[Cfp-interest 1507] Fw: Re: Question about strfromd in glibc

[Rajan Bhakta]

So it seems glibc does do the right thing (null terminate) and the web 
page was wrong.

Regards,

Rajan Bhakta
z/OS XL C/C++ Compiler Technical Architect
ISO C Standards Representative for Canada, PL22.11 Chair (USA)
C Compiler Development
Contact: rbhakta at us.ibm.com, Rajan Bhakta/Houston/IBM
----- Forwarded by Rajan Bhakta/Houston/IBM on 02/19/2020 08:04 PM -----

From:   Joseph Myers <joseph at codesourcery.com>
To:     Rajan Bhakta <rbhakta at us.ibm.com>
Date:   02/19/2020 04:20 PM
Subject:        [EXTERNAL] Re: Question about strfromd in glibc



On Wed, 19 Feb 2020, Rajan Bhakta wrote:

> Hi Joseph,
> 
> Looking at 
https://urldefense.proofpoint.com/v2/url?u=http-3A__man7.org_linux_man-2Dpages_man3_strfromd.3.html&d=DwIBAg&c=jf_iaSHvJObTbx-siA1ZOg&r=MPb4GyWs7nd-w3OlFPs29W1dB3gHMdsdghhjcQMf428&m=hxILeDqVdlHoUYoqw9PFLsLVMma87WGosQbgEvRpXSk&s=x0XHdZsq7q89h2YP2NIyK2LWwaZVVoHFRuiHfxw4e34&e= 
, it seems 
> to say you could end up with strings that are not null terminated. But 
> from the C standard draft (N2454 for example) it says that the strings 
are 
> always null terminated and only that you may get incomplete (truncation 
> from the right) if 'n' is too small (yet still null terminated). Was 
this 
> an intentional decision or am I understanding the documentation wrong?

The strfrom functions are equivalent to particular calls to snprintf, so 
they should always null-terminate their output (when a nonzero size is 
specified).  The manpages are not official glibc documentation.

-- 
Joseph S. Myers
joseph at codesourcery.com




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