Re: [PATCH] Suppress Clang 3.9 warnings

From: Aleksander Alekseev <a(dot)alekseev(at)postgrespro(dot)ru>
To: Noah Misch <noah(at)leadboat(dot)com>
Cc: David Steele <david(at)pgmasters(dot)net>, PostgreSQL Developers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: [PATCH] Suppress Clang 3.9 warnings
Date: 2017-03-15 09:04:11
Message-ID: 20170315090410.GA25568@e733.localdomain
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Hi Hoah.

Thanks a lot for a reply!

> This is wrong on platforms that do have strlcpy() in libc.

If it no too much trouble could you please explain what will happen
on such platforms? On what platform did you check it? I'm sure it
fixable. And I got a strong feeling that "wrong" could be a bit exaggerated.

> If I recall correctly, you can suppress the warnings in your own build by
> adding "ac_cv_func_strlcpy=no ac_cv_have_decl_strlcpy=no ac_cv_func_strlcat=no
> ac_cv_have_decl_strlcat=no" to the "configure" command line.

It's not exactly what I would call a solution. For instance on FreeBSD
Clang is a default compiler and many users build a software from source
code (FreeBSD ports). For some reason I doubt that many of them know
about these flags.

On Wed, Mar 15, 2017 at 02:25:38AM +0000, Noah Misch wrote:
> On Mon, Mar 13, 2017 at 06:35:53PM +0300, Aleksander Alekseev wrote:
> > --- a/src/include/port.h
> > +++ b/src/include/port.h
> > @@ -395,11 +395,22 @@ extern double rint(double x);
> > extern int inet_aton(const char *cp, struct in_addr * addr);
> > #endif
> >
> > -#if !HAVE_DECL_STRLCAT
> > +/*
> > + * Unfortunately in case of strlcat and strlcpy we can't trust tests
> > + * executed by Autotools if Clang > 3.6 is used. Clang manages to compile
> > + * a program that shouldn't compile which causes wrong values of
> > + * HAVE_DECL_STRLCAT and HAVE_DECL_STRLCPY. More details could be found here:
> > + *
> > + * http://lists.llvm.org/pipermail/cfe-dev/2016-March/048126.html
> > + *
> > + * This is no doubt a dirty hack but apparently alternative solutions are
> > + * not much better.
> > + */
> > +#if !HAVE_DECL_STRLCAT || defined(__clang__)
> > extern size_t strlcat(char *dst, const char *src, size_t siz);
> > #endif
> >
> > -#if !HAVE_DECL_STRLCPY
> > +#if !HAVE_DECL_STRLCPY || defined(__clang__)
> > extern size_t strlcpy(char *dst, const char *src, size_t siz);
> > #endif
>
> This is wrong on platforms that do have strlcpy() in libc.
>
> If I recall correctly, you can suppress the warnings in your own build by
> adding "ac_cv_func_strlcpy=no ac_cv_have_decl_strlcpy=no ac_cv_func_strlcat=no
> ac_cv_have_decl_strlcat=no" to the "configure" command line.

--
Best regards,
Aleksander Alekseev

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