From b9c4820bdd5f0152a9ba077308d521edb782eff9 Mon Sep 17 00:00:00 2001
From: Alexey Milovidov <milovidov@yandex-team.ru>
Date: Sun, 2 Sep 2018 06:52:04 +0300
Subject: [PATCH] Addition to prev. revision [#CLICKHOUSE-2]

---
 dbms/src/Functions/FunctionsStringSearch.cpp | 12 ++++++++----
 dbms/src/Functions/FunctionsVisitParam.h     |  3 ++-
 dbms/src/Functions/GatherUtils/Algorithms.h  |  2 +-
 3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/dbms/src/Functions/FunctionsStringSearch.cpp b/dbms/src/Functions/FunctionsStringSearch.cpp
index 4545aa25784..2c8b575b6b8 100644
--- a/dbms/src/Functions/FunctionsStringSearch.cpp
+++ b/dbms/src/Functions/FunctionsStringSearch.cpp
@@ -191,7 +191,8 @@ struct PositionImpl
             ++i;
         }
 
-        memset(&res[i], 0, (res.size() - i) * sizeof(res[0]));
+        if (i < res.size())
+            memset(&res[i], 0, (res.size() - i) * sizeof(res[0]));
     }
 
     /// Search for substring in string.
@@ -389,7 +390,8 @@ struct MatchImpl
             }
 
             /// Tail, in which there can be no substring.
-            memset(&res[i], revert, (res.size() - i) * sizeof(res[0]));
+            if (i < res.size())
+                memset(&res[i], revert, (res.size() - i) * sizeof(res[0]));
         }
         else
         {
@@ -407,7 +409,8 @@ struct MatchImpl
             {
                 if (!regexp->getRE2()) /// An empty regexp. Always matches.
                 {
-                    memset(res.data(), 1, size * sizeof(res[0]));
+                    if (size)
+                        memset(res.data(), 1, size * sizeof(res[0]));
                 }
                 else
                 {
@@ -488,7 +491,8 @@ struct MatchImpl
                     ++i;
                 }
 
-                memset(&res[i], revert, (res.size() - i) * sizeof(res[0]));
+                if (i < res.size())
+                    memset(&res[i], revert, (res.size() - i) * sizeof(res[0]));
             }
         }
     }
diff --git a/dbms/src/Functions/FunctionsVisitParam.h b/dbms/src/Functions/FunctionsVisitParam.h
index 897414e6498..82bf8946e7c 100644
--- a/dbms/src/Functions/FunctionsVisitParam.h
+++ b/dbms/src/Functions/FunctionsVisitParam.h
@@ -194,7 +194,8 @@ struct ExtractParamImpl
             ++i;
         }
 
-        memset(&res[i], 0, (res.size() - i) * sizeof(res[0]));
+        if (res.size() > i)
+            memset(&res[i], 0, (res.size() - i) * sizeof(res[0]));
     }
 
     static void constant_constant(const std::string & data, std::string needle, ResultType & res)
diff --git a/dbms/src/Functions/GatherUtils/Algorithms.h b/dbms/src/Functions/GatherUtils/Algorithms.h
index fee172ce394..e4027d54cdf 100644
--- a/dbms/src/Functions/GatherUtils/Algorithms.h
+++ b/dbms/src/Functions/GatherUtils/Algorithms.h
@@ -105,7 +105,7 @@ inline ALWAYS_INLINE void writeSlice(const Slice & slice, NullableArraySink<Arra
 
     if (slice.size == 1) /// Always true for ValueSlice.
         sink.null_map[sink.current_offset] = 0;
-    else
+    else if (slice.size)
         memset(&sink.null_map[sink.current_offset], 0, slice.size * sizeof(UInt8));
 
     writeSlice(slice, static_cast<ArraySink &>(sink));