Fix integer to_char() overflow with V format

When to_char() formatted an integer value with a V pattern, it could
return an incorrect result instead of reporting an overflow. V shifts
the decimal point by multiplying the input value by a power of ten before
formatting it, so, for example,

    to_char(3, '9V999999999')

requires computing 3 * 10^9. This result does not fit in int4, but
the integer variant of to_char() performed the multiplication using a
plain int32 expression. The intermediate result could therefore
overflow, causing the function to output incorrect digits instead of
raising "integer out of range".

Use dtoi4() and int4mul() for this calculation so that both an
out-of-range multiplier and an out-of-range product are detected, as
with ordinary integer arithmetic. This also matches the existing int8
implementation, which uses dtoi8() and int8mul() for the same
operation.

After this change, to_char() with V format either returns the
correctly formatted result when the scaled value fits in int4, or
raises "integer out of range" when it does not.

Backpatch to all supported versions.

Reported-by: Andrey Rachitskiy <pl0h0yp1@gmail.com>
Author: Andrey Rachitskiy <pl0h0yp1@gmail.com>
Reviewed-by: Miłosz Bieniek <bieniek.milosz@proton.me>
Reviewed-by: Fujii Masao <masao.fujii@gmail.com>
Discussion: https://postgr.es/m/CAB8bMivEfqZxOVdzc3kZDN++XshmkEz2t7dfGBU8+oUm864EZg@mail.gmail.com
Backpatch-through: 14

3 files changed, 45 insertions, 7 deletions

diff --git a/src/backend/utils/adt/formatting.c b/src/backend/utils/adt/formatting.c
index 9460ee1b7c6..9bd5725e841 100644
--- a/src/backend/utils/adt/formatting.c
+++ b/src/backend/utils/adt/formatting.c
@@ -6688,15 +6688,17 @@ int4_to_char(PG_FUNCTION_ARGS)
 
 		if (IS_MULTI(&Num))
 		{
-			orgnum = DatumGetCString(DirectFunctionCall1(int4out,
-														 Int32GetDatum(value * ((int32) pow((double) 10, (double) Num.multi)))));
+			double		multi = pow((double) 10, (double) Num.multi);
+
+			value = DatumGetInt32(DirectFunctionCall2(int4mul,
+													  Int32GetDatum(value),
+													  DirectFunctionCall1(dtoi4,
+																		  Float8GetDatum(multi))));
 			Num.pre += Num.multi;
 		}
-		else
-		{
-			orgnum = DatumGetCString(DirectFunctionCall1(int4out,
-														 Int32GetDatum(value)));
-		}
+
+		orgnum = DatumGetCString(DirectFunctionCall1(int4out,
+													 Int32GetDatum(value)));
 
 		if (*orgnum == '-')
 		{
diff --git a/src/test/regress/expected/int4.out b/src/test/regress/expected/int4.out
index b1a15888ef8..fca591fad84 100644
--- a/src/test/regress/expected/int4.out
+++ b/src/test/regress/expected/int4.out
@@ -370,6 +370,33 @@ SELECT (-2147483648)::int4 % (-1)::int2;
         0
 (1 row)
 
+-- check overflow of to_char() with V format
+SELECT to_char(2, '9V999999999'); -- 10^9
+   to_char   
+-------------
+  2000000000
+(1 row)
+
+SELECT to_char(3, '9V999999999'); -- 10^9
+ERROR:  integer out of range
+SELECT to_char(214748364, '999999999V9');
+   to_char   
+-------------
+  2147483640
+(1 row)
+
+SELECT to_char(2147483647, '9V9');
+ERROR:  integer out of range
+SELECT to_char(-2, '9V999999999'); -- 10^9
+   to_char   
+-------------
+ -2000000000
+(1 row)
+
+SELECT to_char((-2147483648)::int4, '9V9');
+ERROR:  integer out of range
+SELECT to_char(1, '9V9999999999'); -- 10^10
+ERROR:  integer out of range
 -- check rounding when casting from float
 SELECT x, x::int4 AS int4_value
 FROM (VALUES (-2.5::float8),
diff --git a/src/test/regress/sql/int4.sql b/src/test/regress/sql/int4.sql
index e9d89e8111f..d27f5500e01 100644
--- a/src/test/regress/sql/int4.sql
+++ b/src/test/regress/sql/int4.sql
@@ -126,6 +126,15 @@ SELECT (-2147483648)::int4 * (-1)::int2;
 SELECT (-2147483648)::int4 / (-1)::int2;
 SELECT (-2147483648)::int4 % (-1)::int2;
 
+-- check overflow of to_char() with V format
+SELECT to_char(2, '9V999999999'); -- 10^9
+SELECT to_char(3, '9V999999999'); -- 10^9
+SELECT to_char(214748364, '999999999V9');
+SELECT to_char(2147483647, '9V9');
+SELECT to_char(-2, '9V999999999'); -- 10^9
+SELECT to_char((-2147483648)::int4, '9V9');
+SELECT to_char(1, '9V9999999999'); -- 10^10
+
 -- check rounding when casting from float
 SELECT x, x::int4 AS int4_value
 FROM (VALUES (-2.5::float8),