r17038 - Avoid undefined behaviour in next_float functions (Raúl Marín)

[Raul]

Author: algunenano
Date: 2018-11-21 03:46:43 -0800 (Wed, 21 Nov 2018)
New Revision: 17038

Modified:
   trunk/NEWS
   trunk/liblwgeom/cunit/cu_libgeom.c
   trunk/liblwgeom/lwgeom_api.c
Log:
Avoid undefined behaviour in next_float functions (Raúl Marín)

Closes #4247
Closes https://github.com/postgis/postgis/pull/339



Modified: trunk/NEWS
===================================================================
--- trunk/NEWS	2018-11-21 11:45:43 UTC (rev 17037)
+++ trunk/NEWS	2018-11-21 11:46:43 UTC (rev 17038)
@@ -39,6 +39,7 @@
   - #4326, Allocate enough memory in gidx_to_string (Raúl Marín)
   - #4190, Avoid undefined behaviour in gserialized_estimate (Raúl Marín)
   - #4233, Fix undefined behaviour in gserialized_spgist_picksplit_nd (Raúl Marín)
+  - #4247, Avoid undefined behaviour in next_float functions (Raúl Marín)
 
 PostGIS 2.5.0
 2018/09/23

Modified: trunk/liblwgeom/cunit/cu_libgeom.c
===================================================================
--- trunk/liblwgeom/cunit/cu_libgeom.c	2018-11-21 11:45:43 UTC (rev 17037)
+++ trunk/liblwgeom/cunit/cu_libgeom.c	2018-11-21 11:46:43 UTC (rev 17038)
@@ -688,6 +688,26 @@
 	f = next_float_up(d);
 	d = next_float_up(f);
 	CU_ASSERT_DOUBLE_EQUAL(f,d, 0.0000001);
+
+	d = DBL_MAX;
+	f = next_float_up(d);
+	d = next_float_up(f);
+	CU_ASSERT_DOUBLE_EQUAL(f, d, 0.0000001);
+
+	d = DBL_MAX;
+	f = next_float_down(d);
+	d = next_float_down(f);
+	CU_ASSERT_DOUBLE_EQUAL(f, d, 0.0000001);
+
+	d = -DBL_MAX;
+	f = next_float_up(d);
+	d = next_float_up(f);
+	CU_ASSERT_DOUBLE_EQUAL(f, d, 0.0000001);
+
+	d = -DBL_MAX;
+	f = next_float_down(d);
+	d = next_float_down(f);
+	CU_ASSERT_DOUBLE_EQUAL(f, d, 0.0000001);
 }
 
 /*

Modified: trunk/liblwgeom/lwgeom_api.c
===================================================================
--- trunk/liblwgeom/lwgeom_api.c	2018-11-21 11:45:43 UTC (rev 17037)
+++ trunk/liblwgeom/lwgeom_api.c	2018-11-21 11:46:43 UTC (rev 17038)
@@ -50,7 +50,12 @@
 inline float
 next_float_down(double d)
 {
-	float result  = d;
+	float result;
+	if (d > (double)FLT_MAX)
+		return FLT_MAX;
+	if (d <= (double)-FLT_MAX)
+		return -FLT_MAX;
+	result = d;
 
 	if ( ((double)result) <=d )
 		return result;
@@ -66,7 +71,12 @@
 inline float
 next_float_up(double d)
 {
-	float result  = d;
+	float result;
+	if (d >= (double)FLT_MAX)
+		return FLT_MAX;
+	if (d < (double)-FLT_MAX)
+		return -FLT_MAX;
+	result = d;
 
 	if ( ((double)result) >=d )
 		return result;