[HACKERS] [PATCH 2/3] Fix x + 1 < x overflow checks

[Xi Wang]

icc optimizes away x + 1 < x because signed integer overflow is
undefined behavior in C.  Instead, simply check if x is INT_MAX.
---
 src/backend/utils/adt/float.c |    8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/src/backend/utils/adt/float.c b/src/backend/utils/adt/float.c
index b73e0d5..344b092 100644
--- a/src/backend/utils/adt/float.c
+++ b/src/backend/utils/adt/float.c
@@ -2764,12 +2764,12 @@ width_bucket_float8(PG_FUNCTION_ARGS)
                        result = 0;
                else if (operand >= bound2)
                {
-                       result = count + 1;
                        /* check for overflow */
-                       if (result < count)
+                       if (count == INT_MAX)
                                ereport(ERROR,
                                                
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                                                 errmsg("integer out of 
range")));
+                       result = count + 1;
                }
                else
                        result = ((float8) count * (operand - bound1) / (bound2 
- bound1)) + 1;
@@ -2780,12 +2780,12 @@ width_bucket_float8(PG_FUNCTION_ARGS)
                        result = 0;
                else if (operand <= bound2)
                {
-                       result = count + 1;
                        /* check for overflow */
-                       if (result < count)
+                       if (count == INT_MAX)
                                ereport(ERROR,
                                                
(errcode(ERRCODE_NUMERIC_VALUE_OUT_OF_RANGE),
                                                 errmsg("integer out of 
range")));
+                       result = count + 1;
                }
                else
                        result = ((float8) count * (bound1 - operand) / (bound1 
- bound2)) + 1;
-- 
1.7.10.4



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