[Bug c/39438] Can't compile a wrapper around strftime with -Werror=format-nonliteral

["manu at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=39438

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

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--- Comment #5 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
Could you produce a complete testcase that (In reply to D. Hugh Redelmeier from
comment #4)
> I have this problem too.  I'm writing a wrapper for strftime.  I get a
> warning on the actual strftime call.  
> 
> warning: format not a string literal, format string not checked
> [-Wformat-nonliteral]
>   strftime(buf, buflen, fmt, t);
> 
> Surely GCC should not that for "fmt" argument has been checked to be a valid
> strftime format at the points where prettynow gets called.  So there is no
> need to whine that it is unchecked.
> 

You should be able to produce a minimal self-contained testcase (the one you
posted doesn't compile). See http://gcc.gnu.org/bugs/minimize.html
The best would be to include only the definitions of the types that you need
and declare as 'extern' library functions that you use to avoid including
headers.

If you can produce another similar example that works with printf, that would
also help.

The second step would be to find out why it works with printf and not with
strftime, but that would require debugging GCC while compiling your (new)
testcases, so saving the first step will make it more likely that someone will
do the second.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=61146

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

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--- Comment #4 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Oleg Endo from comment #0)
> The *FLAGS_FOR_TARGET are required or else they will be set to *FLAGS, which
> will pass -fheinous-gnu-extensions to the SH xgcc when building libgcc etc.
> (PR 25672)

It is funny that Clang has a flag called "heinous-gnu-extensions". I wonder
what other things are enabled by that (what they think are heinous GNU
extensions and why).
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http://gcc.gnu.org/bugzilla/show_bug.cgi?ida144

--- Comment #8 from Rich Felker <bugdal at aerifal dot cx> ---
Further investigation suggests that the real gcc 4.8.2 is not affected; I was
mislead by the fact that Debian is shipping as "gcc-4.8_4.8.2-21" an svn
snapshot that's actually post-4.8.2. So 4.9.0 seems to be the only official
release that's affected.