Description:
------------
This relates to bug#25792, which has been marked Analyzed but does not seem to be fixed.

When retrieving data from a char() field containing multi-byte characters using e.g. odbc_fetch_into(), if the number of bytes used exceeds the number of characters then junk data is returned at the end of the string.

I have experience this with Postgres char columns when the database is created with e.g the EUC_CN character encoding(createdb -E EUC_CN).

This encoding uses between 1 and 3 bytes per character. So a char(10) could need up to 30 bytes. 

The problem is in the odbc_bindcols function in ext/odbc/php_odbc.c
  SQLColAttributes is called with SQL_COLUMN_DISPLAY_SIZE but this indicates the maximum number of characters required not the number of bytes.
This means the buffer allocated for the value may not be big enough
  result->values[i].value=(char)emalloc(displaysize+1);

Later on in e.g. odbc_fetch_into
  Z_STRLEN_P(tmp) = result->values[i].vallen;
  Z_STRVAL_P(tmp) = estrndup(result->values[i].value,Z_STRLEN_P(tmp));

This can result in a vallen bigger that displaysize. But the ODBC driver will only fill in at most displaysize+1 bytes(including null terminator). This means character data is missed and junk bytes are returned instead.

The same problem may exist in ext/pdo_odbc/odbc_stmt.c. Where 
  rc = SQLColAttribute(S->stmt, colno+1, SQL_DESC_DISPLAY_SIZE,
            NULL, 0, NULL, &displaysize);
is called. But I have not tested this.

The following fixes odbc_bindcols for the char(x) datatype. I believe 4 bytes is the maximum required for any character encoding.
php_odbc.c:line 988
      if (result->values[i].coltype == SQL_CHAR) {
        //If using a multibyte character encoding
        //number of bytes could be 4*SQL_COLUMN_DISPLAY_SIZE.
        //Without this workaround various functions
        //e.g. odbc_fetch_into will return data with a null after
        //diplaysize bytes and extra junk data at the end as
        //vallen can be bigger than displaysize. Tested using
        //PostgreSQL with EUC_CN encoding.
        displaysize*=4;
      }

The fix may be needed for other data types as well as SQL_CHAR.