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| <a name="Marking-Roots-for-the-Garbage-Collector"></a> |
| <h3 class="section">22.4 Marking Roots for the Garbage Collector</h3> |
| <a name="index-roots_002c-marking"></a> |
| <a name="index-marking-roots"></a> |
| |
| <p>In addition to keeping track of types, the type machinery also locates |
| the global variables (<em>roots</em>) that the garbage collector starts |
| at. Roots must be declared using one of the following syntaxes: |
| </p> |
| <ul> |
| <li> <code>extern GTY(([<var>options</var>])) <var>type</var> <var>name</var>;</code> |
| </li><li> <code>static GTY(([<var>options</var>])) <var>type</var> <var>name</var>;</code> |
| </li></ul> |
| <p>The syntax |
| </p><ul> |
| <li> <code>GTY(([<var>options</var>])) <var>type</var> <var>name</var>;</code> |
| </li></ul> |
| <p>is <em>not</em> accepted. There should be an <code>extern</code> declaration |
| of such a variable in a header somewhere—mark that, not the |
| definition. Or, if the variable is only used in one file, make it |
| <code>static</code>. |
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