This reference provides information on the correct formatting of link.xml
files, including valid XML elements and attributes and usage examples.
The following XML elements are supported in link.xml files:
Element | Description |
---|---|
<linker></linker> |
Must be used in all link.xml files as the outermost element enclosing all other elements. |
<assembly></assembly> |
Declare code preservation annotations specific to an assembly. |
<type></type> |
Declare code preservation annotations specific to a type. |
<field></field> |
Declare code preservation annotations specific to a field. |
<method></method> |
Declare code preservation annotations specific to a method. |
<property></property> |
Declare code preservation annotations specific to a property. |
<event></event> |
Declare code preservation annotations specific to an event. |
For example usages of all these elements, refer to Usage examples.
Attribute | Description |
---|---|
accessors |
Apply to a <property> element to specify which of the property’s accessor methods to preserve. |
feature |
Exclude preservations for features that aren’t supported based on the settings for the current build. For more information and a usage example, refer to Feature exclusions. |
fullname |
Identify a code element by name including its parent assembly name as a prefix. Use fullname whenever name alone could be ambiguous. |
ignoreIfMissing |
Apply to an <assembly> element to declare preservations for an assembly that doesn’t exist during all Player builds. For example usage, refer to Ignore a missing assembly. |
ignoreIfUnreferenced |
Apply to an <assembly> element to preserve the entities in an assembly only if at least one of its members is referenced by another assembly. For example usage, refer to Ignore an unreferenced assembly. |
name |
Identify a code element by name only, without the parent assembly as a prefix. If the assembly name has already been specified with fullname in a parent XML element, child XML elements can identify the code element by name alone. |
preserve |
Specify the level of code elements to preserve from stripping. |
signature |
Identify a code element by its signature. A method signature consists of the return type, name, and parameters. A field, property, or event signature consists of the type and name. For example usage, refer to Usage examples. |
windowsruntime |
Must be added to the <assembly> element in the link.xml file whenever you define preservations for a Windows Runtime Metadata (.winmd) assembly. For example usage, refer to Windows Runtime Metadata assembly. |
For example usages of all these attributes, refer to Usage examples.
The following examples demonstrate valid usage of the supported XML elements and attributes.
The following examples illustrate the different ways that you can declare the root types of a project’s assemblies using a link.xml
file:
<linker>
<!--Preserve types and members in an assembly-->
<assembly fullname="AssemblyName">
<!--Preserve an entire type-->
<type fullname="AssemblyName.TypeName" preserve="all"/>
<!--No "preserve" attribute and no members specified means preserve all members-->
<type fullname="AssemblyName.TypeName"/>
<!--Preserve all fields on a type-->
<type fullname="AssemblyName.TypeName" preserve="fields"/>
<!--Preserve all methods on a type-->
<type fullname="AssemblyName.TypeName" preserve="methods"/>
<!--Preserve the type only-->
<type fullname="AssemblyName.TypeName" preserve="nothing"/>
<!--Preserving only specific members of a type-->
<type fullname="AssemblyName.TypeName">
<!--Fields-->
<field signature="System.Int32 FieldName" />
<!--Preserve a field by name rather than signature-->
<field name="FieldName" />
<!--Methods-->
<method signature="System.Void MethodName()" />
<!--Preserve a method with parameters-->
<method signature="System.Void MethodName(System.Int32,System.String)" />
<!--Preserve a method by name rather than signature-->
<method name="MethodName" />
<!--Properties-->
<!--Preserve a property, its backing field (if present),
getter, and setter methods-->
<property signature="System.Int32 PropertyName" />
<property signature="System.Int32 PropertyName" accessors="all" />
<!--Preserve a property, its backing field (if present), and getter method-->
