From: | Andres Freund <andres(at)anarazel(dot)de> |
---|---|
To: | Noah Misch <noah(at)leadboat(dot)com> |
Cc: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-committers(at)postgresql(dot)org |
Subject: | Re: Re: pgsql: Convert contrib/seg's bool-returning SQL functions to V1 call co |
Date: | 2016-04-27 02:44:15 |
Message-ID: | 20160427024415.6mv2dtyifpkv7g6v@alap3.anarazel.de |
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On 2016-04-26 22:38:28 -0400, Noah Misch wrote:
> On Fri, Apr 22, 2016 at 03:54:48PM +0000, Tom Lane wrote:
> > Convert contrib/seg's bool-returning SQL functions to V1 call convention.
> >
> > It appears that we can no longer get away with using V0 call convention
> > for bool-returning functions in newer versions of MSVC. The compiler
> > seems to generate code that doesn't clear the higher-order bits of the
> > result register, causing the bool result Datum to often read as "true"
> > when "false" was intended. This is not very surprising, since the
> > function thinks it's returning a bool-width result but fmgr_oldstyle
> > assumes that V0 functions return "char *"; what's surprising is that
> > that hack worked for so long on so many platforms.
>
> Does this warrant a change to the "Section 2" comment of postgres.h,
> explaining that its precautions no longer suffice everywhere?
I don't understand why we don't just drop V0. It makes debugging harder,
exploitation easier (call arbitrary functions), and really has no
features making it desirable.
Andres
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