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From: Junwang Zhao <zhjwpku@gmail.com>
Date: Thu, 26 Feb 2026 19:04:24 +0800
Message-ID: <CAEG8a3KqfVfHbHN5ZqNBmEhf9AkiccvP9GRtQRTYWad2yzWvOA@mail.gmail.com>
Subject: Re: guc: make dereference style consistent in check_backtrace_functions
To: Chao Li <li.evan.chao@gmail.com>
Cc: zhanghu <kongbaik228@gmail.com>, pgsql-hackers@lists.postgresql.org
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On Thu, Feb 26, 2026 at 5:21=E2=80=AFPM Chao Li <li.evan.chao@gmail.com> wr=
ote:
>
>
>
> > On Feb 26, 2026, at 15:03, zhanghu <kongbaik228@gmail.com> wrote:
> >
> > Hi,
> >
> > In check_backtrace_functions(), most accesses to the input string follo=
w the pattern (*newval)[i]. However, the empty-string check is currently wr=
itten as:
> >
> > if (*newval[0] =3D=3D '\0')
> >
> > While functionally correct due to how the compiler handles the address-=
of-address context here, this form is semantically misleading. It relies on=
 implicit operator precedence rather than explicit intent.
> >
> > The attached patch rewrites it as:
> >
> > if ((*newval)[0] =3D=3D '\0')
> >
> > This change ensures semantic clarity and maintains a consistent derefer=
encing style throughout the function. No functional changes are introduced.
> >
> > Regards,
> > Zhang Hu
> > <v1-0001-guc-make-dereference-style-consistent-in-check_ba.patch>
>
> This is an interesting find.
>
> [] has higher precedence than *, so:
>
>  - (*newval)[i] means to get the first string, then get the char at posit=
ion i
>  - *newval[i] means to get the array element at position i, then get the =
first char
>
> When i is 0, (*newval)[0] and *newval[0] happen to yield the same result,=
 so this isn't a functional bug.
>
> However, in the GUC context, newval is a point to a string rather than a =
two-dimension char array, *newval[i] is meaningless,  so +1 for fixing this=
 to improve readability.

+1
The double pointer indicates an output parameter, the commit
message should be adjusted though.

>
> Best regards,
> --
> Chao Li (Evan)
> HighGo Software Co., Ltd.
> https://www.highgo.com/
>
>
>
>
>
>


--=20
Regards
Junwang Zhao