MDEV-30713 field length handling for CONNECT engine

fp->field_length was unsigned and therefore the negative
condition around it.

Backport of cc182aca93 fixes it, however to correct the
consistent use of types pcf->Length needs to be unsigned
too.

At one point pcf->Precision is assigned from pcf->Length so
that's also unsigned.

GetTypeSize is assigned to length and has a length argument.
A -1 default value seemed dangerious to case, so at least 0
should assert if every hit.

storage/connect/catalog.h

@@ -39,9 +39,9 @@ typedef struct _colinfo {
   PCSZ   Name;
   int    Type;
   int    Offset;
-  int    Length;
+  unsigned    Length;
   int    Key;
-  int    Precision;
+  unsigned    Precision;
   int    Scale;
   int    Opt;
   int    Freq;

storage/connect/ha_connect.cc

@@ -1618,10 +1618,7 @@ void *ha_connect::GetColumnOption(PGLOBAL g, void *field, PCOLINFO pcf)
   pcf->Scale= 0;
   pcf->Opt= (fop) ? (int)fop->opt : 0;
 
-	if (fp->field_length >= 0)
   pcf->Length= fp->field_length;
-	else
-		pcf->Length= 256;            // BLOB?
 
   pcf->Precision= pcf->Length;
 

storage/connect/tabext.cpp

@@ -466,7 +466,7 @@ bool TDBEXT::MakeSQL(PGLOBAL g, bool cnt)
 
 	if (Quote) {
 		// Tabname can have both database and table identifiers, we need to parse
-		if (res= strstr(buf, "."))
+		if ((res= strstr(buf, ".")))
 		{
 			// Parse schema
 			my_len= res - buf + 1;

storage/connect/value.cpp

@@ -163,7 +163,7 @@ PCSZ GetTypeName(int type)
 /***********************************************************************/
 /*  GetTypeSize: returns the PlugDB internal type size.                */
 /***********************************************************************/
-int GetTypeSize(int type, int len)
+unsigned GetTypeSize(int type, unsigned len)
 {
   switch (type) {
     case TYPE_DECIM:
@@ -176,7 +176,7 @@ int GetTypeSize(int type, int len)
     case TYPE_DOUBLE: len = sizeof(double);     break;
     case TYPE_TINY:   len = sizeof(char);       break;
     case TYPE_PCHAR:  len = sizeof(char*);      break;
-    default:          len = -1;
+    default:          len = 0;
   } // endswitch type
 
   return len;

storage/connect/value.h

@@ -41,7 +41,7 @@ typedef struct _datpar *PDTP;         // For DTVAL
 /***********************************************************************/
 // Exported functions
 DllExport PCSZ  GetTypeName(int);
-DllExport int   GetTypeSize(int, int);
+DllExport unsigned   GetTypeSize(int, unsigned);
 #ifdef ODBC_SUPPORT
 /* This function is exported for use in OEM table type DLLs */
 DllExport int   TranslateSQLType(int stp, int prec,