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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: Fri, 27 Feb 2026 16:46:12 +0800
Message-ID: <CAB5m2QvGC7g03Z-ceobf+D2Q4jCZ5YKfsNOyU05peTywTzw4iA@mail.gmail.com> (raw)
In-Reply-To: <[email protected]>
References: <[email protected]>
<[email protected]>
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
>
>
>
Attachments:
[application/octet-stream] v2-0001-guc-Clarify-dereference-order-in-newval-string-ch.patch (2.1K, 3-v2-0001-guc-Clarify-dereference-order-in-newval-string-ch.patch)
download | inline diff:
From e35f0e4baa0cbcca9a969fc371ec5601152050bc Mon Sep 17 00:00:00 2001
From: zhanghu <[email protected]>
Date: Fri, 27 Feb 2026 14:39:37 +0800
Subject: [PATCH v2 1/2] guc: Clarify dereference order in newval string checks
In check_backtrace_functions(), most accesses to the input string use
the form:
(*newval)[i]
However, the empty-string check was written as:
*newval[0] == '\0'
Since [] has higher precedence than *, this is parsed as
*(newval[0]). Although it produces the same result when the index
is zero, it implies array-style access on newval and is inconsistent
with the surrounding style.
Similarly, in check_archive_directory(), the empty-string check
was written as:
*newval[0] == '\0'
In both cases, newval is a pointer-to-pointer used as an output
parameter in the GUC framework rather than a two-dimensional
character array. Rewriting these checks as:
(*newval)[0] == '\0'
makes the intended dereference order explicit.
No functional change.
Author: zhanghu <[email protected]>
---
contrib/basic_archive/basic_archive.c | 2 +-
src/backend/utils/error/elog.c | 2 +-
2 files changed, 2 insertions(+), 2 deletions(-)
diff --git a/contrib/basic_archive/basic_archive.c b/contrib/basic_archive/basic_archive.c
index 6c7f985d48b..6860e4642ee 100644
--- a/contrib/basic_archive/basic_archive.c
+++ b/contrib/basic_archive/basic_archive.c
@@ -102,7 +102,7 @@ check_archive_directory(char **newval, void **extra, GucSource source)
* Our check_configured callback also checks for this and prevents
* archiving from proceeding if it is still empty.
*/
- if (*newval == NULL || *newval[0] == '\0')
+ if (*newval == NULL || (*newval)[0] == '\0')
return true;
/*
diff --git a/src/backend/utils/error/elog.c b/src/backend/utils/error/elog.c
index 0d0bf0f6aa5..650a79b7e12 100644
--- a/src/backend/utils/error/elog.c
+++ b/src/backend/utils/error/elog.c
@@ -2627,7 +2627,7 @@ check_backtrace_functions(char **newval, void **extra, GucSource source)
return false;
}
- if (*newval[0] == '\0')
+ if ((*newval)[0] == '\0')
{
*extra = NULL;
return true;
--
2.33.0
[application/octet-stream] v2-0002-datetime-Clarify-DecodeInterval-field-parameter-t.patch (7.2K, 4-v2-0002-datetime-Clarify-DecodeInterval-field-parameter-t.patch)
download | inline diff:
From ff48c8ef74e5373a466a9866c57fd0029a123cb1 Mon Sep 17 00:00:00 2001
From: zhanghu <[email protected]>
Date: Fri, 27 Feb 2026 14:51:57 +0800
Subject: [PATCH v2 2/2] datetime: Clarify DecodeInterval field parameter type
and dereference
DecodeInterval() operates on an array of string pointers, as callers
define field as:
char *field[MAXDATEFIELDS];
The existing signature used "char **field", which could suggest a
generic pointer-to-pointer and allow callers to pass a true char **,
which would not match the function’s assumptions.
Change the parameter type to "char *field[]" to reflect the expected
array-of-pointers usage. Also add parentheses to expressions such as
*field[i], rewriting them as *(field[i]) to make the intended
dereference order explicit.
No functional change.
