LnRSoft | "Promoting passion for software development"

How to temporarily disable IPv6 on Ubuntu? You need to diagnose a communication issue or track down a network problem?

By Roland Ihasz / 28th June 2018 29th June 2018 / Linux / Disable IPv6, IPv6, ubuntu

IPv6 provides solution of the IPv4 address exhaustion as it’s offering a much larger addressing space.
However, there are few instances in which IPv6 is casing network problems.
Some hardware doesn’t utilize it or take any advantages of IPv6 communications protocol. There are instances in which the temporary and easy solution is to (permanently) disable it. It can be easily re-enabled when it needed again.

In case you need to disable it, either only for troubleshooting or permanently, you can use the following terminal commands.

First of all, let’s verify the current status of your IPv6 communications protocol.

$ cat /proc/sys/net/ipv6/conf/all/disable_ipv6

1	$ cat /proc/sys/net/ipv6/conf/all/disable_ipv6

If this command returns 0 that means IPv6 is enabled in your system.

$ sudo vim /etc/sysctl.d/99-sysctl.conf

1	$ sudo vim /etc/sysctl.d/99-sysctl.conf

Scroll down to the end of the file and insert these three lines below.

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

net.ipv6.conf.all.disable_ipv6 = 1

net.ipv6.conf.default.disable_ipv6 = 1

net.ipv6.conf.lo.disable_ipv6 = 1

Save and quit your editor, then reboot your system.

Verifying the status of IPv6.

$ cat /proc/sys/net/ipv6/conf/all/disable_ipv6

1	$ cat /proc/sys/net/ipv6/conf/all/disable_ipv6

This command should return 1 meaning you successfully disabled IPv6 communications protocol.

To re-enable IPv6 just simple delete or comment out those 3 lines above.

You can use

sudo sysctl -p

1	sudo sysctl -p

to read values from file, it should return:

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.lo.disable_ipv6 = 1

net.ipv6.conf.all.disable_ipv6 = 1

net.ipv6.conf.default.disable_ipv6 = 1

net.ipv6.conf.lo.disable_ipv6 = 1

There are some additional commands if this method does not work.

Disable the network manager

$ sudo service network-manager stop

1	$ sudo service network-manager stop

Get the IP address from the server using:

$ sudo dhclient enp2s1

1	$ sudo dhclient enp2s1

List of IP address

$ ip address show dev enp2s1

1	$ ip address show dev enp2s1

Removing all IP information from an interface (enp2s1 in my case)

$ sudo ip addr flush
$ sudo ip addr flush dev enp2s1

1 2	$ sudo ip addr flush $ sudo ip addr flush dev enp2s1

Assign the first ip addresses like this:

$ sudo ip addr add 192.168.1.123/24 dev enp2s1

1	$ sudo ip addr add 192.168.1.123/24 dev enp2s1

You can repeat for other IP addresses.
You can add the default route using:

$ sudo route add default gw internet gateway ip address

1	$ sudo route add default gw internet gateway ip address

List of network devices:

$ sudo lshw -short -class network

1	$ sudo lshw -short -class network

Restart the networking.service

$ sudo systemctl restart networking.service

1	$ sudo systemctl restart networking.service

$ sudo /etc/init.d/networking restart

1	$ sudo /etc/init.d/networking restart

Ipv6 test is a free online service to diagnose connection problems: http://ipv6-test.com/

SQLite – How to use fundamental functions in C++

By Roland Ihasz / 19th June 2018 28th July 2018 / C++, C++ Libraries (Cross-platform), Database Design & Development, Software Development / C++, C++17, SQLite, sqlite3

SQLite operations in C++

This tutorial aimed to demonstrate how to use SQLite database operations such as CREATE, INSERT, UPDATE, SELECT and DELETE in C++. Since the appearance first smartphone and other mobile devices SQLite become most widely deployed and used database engine in the world. Precise numbers are difficult to obtain but SQLite is likely used more than all other database engines combined. We can find SQLite in every Android device, iPhone and iOS device, Mac, Windows10, Firefox, Chrome, Safari, Skype, Dropbox, TurboTax, QuickBooks, PHP, Python, television sets, set-top cable boxes and many automotive multimedia systems.

