Fix for Bug#32748: Inconsistent handling of assignments to

general_log_file/slow_query_log_file.

The problem was that log file path was rejected if directory
path was empty. The fix is to reject log file path only if it
is entirely empty.

mysql-test/r/log_state.result

@@ -249,4 +249,25 @@ set global slow_query_log_file= NULL;
 ERROR 42000: Variable 'slow_query_log_file' can't be set to the value of 'NULL'
 set global general_log_file= @old_general_log_file;
 set global slow_query_log_file= @old_slow_query_log_file;
+
+# --
+# -- Bug#32748: Inconsistent handling of assignments to
+# -- general_log_file/slow_query_log_file.
+# --
+
+SET @general_log_file_saved = @@global.general_log_file;
+SET @slow_query_log_file_saved = @@global.slow_query_log_file;
+
+SET GLOBAL general_log_file = 'bug32748.query.log';
+SET GLOBAL slow_query_log_file = 'bug32748.slow.log';
+
+SHOW VARIABLES LIKE '%log_file';
+Variable_name	Value
+general_log_file	bug32748.query.log
+slow_query_log_file	bug32748.slow.log
+
+SET GLOBAL general_log_file = @general_log_file_saved;
+SET GLOBAL slow_query_log_file = @slow_query_log_file_saved;
+
+# -- End of Bug#32748.
 End of 5.1 tests

mysql-test/t/log_state.test

@@ -231,6 +231,34 @@ set global slow_query_log_file= NULL;
 set global general_log_file= @old_general_log_file;
 set global slow_query_log_file= @old_slow_query_log_file;
 
+###########################################################################
+
+--echo
+--echo # --
+--echo # -- Bug#32748: Inconsistent handling of assignments to
+--echo # -- general_log_file/slow_query_log_file.
+--echo # --
+
+--echo
+SET @general_log_file_saved = @@global.general_log_file;
+SET @slow_query_log_file_saved = @@global.slow_query_log_file;
+
+--echo
+SET GLOBAL general_log_file = 'bug32748.query.log';
+SET GLOBAL slow_query_log_file = 'bug32748.slow.log';
+
+--echo
+SHOW VARIABLES LIKE '%log_file';
+
+--echo
+SET GLOBAL general_log_file = @general_log_file_saved;
+SET GLOBAL slow_query_log_file = @slow_query_log_file_saved;
+
+--echo
+--echo # -- End of Bug#32748.
+
+###########################################################################
+
 --echo End of 5.1 tests
 
 --enable_ps_protocol

sql/set_var.cc

@@ -2399,6 +2399,7 @@ static int  sys_check_log_path(THD *thd,  set_var *var)
   MY_STAT f_stat;
   String str(buff, sizeof(buff), system_charset_info), *res;
   const char *log_file_str;
+  size_t path_length;
 
   if (!(res= var->value->val_str(&str)))
     goto err;
@@ -2406,25 +2407,43 @@ static int  sys_check_log_path(THD *thd,  set_var *var)
   log_file_str= res->c_ptr();
   bzero(&f_stat, sizeof(MY_STAT));
 
-  (void) unpack_filename(path, log_file_str);
+  path_length= unpack_filename(path, log_file_str);
+
+  if (!path_length)
+  {
+    /* File name is empty. */
+
+    goto err;
+  }
+
   if (my_stat(path, &f_stat, MYF(0)))
   {
-    /* Check if argument is a file and we have 'write' permission */
+    /*
+      A file system object exists. Check if argument is a file and we have
+      'write' permission.
+    */
+
     if (!MY_S_ISREG(f_stat.st_mode) ||
         !(f_stat.st_mode & MY_S_IWRITE))
       goto err;
+
+    return 0;
   }
-  else
-  {
-    size_t path_length;
+
+  /* Get dirname of the file path. */
+  (void) dirname_part(path, log_file_str, &path_length);
+
+  /* Dirname is empty if file path is relative. */
+  if (!path_length)
+    return 0;
+
   /*
-      Check if directory exists and 
-      we have permission to create file & write to file
+    Check if directory exists and we have permission to create file and
+    write to file.
   */
-    (void) dirname_part(path, log_file_str, &path_length);
   if (my_access(path, (F_OK|W_OK)))
     goto err;
-  }
+
   return 0;
 
 err: