5.9.10 Attributes

A project (and its packages) may have `attributes' that define the project's properties. Some attributes have values that are strings; others have values that are string lists.

    attribute_declaration ::=
       simple_attribute_declaration | indexed_attribute_declaration
    
    simple_attribute_declaration ::= *for* attribute_designator *use* expression ;
    
    indexed_attribute_declaration ::=
      *for* *<indexed_attribute_>*simple_name ( string_literal) *use* expression ;
    
    attribute_designator ::=
      *<simple_attribute_>*simple_name
      | *<indexed_attribute_>*simple_name ( string_literal )

There are two categories of attributes: `simple attributes' and `indexed attributes'. Each simple attribute has a default value: the empty string (for string attributes) and the empty list (for string list attributes). An attribute declaration defines a new value for an attribute, and overrides the previous value. The syntax of a simple attribute declaration is similar to that of an attribute definition clause in Ada.

Some attributes are indexed. These attributes are mappings whose domain is a set of strings. They are declared one association at a time, by specifying a point in the domain and the corresponding image of the attribute. Like untyped variables and simple attributes, indexed attributes may be declared several times. Each declaration supplies a new value for the attribute, and replaces the previous setting.

Here are some examples of attribute declarations:

    --  simple attributes
    for Object_Dir use "objects";
    for Source_Dirs use ("units", "test/drivers");
    
    --  indexed attributes
    for Body ("main") use "Main.ada";
    for Switches ("main.ada")
        use ("-v", "-gnatv");
    for Switches ("main.ada") use Builder'Switches ("main.ada") & "-g";
    
    --  indexed attributes copy (from package Builder in project Default)
    --  The package name must always be specified, even if it is the current
    --  package.
    for Default_Switches use Default.Builder'Default_Switches;

Attributes references may appear anywhere in expressions, and are used to retrieve the value previously assigned to the attribute. If an attribute has not been set in a given package or project, its value defaults to the empty string or the empty list, with some exceptions.

    attribute_reference ::=
      attribute_prefix ' *<simple_attribute>_*simple_name [ (string_literal) ]
    attribute_prefix ::= *project*
      | *<project_>*simple_name
      | package_identifier
      | *<project_>*simple_name . package_identifier

Examples are:

    <project>'Object_Dir
    Naming'Dot_Replacement
    Imported_Project'Source_Dirs
    Imported_Project.Naming'Casing
    Builder'Default_Switches ("Ada")

The exceptions to the empty defaults are:

• Object_Dir: default is "."
• Exec_Dir: default is 'Object_Dir, that is the value of attribute Object_Dir in the same project, declared or defaulted.
• Source_Dirs: default is (".")

The prefix of an attribute may be:

• project for an attribute of the current project
• The name of an existing package of the current project
• The name of an imported project
• The name of a parent project that is extended by the current project
• An expanded name whose prefix is imported/parent project name, and whose selector is a package name

In the following sections, all predefined attributes are succinctly described, first the project level attributes, that is those attributes that are not in a package, then the attributes in the different packages.

It is possible for different tools to dynamically create new packages with attributes, or new attributes in predefined packages. These attributes are not documented here.

The attributes under Configuration headings are usually found only in configuration project files.

The characteristics of each attribute are indicated as follows:

• `Type of value'

  The value of an attribute may be a single string, indicated by the word "single", or a string list, indicated by the word "list".

• `Read-only'

  When the attribute is read-only, that is when it is not allowed to declare the attribute, this is indicated by the words "read-only".

• `Optional index'

  If it is allowed in the value of the attribute (both single and list) to have an optional index, this is indicated by the words "optional index".

• `Indexed attribute'

  When it is an indexed attribute, this is indicated by the word "indexed".

• `Case-sensitivity of the index'

  For an indexed attribute, if the index is case-insensitive, this is indicated by the words "case-insensitive index".

• `File name index'

  For an indexed attribute, when the index is a file name, this is indicated by the words "file name index". The index may or may not be case-sensitive, depending on the platform.

• `others allowed in index'

  For an indexed attribute, if it is allowed to use `others' as the index, this is indicated by the words "others allowed".

  When `others' is used as the index of an indexed attribute, the value of the attribute indexed by `others' is used when no other index would apply.

• Project Level Attributes
• Package Binder Attributes
• Package Builder Attributes
• Package Clean Attributes
• Package Compiler Attributes
• Package Cross_Reference Attributes
• Package Finder Attributes
• Package gnatls Attributes
• Package IDE Attributes
• Package Install Attributes
• Package Linker Attributes
• Package Naming Attributes
• Package Remote Attributes
• Package Stack Attributes
• Package Synchronize Attributes