It’s an open-source SQL database engine. You can download the source code or precompiled binaries depending your requirements. You might also need to add [-lsqlite3] and [-std=c++17] to successfully compile, create an executable file. Each of the following source code available on my git repository.

github.com/lnrsoft/sqlite3_cpp_basics_updated
or
lnrrepo.ddns.net/git/lnrsoft/sqlite3_cpp_basics_updated

Use this link local_db.sqlite (5 downloads) if you would like to download the local_db.sqlite file that I used in this tutorial.

Step 1 – The first thing we need to do is to create the actual database file that we will use in this article. I called sqltdemo.db in our case.

#include <iostream>
#include <sqlite3.h>
#include <string>

int main() {
    sqlite3* db;
    auto op = sqlite3_open("local_db.sqlite", &db);
    auto cl = sqlite3_close(db);
    if(op) {
	std::cerr << "SQLite ERROR: " << sqlite3_errmsg(db) << std::endl;
	return (0);
    } else {
	std::cout << "SQLite local db has been opened successfully."
	          << std::endl;
    }
    if(cl) {
	std::cerr << "SQLite ERROR: " << sqlite3_errmsg(db) << std::endl;
	return (0);
    } else {
	std::cout << "SQLite local db has been closed successfully."
	          << std::endl;
    }
}

#include <iostream>

#include <sqlite3.h>

#include <string>

int main() {

sqlite3* db;

auto op = sqlite3_open("local_db.sqlite", &db);

auto cl = sqlite3_close(db);

if(op) {

std::cerr << "SQLite ERROR: " << sqlite3_errmsg(db) << std::endl;

return (0);

} else {

std::cout << "SQLite local db has been opened successfully."

<< std::endl;

}

if(cl) {

std::cerr << "SQLite ERROR: " << sqlite3_errmsg(db) << std::endl;

return (0);

} else {

std::cout << "SQLite local db has been closed successfully."

<< std::endl;

}

Compile and run our source code to create the local_db.sqlite with the following command. Here we link our code with the sqlite3 library that will create our db file.

$ clang++ 01_openDB.cpp -Wall -Wextra -lsqlite3 -std=c++17
$ ./a.out
SQLite local db has been opened successfully.
SQLite local db has been closed successfully.

$ clang++ 01_openDB.cpp -Wall -Wextra -lsqlite3 -std=c++17

$ ./a.out

SQLite local db has been opened successfully.

SQLite local db has been closed successfully.

Verify our result:

$ ls -la
-rw-r--r--   1 rolandihasz staff   605 Mar  1 21:05 01_openDB.cpp
-rw-r--r--   1 rolandihasz staff 21606 Mar  1 21:06 local_db.sqlite
-rwxr-xr-x   1 rolandihasz staff  8660 Mar  1 21:06 a.out

$ ls -la

-rw-r--r-- 1 rolandihasz staff 605 Mar 1 21:05 01_openDB.cpp

-rw-r--r-- 1 rolandihasz staff 21606 Mar 1 21:06 local_db.sqlite

-rwxr-xr-x 1 rolandihasz staff 8660 Mar 1 21:06 a.out

Step 2 – CREATE TABLE

#include <iostream>
#include <sqlite3.h>
#include <string>

static int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
    int i;
    for(i = 0; i < argc; i++) {
        std::cerr << azColName[i] << argv[i] << argv[i] << "NULL";
    }
    std::cout << std::endl;
    return 0;
}

