MDEV-22380: Assertion `name.length == strlen(name.str)' failed ...bb-10.3-bar-MDEV-22380

Also fixes:
MDEV-25399 Assertion `name.length == strlen(name.str)' failed in Item_func_sp::make_send_field

Also fixes a problem that in this scenario:

SET NAMES binary;
SELECT 'some not well-formed utf8 string';

the auto-generated column name copied the binary string value directly
to the Item name, without checking utf8 well-formedness.

After this change auto-generated column names work as follows:
- Zero bytes 0x00 are copied to the name using HEX notation
- In case of "SET NAMES binary", all bytes sequences that do not make
  well-formed utf8 characters are copied to the name using HEX notation.

1 files changed, 76 insertions, 20 deletions

diff --git a/sql/item.cc b/sql/item.cc
index c79e706d875..1319d5c4b62 100644
--- a/sql/item.cc
+++ b/sql/item.cc
@@ -1217,6 +1217,80 @@ bool Item::check_type_scalar(const char *opname) const
 }
 
 
+extern "C" {
+
+/*
+  All values greater than MY_NAME_BINARY_VALUE are
+  interpreted as binary bytes.
+  The exact constant value does not matter,
+  but it must be greater than 0x10FFFF,
+  which is the maximum possible character in Unicode.
+*/
+#define MY_NAME_BINARY_VALUE 0x200000
+
+/*
+  Print all binary bytes as well as zero character U+0000 in hex notation.
+  Print other characters normally.
+*/
+static int
+my_wc_mb_item_name(CHARSET_INFO *cs, my_wc_t wc, uchar *str, uchar *end)
+{
+  if (wc == 0 || wc >= MY_NAME_BINARY_VALUE)
+  {
+    if (str + 4 >= end)
+      return MY_CS_TOOSMALL3;
+    str[0]= '\\';
+    str[1]= 'x';
+    str[2]= _dig_vec_upper[(uchar) (wc >> 4)];
+    str[3]= _dig_vec_upper[(uchar) wc & 0x0F];
+    return 4;
+  }
+  return my_charset_utf8_handler.wc_mb(cs, wc, str, end);
+}
+
+
+/*
+  Scan characters and mark all illegal sequences as binary byte values,
+  to have my_wc_mb_utf8_escape_name() print them using HEX notation.
+*/
+static int
+my_mb_wc_item_name(CHARSET_INFO *cs, my_wc_t *pwc,
+                   const uchar *str, const uchar *end)
+{
+  int rc= cs->cset->mb_wc(cs, pwc, str, end);
+  if (rc == MY_CS_ILSEQ)
+  {
+    *pwc= MY_NAME_BINARY_VALUE + *str;
+    return 1;
+  }
+  return rc;
+}
+
+}
+
+
+static LEX_CSTRING
+make_name(THD *thd,
+          const char *str, size_t length, CHARSET_INFO *cs,
+          size_t max_octet_length)
+{
+  uint errors;
+  size_t dst_nbytes= length * system_charset_info->mbmaxlen;
+  set_if_smaller(dst_nbytes, max_octet_length);
+  char *dst= (char*) thd->alloc(dst_nbytes + 1);
+  if (!dst)
+    return null_clex_str;
+  uint32 cnv_length= my_convert_using_func(dst, dst_nbytes, system_charset_info,
+                                           my_wc_mb_item_name,
+                                           str, length,
+                                           cs == &my_charset_bin ?
+                                             system_charset_info : cs,
+                                           my_mb_wc_item_name, &errors);
+  dst[cnv_length]= '\0';
+  return Lex_cstring(dst, cnv_length);
+}
+
+
 void Item::set_name(THD *thd, const char *str, size_t length, CHARSET_INFO *cs)
 {
   if (!length)
@@ -1267,32 +1341,14 @@ void Item::set_name(THD *thd, const char *str, size_t length, CHARSET_INFO *cs)
                           ER_REMOVED_SPACES, ER_THD(thd, ER_REMOVED_SPACES),
                           buff);
   }
-  if (!my_charset_same(cs, system_charset_info))
-  {
-    size_t res_length;
-    name.str= sql_strmake_with_convert(thd, str, length, cs,
-                                       MAX_ALIAS_NAME, system_charset_info,
-                                       &res_length);
-    name.length= res_length;
-  }
-  else
-    name.str= thd->strmake(str, (name.length= MY_MIN(length,MAX_ALIAS_NAME)));
+  name= make_name(thd, str, length, cs, MAX_ALIAS_NAME - 1);
 }
 
 
 void Item::set_name_no_truncate(THD *thd, const char *str, uint length,
                                 CHARSET_INFO *cs)
 {
-  if (!my_charset_same(cs, system_charset_info))
-  {
-    size_t res_length;
-    name.str= sql_strmake_with_convert(thd, str, length, cs,
-                                       UINT_MAX, system_charset_info,
-                                       &res_length);
-    name.length= res_length;
-  }
-  else
-    name.str= thd->strmake(str, (name.length= length));
+  name= make_name(thd, str, length, cs, UINT_MAX - 1);
 }