How handle UTF-8 encoding error in libpq?

Question

I have created this function to insert data into database:

void add_data_to_db(){
        const char *data[2][2] = {"2","e"};
        re = PQexecParams(connection,
                        "INSERT INTO test_table "\
                        "VALUES ($1, $2);",
                        2,NULL,data[2],NULL,NULL,0);
        if(PQresultStatus(re) != PGRES_TUPLES_OK){
                printf("%s\n", PQresultErrorMessage(re));
        }

        PQclear(re);
}

but when I run the program it prints :

ERROR:  invalid byte sequence for encoding "UTF8": 0x80

as far as I know this problem occurs when we have null value adding to table but I have not.

`data[2]` (in the function call) looks unusual to me; this is past the end of that array — Daniel Jour, Jul 01 '20 at 20:50
@DanielJour how can i mention the words or chars in array in this way? — Amir reza Riahi, Jul 01 '20 at 20:53

score 2 · Answer 1 · answered Jul 01 '20 at 20:59

According to the documentation the fifth argument of PQExecParams should be const char * const *paramValues ... so a pointer to constant pointers which point to constant char. The documentation specifies that it should point to an array of the specified (in the third argument) length (2 here).

data[2] is the third element of the data array (whoops, it has only two elements!).

data would decay to a pointer to the first element; that is a pointer to an array of two pointers which each point to a string. Exactly what you need.

score 1 · Accepted Answer · answered Jul 02 '20 at 06:46

1

It should be const char *data[2], and the function call should have data rather than data[2].

The error message means that PostgreSQL encountered bytes that are not part of a correctly encoded UTF-8 string.

answered Jul 02 '20 at 06:46

Laurenz Albe

209,280
17
206
263

I want to have an array of some strings, and then add them to database. if I can not create `data[n][n]` how can I do this? – Amir reza Riahi Jul 02 '20 at 07:41
2

Either `char data[2][2]` or `char *data[2]`, but not `char *data[2][2]`. – Laurenz Albe Jul 02 '20 at 07:47
I changed the line of defining `data` to `const char data[2][2]` and instead of using `data[2]` in fifth parameter, I used `data` but it still errors during the compile. – Amir reza Riahi Jul 04 '20 at 16:05
1

Since the errors are unknown to me, I cannot advise. – Laurenz Albe Jul 06 '20 at 05:26
now I have an array `char splitted_line[8][50];` and I used it have an error `note: expected ‘const char * const*’ but argument is of type ‘char (*)[50]’` and a warning `warning: passing argument 5 of ‘PQexecParams’ from incompatible pointer type [-Wincompatible-pointer-types] 99 | 8,NULL, splitted_line,NULL,NULL,0); ` thanks for helping. – Amir reza Riahi Jul 06 '20 at 12:43
1

Add a type cast. – Laurenz Albe Jul 06 '20 at 13:01
would you explain more? – Amir reza Riahi Jul 06 '20 at 13:15

How handle UTF-8 encoding error in libpq?

2 Answers2