Anonymous namespace in header files

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3.50/5 (2 votes)

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Hi,

I was wondering on peoples opinion's / best practices whether you think it is a good or bad thing to have a anonymous namespace in a header file.

Thanks for your input.

Posted 4-Jul-11 10:54am

bob_bobber2005

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2 solutions

Solution 1

It depends on the application. Anonymous namespaces, like many things in C++, are good tools if used well, and bad if used badly. Why would you decide to use an anonymous namespace ? Do you want to hide the contents ? The point of an anonymous namespace is that it can't be discovered and therefore cannot be used, as far as I recall.

Posted 4-Jul-11 13:28pm

Christian Graus

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ThatsAlok 5-Jul-11 8:19am

agreed!

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Philippe Mori · Accepted Answer · 2011-07-04T15:25:00

Solution 2

I would say that anonymous namespace in header file are generally evil.

In practice an unnammed namespace would generate a namespace with a unique compiler generated name for each source file.

Thus each source file that would include that header would see a different definition which is probably not what you intend.

As a general use, uses them only in source file if you want to avoid symbols to be visible to other source files.

Posted 4-Jul-11 15:25pm

Philippe Mori

Updated 5-Jul-11 1:23am

v2

Comments

Christian Graus 4-Jul-11 21:28pm

I was wondering if he was thinking of a case where all the source code is in the header file ?

Sergey Alexandrovich Kryukov 4-Jul-11 22:21pm

I basically agree, my 5. Not using name spaces probably may fit the purpose when trying to quickly write a small application, such as a code sample for CodeProject.
--SA

bob_bobber2005 5-Jul-11 14:51pm

Hi,

Thanks for your input. It was not me who wrote the class with a anonymous namespace in the header file (it's from source code at work on a very large system and I've only been there 2 weeks). I raised this question as I have not seen it before and so wanted other developers opinions about it.

Thanks.