Fix behavior when converting a float infinity to numeric.

tglsfdc · tglsfdc · commit c38575edce0d · 2017-09-27T17:05:53.000-04:00
float8_numeric() and float4_numeric() failed to consider the possibility that the input is an IEEE infinity. The results depended on the platform-specific behavior of sprintf(): on most platforms you'd get something like ERROR: invalid input syntax for type numeric: "inf" but at least on Windows it's possible for the conversion to succeed and deliver a finite value (typically 1), due to a nonstandard output format from sprintf and lack of syntax error checking in these functions. Since our numeric type lacks the concept of infinity, a suitable conversion is impossible; the best thing to do is throw an explicit error before letting sprintf do its thing. While at it, let's use snprintf not sprintf. Overrunning the buffer should be impossible if sprintf does what it's supposed to, but this is cheap insurance against a stack smash if it doesn't. Problem reported by Taiki Kondo. Patch by me based on fix suggestion from KaiGai Kohei. Back-patch to all supported branches. Discussion: https://postgr.es/m/12A9442FBAE80D4E8953883E0B84E088C8C7A2@BPXM01GP.gisp.nec.co.jp
diff --git a/src/backend/utils/adt/numeric.c b/src/backend/utils/adt/numeric.c
@@ -2421,7 +2421,12 @@ float8_numeric(PG_FUNCTION_ARGS)
 	if (isnan(val))
 		PG_RETURN_NUMERIC(make_result(&const_nan));
 
-	sprintf(buf, "%.*g", DBL_DIG, val);
+	if (isinf(val))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot convert infinity to numeric")));
+
+	snprintf(buf, sizeof(buf), "%.*g", DBL_DIG, val);
 
 	init_var(&result);
 
@@ -2483,7 +2488,12 @@ float4_numeric(PG_FUNCTION_ARGS)
 	if (isnan(val))
 		PG_RETURN_NUMERIC(make_result(&const_nan));
 
-	sprintf(buf, "%.*g", FLT_DIG, val);
+	if (isinf(val))
+		ereport(ERROR,
+				(errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
+				 errmsg("cannot convert infinity to numeric")));
+
+	snprintf(buf, sizeof(buf), "%.*g", FLT_DIG, val);
 
 	init_var(&result);
 
diff --git a/src/test/regress/expected/numeric.out b/src/test/regress/expected/numeric.out
@@ -708,6 +708,27 @@ SELECT * FROM fract_only;
 (6 rows)
 
 DROP TABLE fract_only;
+-- Check inf/nan conversion behavior
+SELECT 'NaN'::float8::numeric;
+ numeric 
+---------
+     NaN
+(1 row)
+
+SELECT 'Infinity'::float8::numeric;
+ERROR:  cannot convert infinity to numeric
+SELECT '-Infinity'::float8::numeric;
+ERROR:  cannot convert infinity to numeric
+SELECT 'NaN'::float4::numeric;
+ numeric 
+---------
+     NaN
+(1 row)
+
+SELECT 'Infinity'::float4::numeric;
+ERROR:  cannot convert infinity to numeric
+SELECT '-Infinity'::float4::numeric;
+ERROR:  cannot convert infinity to numeric
 -- Simple check that ceil(), floor(), and round() work correctly
 CREATE TABLE ceil_floor_round (a numeric);
 INSERT INTO ceil_floor_round VALUES ('-5.5');
diff --git a/src/test/regress/sql/numeric.sql b/src/test/regress/sql/numeric.sql
@@ -655,6 +655,14 @@ INSERT INTO fract_only VALUES (8, '0.00017');
 SELECT * FROM fract_only;
 DROP TABLE fract_only;
 
+-- Check inf/nan conversion behavior
+SELECT 'NaN'::float8::numeric;
+SELECT 'Infinity'::float8::numeric;
+SELECT '-Infinity'::float8::numeric;
+SELECT 'NaN'::float4::numeric;
+SELECT 'Infinity'::float4::numeric;
+SELECT '-Infinity'::float4::numeric;
+
 -- Simple check that ceil(), floor(), and round() work correctly
 CREATE TABLE ceil_floor_round (a numeric);
 INSERT INTO ceil_floor_round VALUES ('-5.5');