Author: Chao Li <[email protected]>
---
src/backend/utils/adt/datetime.c | 14 +++++++-------
src/include/utils/datetime.h | 2 +-
src/interfaces/ecpg/pgtypeslib/dt.h | 2 +-
src/interfaces/ecpg/pgtypeslib/interval.c | 14 +++++++-------
4 files changed, 16 insertions(+), 16 deletions(-)
diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index 90946db72ff..7d845700163 100644
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -3483,7 +3483,7 @@ ClearPgItmIn(struct pg_itm_in *itm_in)
* suffices.
*/
int
-DecodeInterval(char **field, int *ftype, int nf, int range,
+DecodeInterval(char *field[], int *ftype, int nf, int range,
int *dtype, struct pg_itm_in *itm_in)
{
bool force_negative = false;
@@ -3519,13 +3519,13 @@ DecodeInterval(char **field, int *ftype, int nf, int range,
* to dump in postgres style, not SQL style.)
*----------
*/
- if (IntervalStyle == INTSTYLE_SQL_STANDARD && nf > 0 && *field[0] == '-')
+ 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] == '+')
+ if (*(field[i]) == '-' || *(field[i]) == '+')
{
force_negative = false;
break;
@@ -3557,7 +3557,7 @@ DecodeInterval(char **field, int *ftype, int nf, int range,
* least one digit; there could be ':', '.', '-' embedded in
* it as well.
*/
- Assert(*field[i] == '-' || *field[i] == '+');
+ Assert(*(field[i]) == '-' || *(field[i]) == '+');
/*
* Check for signed hh:mm or hh:mm:ss. If so, process exactly
@@ -3567,7 +3567,7 @@ DecodeInterval(char **field, int *ftype, int nf, int range,
DecodeTimeForInterval(field[i] + 1, fmask, range,
&tmask, itm_in) == 0)
{
- if (*field[i] == '-')
+ if (*(field[i]) == '-')
{
/* flip the sign on time field */
if (itm_in->tm_usec == PG_INT64_MIN)
@@ -3650,7 +3650,7 @@ DecodeInterval(char **field, int *ftype, int nf, int range,
if (*cp != '\0')
return DTERR_BAD_FORMAT;
type = DTK_MONTH;
- if (*field[i] == '-')
+ if (*(field[i]) == '-')
val2 = -val2;
if (pg_mul_s64_overflow(val, MONTHS_PER_YEAR, &val))
return DTERR_FIELD_OVERFLOW;
@@ -3663,7 +3663,7 @@ DecodeInterval(char **field, int *ftype, int nf, int range,
dterr = ParseFraction(cp, &fval);
if (dterr)
return dterr;
- if (*field[i] == '-')
+ if (*(field[i]) == '-')
fval = -fval;
}
else if (*cp == '\0')
diff --git a/src/include/utils/datetime.h b/src/include/utils/datetime.h
index f77c6acd8b6..66dd871fd7f 100644
--- a/src/include/utils/datetime.h
+++ b/src/include/utils/datetime.h
@@ -316,7 +316,7 @@ extern int DecodeTimezone(const char *str, int *tzp);
extern int DecodeTimeOnly(char **field, int *ftype, int nf,
int *dtype, struct pg_tm *tm, fsec_t *fsec, int *tzp,
DateTimeErrorExtra *extra);
-extern int DecodeInterval(char **field, int *ftype, int nf, int range,
+extern int DecodeInterval(char *field[], int *ftype, int nf, int range,
int *dtype, struct pg_itm_in *itm_in);
extern int DecodeISO8601Interval(char *str,
int *dtype, struct pg_itm_in *itm_in);
diff --git a/src/interfaces/ecpg/pgtypeslib/dt.h b/src/interfaces/ecpg/pgtypeslib/dt.h
index 00a45799d55..47df0df4739 100644
--- a/src/interfaces/ecpg/pgtypeslib/dt.h
+++ b/src/interfaces/ecpg/pgtypeslib/dt.h
