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List:       mingw-users
Subject:    Re: [Mingw-users] GCC 6.3.0 warns about vsnprintf
From:       Keith Marshall via MinGW-users <mingw-users () lists ! sourceforge ! net>
Date:       2017-09-09 9:39:16
Message-ID: 59B3B6C4.2010709 () users ! sourceforge ! net
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On 09/09/17 08:09, Eli Zaretskii wrote:
> > Date: Fri, 8 Sep 2017 21:02:36 +0100
> > From: Keith Marshall via MinGW-users <mingw-users@lists.sourceforge.net>
> > 
> > > But if vsnprintf is already declared as conforming to mingw_printf
> > > rules, why does GCC "suggest it to be a possible candidate" for those
> > > very rules?  Are you saying that the warning disregards the existing
> > > format attributes?
> > 
> > I think it is suggesting that your foo() is a candidate for declaration 
> > with that attribute, because it passes its own arguments to vsnprintf(), 
> > which is explicitly declared thus; certainly, that particular suggestion 
> > disappears, when foo() is so declared.
> 
> I see.  And why do you think is that warning emitted only about
> vsnprintf, but not about the other functions of the printf family?

I don't know, but as a purely speculative guess: of the entire standard 
printf() function family, MSVCRT.DLL provides all but snprintf(), and 
vsnprintf(), (instead providing non-standard variants with their names 
prefixed by an underscore).  Thus, for this pair specifically, any call 
will always resolve to a MinGW implementation, which conforms to our new 
mingw_printf format interpretation rules, whereas a call to any other printf() family \
function, by default, resolves to Microsoft's MSVCRT.DLL  implementation, which \
conforms to ms_printf format rules.  Perhaps GCC  becomes confused, when any function \
in the printf() family explicitly  does not comply with its blind (and IMO \
ill-advised) assumption that,  for any MS-Windows target, it *must* exhibit behaviour \
as defined by  ms_printf format conventions.

- -- 
Regards,
Keith.

Public key available from keys.gnupg.net
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