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Re: The meaning of double-underscore symbols

From: Max Bowsher <maxb_at_ukf.net>
Date: 2005-10-04 17:30:25 CEST

Joshua Varner wrote:
> On 10/4/05, Max Bowsher <maxb@ukf.net> wrote:
>> I don't believe we've ever defined *exactly* what the significance of a
>> double-underscore symbol name is.
>> Two of definitions I've heard of are:
>>
>> (a) anything that should not be used by users, but can we used at will
>> internally by the Subversion libraries.
>>
>> (b) symbols that should have visibility only to the library that they are
>> defined in, and should not be used *anywhere* outside that library.
>>
>>
>> The double-underscore symbols which do not meet the strictest definition
>> are:
>>
>> svn_error__locate: used almost everywhere
>> svn_sort__hash: used by libsvn_client, mod_dav_svn, and svn
>> svn_{fs,ra}_foo__init: linked into the loader libs
>> svn_txdelta__apply_instructions, svn_txdelta__compose_windows: used by
>> the
>> fs backends
>>
>>
>> If anyone knows of an official definition of what svn_foo__bar means,
>> please tell me, otherwise, opinions and thoughts welcome, so we can craft
>> an official definition.
>>
>>
> Are you saying this section from
> http://subversion.tigris.org/hacking.html#other-conventions
> is incomplete or that is just hard to find? I believe this implies b.
>
> QUOTE
> Signify internal variables by two underscores after the prefix. That
> is, when a symbol must (for technical reasons) reside in the global
> namespace despite not being part of a published interface, then use
> two underscores following the module prefix. For example:
>
> svn_fs_get_rev_prop () /* Part of published API. */
> svn_fs__parse_props () /* For internal use only. */
> END QUOTE

It is unclear exactly what is allowed to make use of these symbols - only
the library containing that symbol, or any code within the subversion
project.

Max.

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Received on Tue Oct 4 17:32:38 2005

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