@@ -311,7 +311,7 @@ do { \
#define TIMESTAMP_IS_NOEND(j) ((j) == DT_NOEND)
#define TIMESTAMP_NOT_FINITE(j) (TIMESTAMP_IS_NOBEGIN(j) || TIMESTAMP_IS_NOEND(j))
-int DecodeInterval(char **field, int *ftype, int nf, int *dtype, struct tm *tm, fsec_t *fsec);
+int DecodeInterval(char *field[], int *ftype, int nf, int *dtype, struct tm *tm, fsec_t *fsec);
int DecodeTime(char *str, int *tmask, struct tm *tm, fsec_t *fsec);
void EncodeDateTime(struct tm *tm, fsec_t fsec, bool print_tz, int tz, const char *tzn, int style, char *str, bool EuroDates);
void EncodeInterval(struct tm *tm, fsec_t fsec, int style, char *str);
diff --git a/src/interfaces/ecpg/pgtypeslib/interval.c b/src/interfaces/ecpg/pgtypeslib/interval.c
index e452a088f9e..4d0e75d4dd4 100644
--- a/src/interfaces/ecpg/pgtypeslib/interval.c
+++ b/src/interfaces/ecpg/pgtypeslib/interval.c
@@ -323,7 +323,7 @@ DecodeISO8601Interval(char *str,
* int IntervalStyle = INTSTYLE_POSTGRES;
*/
int
-DecodeInterval(char **field, int *ftype, int nf, /* int range, */
+DecodeInterval(char *field[], int *ftype, int nf, /* int range, */
int *dtype, struct /* pg_ */ tm *tm, fsec_t *fsec)
{
int IntervalStyle = INTSTYLE_POSTGRES_VERBOSE;
@@ -362,7 +362,7 @@ DecodeInterval(char **field, int *ftype, int nf, /* int range, */
* least one digit; there could be ':', '.', '-' embedded in
* it as well.
*/
- Assert(*field[i] == '-' || *field[i] == '+');
+ Assert(*(field[i]) == '-' || *(field[i]) == '+');
/*
* Try for hh:mm or hh:mm:ss. If not, fall through to
@@ -373,7 +373,7 @@ DecodeInterval(char **field, int *ftype, int nf, /* int range, */
DecodeTime(field[i] + 1, /* INTERVAL_FULL_RANGE, */
&tmask, tm, fsec) == 0)
{
- if (*field[i] == '-')
+ if (*(field[i]) == '-')
{
/* flip the sign on all fields */
tm->tm_hour = -tm->tm_hour;
@@ -447,7 +447,7 @@ DecodeInterval(char **field, int *ftype, int nf, /* int range, */
if (*cp != '\0')
return DTERR_BAD_FORMAT;
type = DTK_MONTH;
- if (*field[i] == '-')
+ if (*(field[i]) == '-')
val2 = -val2;
val = val * MONTHS_PER_YEAR + val2;
fval = 0;
@@ -459,7 +459,7 @@ DecodeInterval(char **field, int *ftype, int nf, /* int range, */
if (*cp != '\0' || errno != 0)
return DTERR_BAD_FORMAT;
- if (*field[i] == '-')
+ if (*(field[i]) == '-')
fval = -fval;
}
else if (*cp == '\0')
@@ -622,14 +622,14 @@ DecodeInterval(char **field, int *ftype, int nf, /* int range, */
* to dump in postgres style, not SQL style.)
*----------
*/
- if (IntervalStyle == INTSTYLE_SQL_STANDARD && *field[0] == '-')
+ 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] == '+')
+ if (*(field[i]) == '-' || *(field[i]) == '+')
{
more_signs = true;
break;
--
2.33.0
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To: [email protected]
Cc: [email protected], [email protected], [email protected], [email protected], [email protected]
Subject: Re: guc: make dereference style consistent in check_backtrace_functions
In-Reply-To: <CAB5m2QvGC7g03Z-ceobf+D2Q4jCZ5YKfsNOyU05peTywTzw4iA@mail.gmail.com>
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