Segfault submitting query - mysql

Question

I'm testing a wrapper library for the MySQL C API, and I'm trying to insert a row.
I've tested it in GDB, and the line (in my code) that faults appears as follows:
Breakpoint 1, cq_query (con=0x7fffffffe1c0,
query=0x6014a0 "INSERT INTO TaskType(state,parentID,displayName) VALUES(1,19,'boop')") at cqstatic.c:32
32 return mysql_query(con->con, query);
This query string is formatted correctly (I can paste it into the mysql command line, and it runs fine), so it would appear that something is wrong in the connection (con->con is of type void * cast to MYSQL *).
My other functions which do SELECT and UPDATE work fine. Only insert appears to be broken.
Here is my Test Code
#include <stdio.h>
#include <string.h>
#include <cquel.h>
int main(void)
{
struct dbconn con = cq_new_connection("myurl.tld",
"myuser", "mypasswd", "mydb");
cq_init(1024, 128);
char *fields[] = {
"state",
"parentID",
"displayName"
};
char *vals[] = {
"1",
"19",
"boop"
};
struct drow *row = cq_new_drow(3);
cq_drow_set(row, vals);
struct dlist *list = cq_new_dlist(3, fields, "");
cq_dlist_add(list, row);
cq_insert(con, "TaskType", list);
cq_free_dlist(list);
return 0;
}
Insert Function
int cq_insert(struct dbconn con, const char *table, const struct dlist *list)
{
int rc;
char *query, *columns, *values;
const char *fmt = "INSERT INTO %s(%s) VALUES(%s)";
if (table == NULL)
return 1;
if (list == NULL)
return 2;
query = calloc(CQ_QLEN, sizeof(char));
if (query == NULL)
return -1;
columns = calloc(CQ_QLEN/2, sizeof(char));
if (columns == NULL) {
free(query);
return -2;
}
values = calloc(CQ_QLEN/2, sizeof(char));
if (values == NULL) {
free(query);
free(columns);
return -3;
}
rc = cq_dlist_fields_to_utf8(&con, columns, CQ_QLEN/2, *list);
if (rc) {
free(query);
free(columns);
free(values);
return 100;
}
rc = cq_connect(&con);
if (rc) {
free(query);
free(columns);
free(values);
return 200;
}
for (struct drow *r = list->first; r != NULL; r = r->next) {
rc = cq_drow_to_utf8(&con, values, CQ_QLEN/2, *r);
if (rc)
break;
rc = snprintf(query, CQ_QLEN, fmt, table, columns, values);
if (CQ_QLEN <= (size_t) rc) {
rc = -4;
break;
}
rc = cq_query(&con, query);
if (rc) {
rc = 201;
break;
}
}
cq_close_connection(&con);
free(query);
free(columns);
free(values);
return rc;
}
And one of the important helper functions
int cq_fields_to_utf8(struct dbconn *con, char *buf, size_t buflen,
size_t fieldc, char * const *fieldnames, bool usequotes)
{
int rc = 0;
size_t num_left = fieldc, written = 0;
if (num_left == 0)
return 1;
char *temp = calloc(CQ_FMAXLEN+3, sizeof(char));
if (NULL == temp)
return -1;
char *field = calloc((CQ_FMAXLEN+3)*2+1, sizeof(char));
if (NULL == field) {
free(temp);
return -2;
}
/* prevent appending to buffer */
buf[0] = '\0';
cq_connect(con);
for (size_t i = 0; i < fieldc; ++i) {
bool escaped = fieldnames[i][0] == '\\';
const char *orig = escaped ? &fieldnames[i][1] : fieldnames[i];
const char *value;
bool isstr = false;
if (!escaped) {
mysql_real_escape_string(con->con, field, orig, strlen(orig));
value = field;
if (usequotes)
for (size_t j = 0; j < strlen(value); ++j) {
if (!isdigit(value[j])) {
isstr = true;
break;
}
}
} else {
value = orig;
}
const char *a = isstr ? "'" : "";
const char *c = --num_left > 0 ? "," : "";
written += snprintf(temp, CQ_FMAXLEN+3, "%s%s%s%s", a, value, a, c);
if (written >= buflen) {
rc = 2;
break;
}
strcat(buf, temp);
}
cq_close_connection(con);
free(field);
free(temp);
return rc;
}
used when setting up the query string.

Answer 1

Found my own issue. Blame the 10 minute rule.
I didn't look closely enough at cq_insert(), and it is making a double connection, closing the second one, leaving the first one lost, and the pointer pointing to freed memory, so segfault.