Make status of NO_BACKSLASH_ESCAPES mode known to the client so

it can use it to switch to only quoting apostrophes by doubling
them when it is in effect. (Bug #10214)

include/my_sys.h

@@ -865,6 +865,9 @@ extern void add_compiled_collation(CHARSET_INFO *cs);
 extern ulong escape_string_for_mysql(CHARSET_INFO *charset_info,
                                      char *to, ulong to_length,
                                      const char *from, ulong length);
+extern ulong escape_quotes_for_mysql(CHARSET_INFO *charset_info,
+                                     char *to, ulong to_length,
+                                     const char *from, ulong length);
 
 extern void thd_increment_bytes_sent(ulong length);
 extern void thd_increment_bytes_received(ulong length);

include/mysql_com.h

@@ -148,6 +148,7 @@ enum enum_server_command
 */
 #define SERVER_STATUS_LAST_ROW_SENT 128
 #define SERVER_STATUS_DB_DROPPED        256 /* A database was dropped */
+#define SERVER_STATUS_NO_BACKSLASH_ESCAPES 512
 
 #define MYSQL_ERRMSG_SIZE	512
 #define NET_READ_TIMEOUT	30		/* Timeout on read */

libmysql/libmysql.c

@@ -1615,9 +1615,16 @@ mysql_escape_string(char *to,const char *from,ulong length)
 ulong STDCALL
 mysql_real_escape_string(MYSQL *mysql, char *to,const char *from,
 			 ulong length)
+{
+  if (mysql->server_status & SERVER_STATUS_NO_BACKSLASH_ESCAPES)
+  {
+    return escape_quotes_for_mysql(mysql->charset, to, 0, from, length);
+  }
+  else
   {
     return escape_string_for_mysql(mysql->charset, to, 0, from, length);
   }
+}
 
 
 char * STDCALL

mysys/charset.c

@@ -656,3 +656,67 @@ ulong escape_string_for_mysql(CHARSET_INFO *charset_info,
   return overflow ? (ulong)~0 : (ulong) (to - to_start);
 }
 
+
+/*
+  NOTE
+    to be consistent with escape_string_for_mysql(), to_length may be 0 to
+    mean "big enough"
+  RETURN
+    the length of the escaped string or ~0 if it did not fit.
+*/
+ulong escape_quotes_for_mysql(CHARSET_INFO *charset_info,
+                              char *to, ulong to_length,
+                              const char *from, ulong length)
+{
+  const char *to_start= to;
+  const char *end, *to_end=to_start + (to_length ? to_length-1 : 2*length);
+  my_bool overflow=0;
+#ifdef USE_MB
+  my_bool use_mb_flag= use_mb(charset_info);
+#endif
+  for (end= from + length; from < end; from++)
+  {
+    char escape=0;
+#ifdef USE_MB
+    int tmp_length;
+    if (use_mb_flag && (tmp_length= my_ismbchar(charset_info, from, end)))
+    {
+      if (to + tmp_length > to_end)
+      {
+        overflow=1;
+        break;
+      }
+      while (tmp_length--)
+	*to++= *from++;
+      from--;
+      continue;
+    }
+    /*
+      We don't have the same issue here with a non-multi-byte character being
+      turned into a multi-byte character by the addition of an escaping
+      character, because we are only escaping the ' character with itself.
+     */
+#endif
+    if (*from == '\'')
+    {
+      if (to + 2 > to_end)
+      {
+        overflow=1;
+        break;
+      }
+      *to++= '\'';
+      *to++= '\'';
+    }
+    else
+    {
+      if (to + 1 > to_end)
+      {
+        overflow=1;
+        break;
+      }
+      *to++= *from;
+    }
+  }
+  *to= 0;
+  return overflow ? (ulong)~0 : (ulong) (to - to_start);
+}

sql/set_var.cc

@@ -3238,7 +3238,16 @@ void fix_sql_mode_var(THD *thd, enum_var_type type)
     global_system_variables.sql_mode=
       fix_sql_mode(global_system_variables.sql_mode);
   else
+  {
     thd->variables.sql_mode= fix_sql_mode(thd->variables.sql_mode);
+    /*
+      Update thd->server_status
+     */
+    if (thd->variables.sql_mode & MODE_NO_BACKSLASH_ESCAPES)
+      thd->server_status|= SERVER_STATUS_NO_BACKSLASH_ESCAPES;
+    else
+      thd->server_status&= ~SERVER_STATUS_NO_BACKSLASH_ESCAPES;
+  }
 }
 
 /* Map database specific bits to function bits */

sql/sql_class.cc

@@ -282,6 +282,8 @@ void THD::init(void)
 #endif
   pthread_mutex_unlock(&LOCK_global_system_variables);
   server_status= SERVER_STATUS_AUTOCOMMIT;
+  if (variables.sql_mode & MODE_NO_BACKSLASH_ESCAPES)
+    server_status|= SERVER_STATUS_NO_BACKSLASH_ESCAPES;
   options= thd_startup_options;
   open_options=ha_open_options;
   update_lock_default= (variables.low_priority_updates ?

tests/mysql_client_test.c

@@ -13332,6 +13332,35 @@ static void test_bug9992()
   mysql_close(mysql1);
 }
 
+
+/*
+  Check that the server signals when NO_BACKSLASH_ESCAPES mode is in effect,
+  and mysql_real_escape_string() does the right thing as a result.
+*/
+
+static void test_bug10214()
+{
+  MYSQL_RES* res ;
+  int   len;
+  char  out[8];
+
+  myheader("test_bug10214");
+
+  DIE_UNLESS(!(mysql->server_status & SERVER_STATUS_NO_BACKSLASH_ESCAPES));
+
+  len= mysql_real_escape_string(mysql, out, "a'b\\c", 5);
+  DIE_UNLESS(memcmp(out, "a\\'b\\\\c", len) == 0);
+
+  mysql_query(mysql, "set sql_mode='NO_BACKSLASH_ESCAPES'");
+  DIE_UNLESS(mysql->server_status & SERVER_STATUS_NO_BACKSLASH_ESCAPES);
+
+  len= mysql_real_escape_string(mysql, out, "a'b\\c", 5);
+  DIE_UNLESS(memcmp(out, "a''b\\c", len) == 0);
+
+  mysql_query(mysql, "set sql_mode=''");
+}
+
+
 /*
   Read and parse arguments and MySQL options from my.cnf
 */
@@ -13567,6 +13596,7 @@ static struct my_tests_st my_tests[]= {
   { "test_bug10729", test_bug10729 },
   { "test_bug11111", test_bug11111 },
   { "test_bug9992", test_bug9992 },
+  { "test_bug10214", test_bug10214 },
   { 0, 0 }
 };