Segmentation Fault SQLite Backup - c++

Question

I want to backup the SQLite database from my file system to in memory database using C++. I read this website and try the example 1. It compiled perfectly but I get an error "Segmentation Fault". The code looks like this:
Ps: The last line printf("foo1"); is not printed
#include <stdio.h>
#include <sqlite3.h>
#include <nlohmann/json.hpp>
using namespace std;
using json = nlohmann::json;
static int callback(void *NotUsed, int count, char **data, char **column) {
int i;
int lastEntry = count - 1;
printf("{");
for (i=0; i<count; i++) {
if (i == lastEntry ) {
printf("\"%s\" : \"%s\"", column[i], data[i] ? data[i] : "NULL");
} else {
printf("\"%s\" : \"%s\",", column[i], data[i] ? data[i] : "NULL");
}
}
printf("}\n");
return 0;
}
int loadOrSaveDb(sqlite3 *pFile, const char *zFilename, int isSave){
int rc; /* Function return code */
sqlite3 *pInMemory; /* Database connection opened on zFilename */
sqlite3_backup *pBackup; /* Backup object used to copy data */
sqlite3 *pTo; /* Database to copy to (pFile or pInMemory) */
sqlite3 *pFrom; /* Database to copy from (pFile or pInMemory) */
/* Open the database file identified by zFilename. Exit early if this fails
** for any reason. */
rc = sqlite3_open(zFilename, &pFile);
if( rc==SQLITE_OK ){
pFrom = (isSave ? pInMemory : pFile);
pTo = (isSave ? pFile : pInMemory);
pBackup = sqlite3_backup_init(pTo, "main", pFrom, "main");
if( pBackup ){
(void)sqlite3_backup_step(pBackup, -1);
(void)sqlite3_backup_finish(pBackup);
}
printf("foo");
rc = sqlite3_errcode(pTo);
}
/* Close the database connection opened on database file zFilename
** and return the result of this function. */
(void)sqlite3_close(pFile);
return rc;
}
int main(int argc, char* argv[]) {
sqlite3 *db;
char *zErrMsg = 0;
int rc;
string sql;
/* Open Database */
rc = sqlite3_open("test.db", &db);
if( rc ) {
fprintf(stderr, "Can't open database: %s\n", sqlite3_errmsg(db));
return(0);
} else {
fprintf(stderr, "Opened database successfully\n");
}
/* Create SQL Statement */
sql = "CREATE TABLE COMPANY(" \
"ID INT PRIMARY KEY NOT NULL," \
"name TEXT NOT NULL," \
"AGE INT NOT NULL," \
"ADDRESS CHAR(50)," \
"SALARY REAL );";
/* Execute SQL statement */
rc = sqlite3_exec(db, sql.c_str(), callback, 0, &zErrMsg);
if( rc != SQLITE_OK ){
fprintf(stderr, "SQL error: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
} else {
fprintf(stdout, "Table created successfully\n");
}
/* Insert SQL statement */
sql = "INSERT INTO COMPANY " \
"VALUES (1, 'Paul', 32, 'California', 20000.00 ); " \
"INSERT INTO COMPANY " \
"VALUES (2, 'Allen', 25, 'Texas', 15000.00 ); " \
"INSERT INTO COMPANY " \
"VALUES (3, 'Teddy', 23, 'Norway', 20000.00 );" \
"INSERT INTO COMPANY " \
"VALUES (4, 'Mark', 25, 'Rich-Mond ', 65000.00 );";
/* Execute SQL statement */
rc = sqlite3_exec(db, sql.c_str(), callback, 0, &zErrMsg);
if( rc != SQLITE_OK ){
fprintf(stderr, "SQL error: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
} else {
fprintf(stdout, "Records created successfully\n");
}
/* Select SQL statement */
//sql = "SELECT * from COMPANY WHERE NAME LIKE 'Paul'";
sql = "SELECT * from COMPANY";
/* Execute SQL statement */
rc = sqlite3_exec(db, sql.c_str(), callback, 0, &zErrMsg);
if( rc != SQLITE_OK ) {
fprintf(stderr, "SQL error: %s\n", zErrMsg);
sqlite3_free(zErrMsg);
} else {
fprintf(stdout, "Operation done successfully\n");
}
loadOrSaveDb(db, "test.db", 0);
sqlite3_close(db);
printf("foo1");
return 0;
}

Answer 1

The destination for sqlite3_backup_init has to be a database connection handle. In order to use sqlite3 *pInMemory; as the destination, you should initialise it with such a handle:
sqlite3 *pInMemory; /* Database connection opened on zFilename */
sqlite3_open(":memory:", &pInMemory);