Horton

Re: GCC 8 warnings

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Peter Eisentraut <peter.eisentraut@2ndquadrant.com>, Devrim Gündüz <devrim@gunduz.org>, pgsql-hackers <pgsql-hackers@lists.postgresql.org>
Date: 2018-06-16T18:52:18Z
Lists: pgsql-hackers 
Hi,

On 2018-06-16 13:29:55 -0400, Tom Lane wrote:
> I propose the attached patch to disable these warnings if the compiler
> knows the switch for them.  I did not turn them off for CXX though;
> anyone think there's a need to?

No, not for now.  I don't think it's likely that the amount of C++ will
grow significantly anytime soon. And it seems unlikely that the llvm
interfacing code will use C stringops.  Not that I think it'd hurt much
to add it.


> Probably all of this ought to be back-patched as applicable, since
> people will doubtless try to compile back branches with gcc 8.

Yea, It's already pretty annoying.


> diff --git a/configure.in b/configure.in
> index 862d8b128d..dae29a4ab1 100644
> --- a/configure.in
> +++ b/configure.in
> @@ -502,6 +502,15 @@ if test "$GCC" = yes -a "$ICC" = no; then
>    if test -n "$NOT_THE_CFLAGS"; then
>      CFLAGS="$CFLAGS -Wno-unused-command-line-argument"
>    fi
> +  # Similarly disable useless truncation warnings from gcc 8+
> +  PGAC_PROG_CC_VAR_OPT(NOT_THE_CFLAGS, [-Wformat-truncation])
> +  if test -n "$NOT_THE_CFLAGS"; then
> +    CFLAGS="$CFLAGS -Wno-format-truncation"
> +  fi
> +  PGAC_PROG_CC_VAR_OPT(NOT_THE_CFLAGS, [-Wstringop-truncation])
> +  if test -n "$NOT_THE_CFLAGS"; then
> +    CFLAGS="$CFLAGS -Wno-stringop-truncation"
> +  fi

I've not had a lot of coffee yet this morning, but couldn't there be an
issue where a compiler supported one of these flags? Because
NOT_THE_CFLAGS is reused, it'd trigger lateron as well, right?  Seems to
me we'd need to reset it.

Greetings,

Andres Freund

Commits

  1. Use -Wno-format-truncation and -Wno-stringop-truncation, if available.

  2. Avoid unnecessary use of strncpy in a couple of places in ecpg.

  3. Use snprintf not sprintf in pg_waldump's timestamptz_to_str.