MDEV-5173 Cppcheck report

fixed bugs, found by cppcheck

mysys/ma_dyncol.c

@@ -1616,7 +1616,7 @@ dynamic_new_column_store(DYNAMIC_COLUMN *str,
   enum enum_dyncol_func_result rc= ER_DYNCOL_RESOURCE;
   size_t all_headers_size;
 
-  if (!(columns_order= malloc(sizeof(void*)*column_count)))
+  if (column_count && !(columns_order= malloc(sizeof(void*)*column_count)))
     return ER_DYNCOL_RESOURCE;
   if (new_str || str->str == 0)
   {
@@ -3959,7 +3959,7 @@ mariadb_dyncol_val_long(longlong *ll, DYNAMIC_COLUMN_VALUE *val)
           {
             sign= -1;
             src++;
-          } else if (*src == '-')
+          } else if (*src == '+')
             src++;
           while(len && my_isdigit(&my_charset_latin1, *src))
           {
@@ -4032,7 +4032,7 @@ mariadb_dyncol_val_double(double *dbl, DYNAMIC_COLUMN_VALUE *val)
     case DYN_COL_STRING:
       {
         char *str, *end;
-        if ((str= malloc(val->x.string.value.length + 1)))
+        if (!(str= malloc(val->x.string.value.length + 1)))
           return ER_DYNCOL_RESOURCE;
         memcpy(str, val->x.string.value.str, val->x.string.value.length);
         str[val->x.string.value.length]= '\0';

sql/filesort_utils.h

@@ -95,7 +95,7 @@ class Filesort_buffer
   bool check_sort_buffer_properties(uint num_records,  uint record_length)
   {
     return (static_cast<uint>(m_idx_array.size()) == num_records &&
-            m_record_length == m_record_length);
+            m_record_length == record_length);
   }
 
   /// Frees the buffer.