Date: Thu, 15 Aug 2024 16:34:30 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: jian he <jian.universality@gmail.com>
Cc: Joseph Koshakow <koshy44@gmail.com>,
	Heikki Linnakangas <hlinnaka@iki.fi>,
	Matthew Kim <matthewkmkim@gmail.com>,
	Alexander Lakhin <exclusion@gmail.com>,
	Tom Lane <tgl@sss.pgh.pa.us>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	Andres Freund <andres@anarazel.de>
Subject: Re: Remove dependence on integer wrapping
Message-ID: <Zr50ZpSyrBx0EHfR@nathan>
References: <CAAvxfHfuxiMG4_YB5oBmJtK7mQx6FRKcUhNueXGwKT6_r=4W_Q@mail.gmail.com>
 <CACJufxFUKTQx8wUpxtRPT31D+a7fNxAL_A_-S4XaR-oZkKEgxA@mail.gmail.com>
 <ZrvUOkL19KHEH2sb@nathan>
 <ZrwfgNyDXy99NUOS@nathan>
 <875ad3ec-f216-487e-baad-cdbaf32c1fcf@iki.fi>
 <ZrznaJTIOPgSjEJ7@nathan>
 <CAAvxfHc2Smk92cJX4aUju1AdW_RpNN8csEj5rvf29b-YFHRmfQ@mail.gmail.com>
 <Zrz0Zv4PVFxieEii@nathan>
 <CACJufxH-uLR5SnnmVbGYj7Oy90zF_pYV3G_HxfbJ6Lu3XKGXxQ@mail.gmail.com>
 <Zr5M3KxOZlEZRZIN@nathan>
MIME-Version: 1.0
Content-Type: multipart/mixed; boundary="XFoT1JusIWT5wkIc"
Content-Disposition: inline
In-Reply-To: <Zr5M3KxOZlEZRZIN@nathan>
Archived-At: <https://www.postgresql.org/message-id/Zr50ZpSyrBx0EHfR%40nathan>
Precedence: bulk


--XFoT1JusIWT5wkIc
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline

I've committed 0001.  Now to 0002...

-		if (-element > nelements)
+		if (element == PG_INT32_MIN || -element > nelements)

This seems like a good opportunity to use our new pg_abs_s32() function,
and godbolt.org [0] seems to indicate that it might produce better code,
too (at least to my eye).  I've attached an updated version of the patch
with this change.  Barring additional feedback, I plan to commit this one
shortly.

[0] https://godbolt.org/z/57P4vvGYf

-- 
nathan

--XFoT1JusIWT5wkIc
Content-Type: text/plain; charset=us-ascii
Content-Disposition: attachment;
	filename="v23-0001-Remove-dependence-on-integer-wrapping-for-jsonb.patch"

From 62677b351cf18dee37dc0d9253bd694fe6fbf26a Mon Sep 17 00:00:00 2001
From: Joseph Koshakow <koshy44@gmail.com>
Date: Sat, 6 Jul 2024 15:41:09 -0400
Subject: [PATCH v23 1/1] Remove dependence on integer wrapping for jsonb

This commit updates various jsonb operators and functions to no longer
rely on integer wrapping for correctness. Not all compilers support
-fwrapv, so it's best not to rely on it.
---
 src/backend/utils/adt/jsonfuncs.c   |  7 ++++---
 src/test/regress/expected/jsonb.out | 12 ++++++++++++
 src/test/regress/sql/jsonb.sql      |  2 ++
 3 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/backend/utils/adt/jsonfuncs.c b/src/backend/utils/adt/jsonfuncs.c
index 5ecb9fffae..1f8ea51e6a 100644
--- a/src/backend/utils/adt/jsonfuncs.c
+++ b/src/backend/utils/adt/jsonfuncs.c
@@ -18,6 +18,7 @@
 
 #include "access/htup_details.h"
 #include "catalog/pg_type.h"
+#include "common/int.h"
 #include "common/jsonapi.h"
 #include "common/string.h"
 #include "fmgr.h"
@@ -946,7 +947,7 @@ jsonb_array_element(PG_FUNCTION_ARGS)
 	{
 		uint32		nelements = JB_ROOT_COUNT(jb);
 
-		if (-element > nelements)
+		if (pg_abs_s32(element) > nelements)
 			PG_RETURN_NULL();
 		else
 			element += nelements;
@@ -5426,7 +5427,7 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 
 	if (idx < 0)
 	{
-		if (-idx > nelems)
+		if (pg_abs_s32(idx) > nelems)
 		{
 			/*
 			 * If asked to keep elements position consistent, it's not allowed
@@ -5438,7 +5439,7 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 						 errmsg("path element at position %d is out of range: %d",
 								level + 1, idx)));
 			else
-				idx = INT_MIN;
+				idx = PG_INT32_MIN;
 		}
 		else
 			idx = nelems + idx;
diff --git a/src/test/regress/expected/jsonb.out b/src/test/regress/expected/jsonb.out
index e66d760189..a9d93052fc 100644
--- a/src/test/regress/expected/jsonb.out
+++ b/src/test/regress/expected/jsonb.out
@@ -680,6 +680,18 @@ select '"foo"'::jsonb -> 'z';
  
 (1 row)
 
+select '[]'::jsonb -> -2147483648;
+ ?column? 
+----------
+ 
+(1 row)
+
+select jsonb_delete_path('{"a":[]}', '{"a",-2147483648}');
+ jsonb_delete_path 
+-------------------
+ {"a": []}
+(1 row)
+
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> null::text;
  ?column? 
 ----------
diff --git a/src/test/regress/sql/jsonb.sql b/src/test/regress/sql/jsonb.sql
index 97bc2242a1..6a18577ead 100644
--- a/src/test/regress/sql/jsonb.sql
+++ b/src/test/regress/sql/jsonb.sql
@@ -204,6 +204,8 @@ select '[{"b": "c"}, {"b": "cc"}]'::jsonb -> 'z';
 select '{"a": "c", "b": null}'::jsonb -> 'b';
 select '"foo"'::jsonb -> 1;
 select '"foo"'::jsonb -> 'z';
+select '[]'::jsonb -> -2147483648;
+select jsonb_delete_path('{"a":[]}', '{"a",-2147483648}');
 
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> null::text;
 select '{"a": [{"b": "c"}, {"b": "cc"}]}'::jsonb ->> null::int;
-- 
2.39.3 (Apple Git-146)


--XFoT1JusIWT5wkIc--