WordPress at a glance
action is not described

gc_cache action-hook . WPSCache 1.0

Usage

add_action( 'gc_cache', 'action_function_name_925', 10, 2 );
function action_function_name_925( $string, $permalink ){
	// action...
}
$string
-
$permalink
-

Where the hook is called

wp_cache_post_id_gc()
gc_cache
wp_cache_post_change()
gc_cache
wp-super-cache/wp-cache-phase2.php 2943
do_action( 'gc_cache', 'prune', $permalink );
wp-super-cache/wp-cache-phase2.php 2948
do_action( 'gc_cache', 'prune', 'page/' );
wp-super-cache/wp-cache-phase2.php 2952
do_action( 'gc_cache', 'prune', $permalink );
wp-super-cache/wp-cache-phase2.php 3021
do_action( 'gc_cache', 'prune', 'homepage' );
wp-super-cache/wp-cache-phase2.php 3034
do_action( 'gc_cache', 'prune', $permalink );
wp-super-cache/wp-cache-phase2.php 3070
do_action( 'gc_cache', 'rebuild', $permalink );
wp-super-cache/wp-cache-phase2.php 3080
do_action( 'gc_cache', 'rebuild', trailingslashit( $meta[ 'uri' ] ) );

Where in WP core the hook is used WP Super Cache

wp-super-cache/plugins/domain-mapping.php 57
add_action( 'gc_cache', 'domain_mapping_gc_cache', 10, 2 );
wp-super-cache/wp-cache.php 4206
add_action( 'gc_cache', 'wpsc_feed_update', 10, 2 );