<property signature="System.Int32 PropertyName" accessors="get" />
<!--Preserve a property, its backing field (if present), and setter method-->
<property signature="System.Int32 PropertyName" accessors="set" />
<!--Preserve a property by name rather than signature-->
<property name="PropertyName" />
<!--Events-->
<!--Preserve an event, its backing field (if present), add, and remove methods-->
<event signature="System.EventHandler EventName" />
<!--Preserve an event by name rather than signature-->
<event name="EventName" />
</type>
</assembly>
</linker>
The following example shows how you can declare entire assemblies:
<!--Preserve an entire assembly-->
<assembly fullname="AssemblyName" preserve="all"/>
<!--No "preserve" attribute and no types specified means preserve all-->
<assembly fullname="AssemblyName"/>
<!--Fully qualified assembly name-->
<assembly fullname="AssemblyName, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null">
<type fullname="AssemblyName.Foo" preserve="all"/>
</assembly>
<!--Force an assembly to be processed for roots but don't explicitly preserve anything in particular. Useful when the assembly isn't referenced.-->
<assembly fullname="AssemblyName" preserve="nothing"/>
The following example shows how to preserve either nested or generic types:
<!--Examples with generics-->
<type fullname="AssemblyName.G`1">
<!--Preserve a field with generics in the signature-->
<field signature="System.Collections.Generic.List`1<System.Int32> FieldName" />
<field signature="System.Collections.Generic.List`1<T> FieldName" />
<!--Preserve a method with generics in the signature-->
<method signature="System.Void MethodName(System.Collections.Generic.List`1<System.Int32>)" />
<!--Preserve an event with generics in the signature-->
<event signature="System.EventHandler`1<System.EventArgs> EventName" />
</type>
<!--Preserve a nested type-->
<type fullname="AssemblyName.H/Nested" preserve="all"/>
<!--Preserve all fields of a type if the type is used. If the type isn't used, it will be removed-->
<type fullname="AssemblyName.I" preserve="fields" required="0"/>
<!--Preserve all methods of a type if the type is used. If the type isn't used, it will be removed-->
<type fullname="AssemblyName.J" preserve="methods" required="0"/>
<!--Preserve all types in a namespace-->
<type fullname="AssemblyName.SomeNamespace*" />
<!--Preserve all types with a common prefix in their name-->
<type fullname="Prefix*" />
Use the ignoreIfMissing
attribute on the <assembly>
element if you need to declare preservations for an assembly that doesn’t exist during all Player builds:
<linker>
<assembly fullname="Foo" ignoreIfMissing="1">
<type name="TypeName"/>
</assembly>
</linker>
Use the ignoreIfUnreferenced
attribute on the <assembly>
element to preserve the entities in an assembly only when at least one type is referenced in another assembly:
<linker>
<assembly fullname="Bar" ignoreIfUnreferenced="1">
<type name="TypeName"/>
</assembly>
</linker>
You must use the windowsruntime
attribute on the <assembly>
element whenever you define preservations for a Windows Runtime Metadata (.winmd) assembly:
<linker>
<assembly fullname="Windows" windowsruntime="true">
<type name="TypeName"/>
</assembly>
</linker>
The mscorlib.xml
file embedded in mscorlib.dll
uses this attribute, but you can use it in any link.xml
file when appropriate.
At the High stripping level, the Unity linker excludes preservations for features that aren’t supported based on the settings for the current build:
remoting
— Excluded when targeting the IL2CPPA Unity-developed scripting back-end which you can use as an alternative to Mono when building projects for some platforms. More infosre
— Excluded when targeting the IL2CPP scripting backend.com
— Excluded when targeting platforms that don’t support COM.For example, the following link.xml
file preserves one method of a type on platforms that support COM, and one method on all platforms:
<linker>
<assembly fullname="Foo">
<type fullname="Type1">
<!--Preserve FeatureOne on platforms that support COM-->
<method signature="System.Void FeatureOne()" feature="com"/>
<!--Preserve FeatureTwo on all platforms-->
<method signature="System.Void FeatureTwo()"/>
</type>
</assembly>
</linker>
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