int main()
{
    sqlite3 *db;
    char *zErrMsg = nullptr;
    const char *sql;
    auto rc = sqlite3_open("local_db.sqlite", &db);
    if(rc) {
        std::cerr << "Failed open database: " << sqlite3_errmsg(db)
                  << std::endl;
        return (0);
    }
    else {
        std::cerr << "Database successfully opened" << std::endl;
    }
    sql = "CREATE TABLE CANDIDATE("
          "ID INT PRIMARY KEY     NOT NULL,"
          "NAME           TEXT    NOT NULL,"
          "AGE            INT     NOT NULL,"
          "ROLE           TEXT    NOT NULL,"
          "SALARY         TEXT    NOT NULL);";
    rc = sqlite3_exec(db, sql, callback, nullptr, &zErrMsg);
    if(rc != SQLITE_OK) {
        std::cerr << "SQL error: " << zErrMsg << std::endl;
        sqlite3_free(&zErrMsg);
    }
    else {
        std::cerr << "Table successfully created" << std::endl;
    }
    sqlite3_close(db);
    return 0;
}

#include <iostream>

#include <sqlite3.h>

#include <string>

static int callback(void *NotUsed, int argc, char **argv, char **azColName)

{

int i;

for(i = 0; i < argc; i++) {

std::cerr << azColName[i] << argv[i] << argv[i] << "NULL";

}

std::cout << std::endl;

return 0;

}

int main()

{

sqlite3 *db;

char *zErrMsg = nullptr;

const char *sql;

auto rc = sqlite3_open("local_db.sqlite", &db);

if(rc) {

std::cerr << "Failed open database: " << sqlite3_errmsg(db)

<< std::endl;

return (0);

}

else {

std::cerr << "Database successfully opened" << std::endl;

}

sql = "CREATE TABLE CANDIDATE("

"ID INT PRIMARY KEY NOT NULL,"

"NAME TEXT NOT NULL,"

"AGE INT NOT NULL,"

"ROLE TEXT NOT NULL,"

"SALARY TEXT NOT NULL);";

rc = sqlite3_exec(db, sql, callback, nullptr, &zErrMsg);

if(rc != SQLITE_OK) {

std::cerr << "SQL error: " << zErrMsg << std::endl;

sqlite3_free(&zErrMsg);

}

else {

std::cerr << "Table successfully created" << std::endl;

}

sqlite3_close(db);

return 0;

}

Compile and run.

$ clang++ 02_sqlite3_create_table.cpp -Wall -Wextra -lsqlite3 -std=c++17
$ ./a.out
Database successfully opened
Table successfully created

$ clang++ 02_sqlite3_create_table.cpp -Wall -Wextra -lsqlite3 -std=c++17

$ ./a.out

Database successfully opened

Table successfully created

Step 3 – INSERT INTO our CANDIDATE TABLE

#include <iostream>
#include <sqlite3.h>
#include <string>

static int callback(void *NotUsed, int argc, char **argv, char **azColName)
{
    int i;
    for(i = 0; i < argc; i++) {
        std::cerr << azColName[i] << argv[i] << argv[i] << "NULL";
    }
    std::cout << std::endl;
    return 0;
}
int main()
{
    sqlite3 *db;
    char *zErrMsg = nullptr;
    int rc;
    const char *sql;
    rc = sqlite3_open("local_db.sqlite", &db);
    if(rc) {
        std::cerr << "Failed open database: " << sqlite3_errmsg(db)
                  << std::endl;
        return (0);
    }
    else {
        std::cerr << "Database successfully opened" << std::endl;
    }
    sql = "INSERT INTO CANDIDATE (ID,NAME,AGE,ROLE,SALARY) "
          "VALUES (1, 'Daniel', 29, 'CCO', 130000 ); "
          "INSERT INTO CANDIDATE (ID,NAME,AGE,ROLE,SALARY) "
          "VALUES (2, 'Roland', 35, 'CTO', 175000 ); "
          "INSERT INTO CANDIDATE (ID,NAME,AGE,ROLE,SALARY)"
          "VALUES (3, 'Leslie', 33, 'CEO', 200000 );";
    rc = sqlite3_exec(db, sql, callback, nullptr, &zErrMsg);
    if(rc != SQLITE_OK) {
        std::cerr << "SQL error: " << zErrMsg << std::endl;
        sqlite3_free(zErrMsg);
    }
    else {
        std::cerr << "Records created successfully" << std::endl;
    }
    sqlite3_close(db);
    return 0;
}

