Syntax error in MySQL prepare statement using C API - mysql

Question

I created a MySQL database, with some stored procedures. Using MySQL Workbench the SP forks fine, and now I need to launch them using a c program.
I created the program, which connect successfully to my db, and I'm able to launch procedures which not requires parameters.
To launch more complex procedure I need to use the prepare statement in c: in particular, I want to call the procedure esame_cancella(IN code CHAR(5)) which deletes a selected row of the table 'esame'.
int status;
MYSQL_RES *result;
MYSQL_ROW row;
MYSQL_FIELD *field;
MYSQL_RES *rs_metadata;
MYSQL_STMT *stmt;
MYSQL_BIND ps_params[6];
unsigned long length[6];
char cod[64];
printf("Codice: ");
scanf ("%s",cod);
length[0] = strlen(cod);
stmt = mysql_stmt_init(conn);
if (stmt == NULL) {
printf("Could not initialize statement\n");
exit(1);
}
status = mysql_stmt_prepare(stmt, "call esame_cancella(?) ", 64);
test_stmt_error(stmt, status); //line which gives me the syntax error
memset(ps_params, 0, sizeof(ps_params));
ps_params[0].buffer_type = MYSQL_TYPE_VAR_STRING;
ps_params[0].buffer = cod;
ps_params[0].buffer_length = 64;
ps_params[0].length = &length[0];
ps_params[0].is_null = 0;
// bind parameters
status = mysql_stmt_bind_param(stmt, ps_params); //muore qui
test_stmt_error(stmt, status);
// Run the stored procedure
status = mysql_stmt_execute(stmt);
test_stmt_error(stmt, status);
}
I use test_stmt_error to see MySQL log calling procedures.
static void test_stmt_error(MYSQL_STMT * stmt, int status)
{
if (status) {
fprintf(stderr, "Error: %s (errno: %d)\n",
mysql_stmt_error(stmt), mysql_stmt_errno(stmt));
exit(1);
}
}
when I compile, and launch my program, I have the following log:
Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '' at line 1 (errno: 1064)
Any help?

Answer 1

It looks like the string length being passed to mysql_stmt_prepare is wrong - try changing the 64 to 24.
Or better yet, try something like:
const char sql_sp[] = "call esame_cancella(?) ";
...
status = mysql_stmt_prepare(stmt, sql_sp, sizeof(sql_sp));