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From: Florian Weimer <fw@deneb.enyo.de>
To: =?utf-8?B?5a2Z5LiW6b6Z?= sunshilong <sunshilong369@gmail.com>
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Subject: Re: How to verify some macro is available for a specific version of
 GLIBC that is installed on my PC?
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* =E5=AD=99=E4=B8=96=E9=BE=99 sunshilong:

> Thank you for your clarification.
>
>>You can read the glibc source code.

> No other methods? Maybe it's meaningful(or faster) when verifying when
> a specific macro is first introduced then reading each version source
> code.

The Linux man-pages project provides this information in some special
cases.  But I do not know a source of this information for the general
case.

>
>>__MALLOC_HOOK_VOLATILE is an internal macro and should only be used
>>within glibc itself.  It can go away at any time.

> Do you indicate that the said macro could not be found in the
> headers of GLIBC?

Some of the headers contain internal implementation macros, identified
by two leading underscores (__).  Thet are not supposed to be used
outside of glibc, but are included in installed headers for technical
reasons.