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Subject: Re: guc: make dereference style consistent in
 check_backtrace_functions
From: Chao Li <li.evan.chao@gmail.com>
In-Reply-To: <CAB5m2QssN6UO+ckr6ZCcV0A71mKUB6WdiTw1nHo43v4DTW1Dfg@mail.gmail.com>
Date: Thu, 26 Feb 2026 17:21:13 +0800
Cc: pgsql-hackers@lists.postgresql.org
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Message-Id: <08805314-299A-4941-B63E-4CC3E144E0E7@gmail.com>
References: <CAB5m2QssN6UO+ckr6ZCcV0A71mKUB6WdiTw1nHo43v4DTW1Dfg@mail.gmail.com>
To: zhanghu <kongbaik228@gmail.com>
Archived-At: <https://www.postgresql.org/message-id/08805314-299A-4941-B63E-4CC3E144E0E7%40gmail.com>
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> On Feb 26, 2026, at 15:03, zhanghu <kongbaik228@gmail.com> wrote:
>=20
> Hi,
>=20
> In check_backtrace_functions(), most accesses to the input string =
follow the pattern (*newval)[i]. However, the empty-string check is =
currently written as:
>=20
> if (*newval[0] =3D=3D '\0')
>=20
> 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.
>=20
> The attached patch rewrites it as:
>=20
> if ((*newval)[0] =3D=3D '\0')
>=20
> This change ensures semantic clarity and maintains a consistent =
dereferencing style throughout the function. No functional changes are =
introduced.
>=20
> 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 =
position 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.

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