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help / color / mirror / Atom feedFrom: zhanghu <[email protected]>
To: Chao Li <[email protected]>
Cc: Álvaro Herrera <[email protected]>
Cc: Junwang Zhao <[email protected]>
Cc: [email protected]
Subject: Re: guc: make dereference style consistent in check_backtrace_functions
Date: Mon, 2 Mar 2026 11:17:56 +0800
Message-ID: <CAB5m2QurkJENd-fd2gKKEHAjwmTxYCqm4uuSnpwXZroE6xp3MQ@mail.gmail.com> (raw)
In-Reply-To: <CAB5m2QvGC7g03Z-ceobf+D2Q4jCZ5YKfsNOyU05peTywTzw4iA@mail.gmail.com>
References: <[email protected]>
<[email protected]>
<CAB5m2QvGC7g03Z-ceobf+D2Q4jCZ5YKfsNOyU05peTywTzw4iA@mail.gmail.com>
zhanghu <[email protected]> 于2026年2月27日周五 16:46写道：
>
>
>
> Chao Li <[email protected]> 于2026年2月27日周五 09:34写道：
>>
>>
>>
>> > On Feb 26, 2026, at 20:37, Álvaro Herrera <[email protected]> wrote:
>> >
>> > There is at least one more place in the code where this is done.
>> >
>>
>> I did a search with the command: grep -RInE '\*[[:space:]]*[A-Za-z_][A-Za-z0-9_]*\[0\]' src contrib --include='*.c'
>>
>> Excluding irrelevant results, there are 3 more occurrences:
>>
>> 1 - contrib/basic_archive/basic_archive.c line 105
>> ```
>> if (*newval == NULL || *newval[0] == '\0')
>> return true;
>> ```
>>
>> Here, the code checks *newval first, which implies that the subsequent *newval[0] is unintentional syntax.
>>
>> 2 - src/interfaces/ecpg/pgtypeslib/interval.c line 62
>> ```
>> int
>> DecodeInterval(char **field, int *ftype, int nf, /* int range, */
>> int *dtype, struct /* pg_ */ tm *tm, fsec_t *fsec)
>> {
>> ...
>> if (IntervalStyle == INTSTYLE_SQL_STANDARD && *field[0] == '-')
>> {
>> /* Check for additional explicit signs */
>> bool more_signs = false;
>>
>> for (i = 1; i < nf; i++)
>> {
>> if (*field[i] == '-' || *field[i] == '+')
>> {
>> more_signs = true;
>> break;
>> }
>> }
>> ```
>>
>> 3 - src/backend/utils/adt/datatime.c line 3522
>> ```
>> int
>> DecodeInterval(char **field, int *ftype, int nf, int range,
>> int *dtype, struct pg_itm_in *itm_in)
>> {
>> ...
>> if (IntervalStyle == INTSTYLE_SQL_STANDARD && nf > 0 && *field[0] == '-')
>> {
>> force_negative = true;
>> /* Check for additional explicit signs */
>> for (i = 1; i < nf; i++)
>> {
>> if (*field[i] == '-' || *field[i] == '+')
>> {
>> force_negative = false;
>> break;
>> }
>> }
>> }
>> ```
>>
>> Where 2&3 makes this patch more interesting.
>>
>> Both occurrences are inside functions named DecodeInterval. For non-zero i, the code also performs *field[i]:
>>
>> Given this code has been there for years, I don’t believe it is a bug. I checked the callers of DecodeInterval in both files and found that field is defined as:
>> ```
>> char *field[MAXDATEFIELDS];
>> ```
>>
>> This explains why *field[i] works; it is doing the intended thing by getting the first character of the string at array position i.
>>
>> However, since the precedence between the [] and * operators frequently confuses people, I suggest adding parentheses to make the intention explicit as *(field[i]). Furthermore, I think we should change the function signatures to use the type char *field[] to reflect the actual type the functions expect. If a caller were to pass a true char ** typed field to DecodeInterval, the current logic would result in a bug.
>>
>> See the attached diff for my suggested changes.
>>
>> Best regards,
>> --
>> Chao Li (Evan)
>> HighGo Software Co., Ltd.
>> https://www.highgo.com/
>>
>> Hi,
>>
>> Thank you all for the reviews and detailed feedback.
>>
>> Álvaro, thanks for pointing out that there were additional
>> occurrences elsewhere in the tree. I have updated the original
>> patch to address those cases; the revised version is attached
>> as v2-0001.
>>
>> I also appreciate the review and suggestions from
>> Chao and Junwang.
>>
>> Regarding the additional changes suggested by Chao: they go
>> somewhat beyond the original scope of my original patch.
>> To keep the discussion concrete, I have included Chao’s proposed
>> diff as a separate patch (v2-0002) so it can be reviewed independently.
>>
>> I have reviewed v2-0002 locally, and it looks good to me.
>>
>> Thanks again for the guidance.
>>
>> Regards,
>> Zhang Hu
>>
>>
Hi,
I am planning to add this patch to the current CommitFest, but when
logging in to commitfest.postgresql.org I get the message:
“You have not passed the cool off period yet.”
It seems my account is still within the cool-off period after registration.
Could someone please add this patch to the CommitFest on my behalf?
Thanks.
Best regards,
Zhang Hu
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Subject: Re: guc: make dereference style consistent in check_backtrace_functions
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