Fix for bug #31069: crash in 'sounds like'

and for bug #31070: crash during conversion of charsets

Problem: passing a 0 byte length string to some my_mb_wc_XXX() 
functions leads to server crash due to improper argument check.

Fix: properly check arguments passed to my_mb_wc_XXX() functions.

mysql-test/include/ctype_common.inc

@@ -51,6 +51,15 @@ SELECT c1 as want1result  from t1 where c1 like 'locatio%';
 SELECT c1 as want1result  from t1 where c1 like 'location%';
 DROP TABLE t1;
 
+#
+# Bug #31070: crash during conversion of charsets
+#
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+select a sounds like a from t1;
+drop table t1;
+
 DROP DATABASE d1;
 # Restore settings
 USE test;

mysql-test/r/ctype_big5.result

@@ -52,6 +52,17 @@ SELECT c1 as want1result  from t1 where c1 like 'location%';
 want1result
 location
 DROP TABLE t1;
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+cast(a as char(1))
+
+
+select a sounds like a from t1;
+a sounds like a
+1
+1
+drop table t1;
 DROP DATABASE d1;
 USE test;
 SET character_set_server= @safe_character_set_server;

mysql-test/r/ctype_euckr.result

@@ -52,6 +52,17 @@ SELECT c1 as want1result  from t1 where c1 like 'location%';
 want1result
 location
 DROP TABLE t1;
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+cast(a as char(1))
+
+
+select a sounds like a from t1;
+a sounds like a
+1
+1
+drop table t1;
 DROP DATABASE d1;
 USE test;
 SET character_set_server= @safe_character_set_server;

mysql-test/r/ctype_gb2312.result

@@ -52,6 +52,17 @@ SELECT c1 as want1result  from t1 where c1 like 'location%';
 want1result
 location
 DROP TABLE t1;
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+cast(a as char(1))
+
+
+select a sounds like a from t1;
+a sounds like a
+1
+1
+drop table t1;
 DROP DATABASE d1;
 USE test;
 SET character_set_server= @safe_character_set_server;

mysql-test/r/ctype_gbk.result

@@ -52,6 +52,17 @@ SELECT c1 as want1result  from t1 where c1 like 'location%';
 want1result
 location
 DROP TABLE t1;
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+cast(a as char(1))
+
+
+select a sounds like a from t1;
+a sounds like a
+1
+1
+drop table t1;
 DROP DATABASE d1;
 USE test;
 SET character_set_server= @safe_character_set_server;

mysql-test/r/ctype_uca.result

@@ -2371,6 +2371,17 @@ SELECT c1 as want1result  from t1 where c1 like 'location%';
 want1result
 location
 DROP TABLE t1;
+create table t1 (a set('a') not null);
+insert into t1 values (),();
+select cast(a as char(1)) from t1;
+cast(a as char(1))
+
+
+select a sounds like a from t1;
+a sounds like a
+1
+1
+drop table t1;
 DROP DATABASE d1;
 USE test;
 SET character_set_server= @safe_character_set_server;

strings/ctype-big5.c

@@ -6256,12 +6256,12 @@ my_mb_wc_big5(CHARSET_INFO *cs __attribute__((unused)),
 	      my_wc_t *pwc,const uchar *s,const uchar *e)
 {
 
-  int hi=s[0];
+  int hi;
   
   if (s >= e)
     return MY_CS_TOOSMALL;
   
-  if (hi<0x80)
+  if ((hi= s[0]) < 0x80)
   {
     pwc[0]=hi;
     return 1;

strings/ctype-cp932.c

@@ -5352,12 +5352,12 @@ my_wc_mb_cp932(CHARSET_INFO *cs  __attribute__((unused)),
 static int 
 my_mb_wc_cp932(CHARSET_INFO *cs  __attribute__((unused)),
 	      my_wc_t *pwc, const uchar *s, const uchar *e){
-  int hi=s[0];
+  int hi;
   
   if (s >= e)
     return MY_CS_TOOSMALL;
   
-  if (hi < 0x80)
+  if ((hi= s[0]) < 0x80)
   {
     pwc[0]=hi;
     return 1;

strings/ctype-euc_kr.c

@@ -8614,12 +8614,12 @@ my_mb_wc_euc_kr(CHARSET_INFO *cs __attribute__((unused)),
 		 my_wc_t *pwc, const uchar *s, const uchar *e)
 {
   
-  int hi=s[0];
+  int hi;
   
   if (s >= e)
     return MY_CS_TOOSMALL;
   
-  if (hi<0x80)
+  if ((hi= s[0]) < 0x80)
   {
     pwc[0]=hi;
     return 1;

strings/ctype-gb2312.c

@@ -5665,12 +5665,10 @@ my_mb_wc_gb2312(CHARSET_INFO *cs  __attribute__((unused)),
 		my_wc_t *pwc, const uchar *s, const uchar *e){
   int hi;
   
-  hi=(int) s[0];
-  
   if (s >= e)
     return MY_CS_TOOSMALL;
   
-  if (hi<0x80)
+  if ((hi= s[0]) < 0x80)
   {
     pwc[0]=hi;
     return 1;

strings/ctype-sjis.c

@@ -4512,12 +4512,12 @@ mb:
 static int 
 my_mb_wc_sjis(CHARSET_INFO *cs  __attribute__((unused)),
 	      my_wc_t *pwc, const uchar *s, const uchar *e){
-  int hi=s[0];
+  int hi;
   
   if (s >= e)
     return MY_CS_TOOSMALL;
   
-  if (hi < 0x80)
+  if ((hi= s[0]) < 0x80)
   {
     pwc[0]=hi;
     return 1;