#include <iostream>

#include <sqlite3.h>

#include <string>

static int callback(void *NotUsed, int argc, char **argv, char **azColName)

{

int i;

for(i = 0; i < argc; i++) {

std::cerr << azColName[i] << argv[i] << argv[i] << "NULL";

}

std::cout << std::endl;

return 0;

}

int main()

{

sqlite3 *db;

char *zErrMsg = nullptr;

int rc;

const char *sql;

rc = sqlite3_open("local_db.sqlite", &db);

if(rc) {

std::cerr << "Failed open database: " << sqlite3_errmsg(db)

<< std::endl;

return (0);

}

else {

std::cerr << "Database successfully opened" << std::endl;

}

sql = "INSERT INTO CANDIDATE (ID,NAME,AGE,ROLE,SALARY) "

"VALUES (1, 'Daniel', 29, 'CCO', 130000 ); "

"INSERT INTO CANDIDATE (ID,NAME,AGE,ROLE,SALARY) "

"VALUES (2, 'Roland', 35, 'CTO', 175000 ); "

"INSERT INTO CANDIDATE (ID,NAME,AGE,ROLE,SALARY)"

"VALUES (3, 'Leslie', 33, 'CEO', 200000 );";

rc = sqlite3_exec(db, sql, callback, nullptr, &zErrMsg);

if(rc != SQLITE_OK) {

std::cerr << "SQL error: " << zErrMsg << std::endl;

sqlite3_free(zErrMsg);

}

else {

std::cerr << "Records created successfully" << std::endl;

}

sqlite3_close(db);

return 0;

}

Compile and run.

$ clang++ 03_sqlite3_insert.cpp -Wall -Wextra -lsqlite3 -std=c++17
$ ./a.out
Database successfully opened
Records created successfully

$ clang++ 03_sqlite3_insert.cpp -Wall -Wextra -lsqlite3 -std=c++17

$ ./a.out

Database successfully opened

Records created successfully

Step 4 – Fetch and display records from the company CANDIDATE TABLE. In this scenario we use a callback function that obtains results from SELECT statement.

//callback function declaration
typedef int (*sqlite3_callback)(
   void*,    /* Data provided in the 4th argument of sqlite3_exec() */
   int,      /* The number of columns in row */
   char**,   /* An array of strings representing fields in the row */
   char**    /* An array of strings representing column names */
);

//callback function declaration

typedef int (*sqlite3_callback)(

void*, /* Data provided in the 4th argument of sqlite3_exec() */

int, /* The number of columns in row */

char**, /* An array of strings representing fields in the row */

char** /* An array of strings representing column names */

);

#include <iostream>
#include <sqlite3.h>
#include <stdio.h>
#include <stdlib.h>
#include <string>

static int callback(void *data, int argc, char **argv, char **azColName)
{
    fprintf(stderr, "\nCallback function call: ", &data);
    for(auto i = 0; i < argc; i++) {
        printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");
    }
    return 0;
}

int main()
{
    sqlite3 *db;
    char *zErrMsg = nullptr;
    int rc;
    const char *sql;
    const char *data = "Callback function call";
    rc = sqlite3_open("local_db.sqlite", &db);
    if(rc) {
        std::cerr << "Failed open database: " << sqlite3_errmsg(db)
                  << std::endl;
        return (0);
    }
    else {
        std::cerr << "Database successfully opened" << std::endl;
    }
    sql = "SELECT * from CANDIDATE";
    rc = sqlite3_exec(db, sql, callback, &data, &zErrMsg);
    if(rc != SQLITE_OK) {
        std::cerr << "SQL error: " << zErrMsg << std::endl;
        sqlite3_free(zErrMsg);
    }
    else {
        std::cout << "\nExecution completed successfully" << std::endl;
    }
    sqlite3_close(db);
    return 0;
}

