Description:
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If the configuration apc.file_update_protection is set (default 2 seconds) you can't use the function apc_delete_file after you updated a file.

The problem is, that the internal function apc_cache_make_file_key checks for configuration apc.file_update_protection. So the functionality of this internal function depends on an unnecessary configuration option.

Expected result:
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Delete cache entry for file, which was generated shortly before.

Actual result:
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Cache not cleared and a warning ommited: "PHP Warning: apc_delete_file(): Could not stat file ..." which is false.