restore to save and restore the options.


The option may also be set by a combined option such as -ffast-math. This causes the gcc_options struct to have a field frontend_set_name, where name is the name of the field holding the value of this option (without the leading x_). This gives the front end a way to indicate that the value has been set explicitly and should not be changed by the combined option. For example, some front ends use this to prevent -ffast-math and -fno-fast-math from changing the value of -fmath-errno for languages that do not use errno.

EnabledBy(opt || opt2)
EnabledBy(opt && opt2)

If not explicitly set, the option is set to the value of -opt; multiple options can be given, separated by ||. The third form using && specifies that the option is only set if both opt and opt2 are set. The options opt and opt2 must have the Common property; otherwise, use LangEnabledBy.

LangEnabledBy(language, opt)
LangEnabledBy(language, opt, posarg, negarg)

When compiling for the given language, the option is set to the value of -opt, if not explicitly set. opt can be also a list of || separated options. In the second form, if opt is used in the positive form then posarg is considered to be passed to the option, and if opt is used in the negative form then negarg is considered to be passed to the option. It is possible to specify several different languages. Each language must have been declared by an earlier Language record. See Option file format.


The option is omitted from the producer string written by -grecord-gcc-switches.


Even if this is a target option, this option will not be recorded / compared to determine if a precompiled header file matches.


The state of this option should be kept in sync with the preprocessor option var. If this property is set, then properties Var and Init must be set as well.


This warning option corresponds to cpplib.h warning reason code CPP_W_Enum. This should only be used for warning options of the C-family front-ends.

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