#include <iostream>

#include <sqlite3.h>

#include <stdio.h>

#include <stdlib.h>

#include <string>

static int callback(void *data, int argc, char **argv, char **azColName)

{

fprintf(stderr, "\nCallback function call: ", &data);

for(auto i = 0; i < argc; i++) {

printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");

}

return 0;

}

int main()

{

sqlite3 *db;

char *zErrMsg = nullptr;

int rc;

const char *sql;

const char *data = "Callback function call";

rc = sqlite3_open("local_db.sqlite", &db);

if(rc) {

std::cerr << "Failed open database: " << sqlite3_errmsg(db)

<< std::endl;

return (0);

}

else {

std::cerr << "Database successfully opened" << std::endl;

}

sql = "SELECT * from CANDIDATE";

rc = sqlite3_exec(db, sql, callback, &data, &zErrMsg);

if(rc != SQLITE_OK) {

std::cerr << "SQL error: " << zErrMsg << std::endl;

sqlite3_free(zErrMsg);

}

else {

std::cout << "\nExecution completed successfully" << std::endl;

}

sqlite3_close(db);

return 0;

}

Compile and run.

$ clang++ 04_sqlite3_select_operation.cpp -Wall -Wextra -lsqlite3 -std=c++17
$ ./a.out
Database successfully opened

Callback function call: ID = 1
NAME = Daniel
AGE = 29
ROLE = CCO
SALARY = 130000

Callback function call: ID = 2
NAME = Roland
AGE = 35
ROLE = CTO
SALARY = 175000

Callback function call: ID = 3
NAME = Leslie
AGE = 33
ROLE = CEO
SALARY = 200000

Execution completed successfully

$ clang++ 04_sqlite3_select_operation.cpp -Wall -Wextra -lsqlite3 -std=c++17

$ ./a.out

Database successfully opened

Callback function call: ID = 1

NAME = Daniel

AGE = 29

ROLE = CCO

SALARY = 130000

Callback function call: ID = 2

NAME = Roland

AGE = 35

ROLE = CTO

SALARY = 175000

Callback function call: ID = 3

NAME = Leslie

AGE = 33

ROLE = CEO

SALARY = 200000

Execution completed successfully

Step 5 – Using UPDATE statement to update any records in our CANDIDATE table.

#include <iostream>
#include <sqlite3.h>
#include <stdio.h>
#include <stdlib.h>
#include <string>

static int callback(void *data, int argc, char **argv, char **azColName)
{
    fprintf(stderr, "\nCallback function call: ", &data);
    for(auto i = 0; i < argc; i++) {
        printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");
    }
    return 0;
}

int main()
{
    sqlite3 *db;
    char *zErrMsg = nullptr;
    int rc;
    const char *sql;
    const char *data = "Callback function call";
    rc = sqlite3_open("local_db.sqlite", &db);
    if(rc) {
        std::cerr << "Failed open database: " << sqlite3_errmsg(db)
                  << std::endl;
        return (0);
    }
    else {
        std::cout << "Database successfully opened" << std::endl;
    }
    sql = "UPDATE CANDIDATE set SALARY = 150000 where ID=1; "
          "SELECT * from CANDIDATE";
    rc = sqlite3_exec(db, sql, callback, &data, &zErrMsg);
    if(rc != SQLITE_OK) {
        std::cerr << "SQL error: " << zErrMsg << std::endl;
        sqlite3_free(zErrMsg);
    }
    else {
        std::cout << "Execution completed successfully" << std::endl;
    }
    sqlite3_close(db);
    return 0;
}

#include <iostream>

#include <sqlite3.h>

#include <stdio.h>

#include <stdlib.h>

#include <string>

static int callback(void *data, int argc, char **argv, char **azColName)

{

fprintf(stderr, "\nCallback function call: ", &data);

for(auto i = 0; i < argc; i++) {

printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");

}

return 0;

}

int main()

{

sqlite3 *db;

char *zErrMsg = nullptr;

int rc;

const char *sql;

const char *data = "Callback function call";

rc = sqlite3_open("local_db.sqlite", &db);

if(rc) {

std::cerr << "Failed open database: " << sqlite3_errmsg(db)

<< std::endl;

return (0);

}

else {

std::cout << "Database successfully opened" << std::endl;

}

sql = "UPDATE CANDIDATE set SALARY = 150000 where ID=1; "

"SELECT * from CANDIDATE";

rc = sqlite3_exec(db, sql, callback, &data, &zErrMsg);

if(rc != SQLITE_OK) {

std::cerr << "SQL error: " << zErrMsg << std::endl;

sqlite3_free(zErrMsg);

}

else {

std::cout << "Execution completed successfully" << std::endl;

}

sqlite3_close(db);

return 0;

}

Compile and run.

$ clang++ 05_sqlite3_update_operation.cpp -Wall -Wextra -lsqlite3 -std=c++17
$ ./a.out
Database successfully opened

Callback function call: ID = 1

NAME = Daniel
AGE = 29
ROLE = CCO
SALARY = 150000

Callback function call: ID = 2
NAME = Roland
AGE = 35
ROLE = CTO
SALARY = 175000

Callback function call: ID = 3
NAME = Leslie
AGE = 33
ROLE = CEO
SALARY = 200000

Execution completed successfully

$ clang++ 05_sqlite3_update_operation.cpp -Wall -Wextra -lsqlite3 -std=c++17

$ ./a.out

Database successfully opened

Callback function call: ID = 1

NAME = Daniel

AGE = 29

ROLE = CCO

SALARY = 150000

Callback function call: ID = 2

NAME = Roland

AGE = 35

ROLE = CTO

SALARY = 175000

Callback function call: ID = 3

NAME = Leslie

AGE = 33

ROLE = CEO

SALARY = 200000

Execution completed successfully

Step 6 – DELETE statement can delete any records from the CANDIDATE table.

#include <iostream>
#include <sqlite3.h>
#include <stdio.h>
#include <stdlib.h>
#include <string>

static int callback(void *data, int argc, char **argv, char **azColName)
{
    fprintf(stderr, "\nCallback function call: ", &data);
    for(auto i = 0; i < argc; i++) {
        printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");
    }
    return 0;
}

int main()
{
    sqlite3 *db;
    char *zErrMsg = nullptr;
    int rc;
    const char *sql;
    const char *data = "Callback function call";
    rc = sqlite3_open("local_db.sqlite", &db);
    if(rc) {
        std::cerr << "Failed open database: " << sqlite3_errmsg(db)
                  << std::endl;
        return (0);
    }
    else {
        std::cerr << "Database successfully opened" << std::endl;
    }
    sql = "DELETE from CANDIDATE where ID=2; "
          "SELECT * from CANDIDATE";
    rc = sqlite3_exec(db, sql, callback, &data, &zErrMsg);
    if(rc != SQLITE_OK) {
        std::cerr << "SQL error: " << zErrMsg << std::endl;
        sqlite3_free(zErrMsg);
    }
    else {
        std::cout << "\nExecution completed successfully" << std::endl;
    }
    sqlite3_close(db);
    return 0;
}

#include <iostream>

#include <sqlite3.h>

#include <stdio.h>

#include <stdlib.h>

#include <string>

static int callback(void *data, int argc, char **argv, char **azColName)

{

fprintf(stderr, "\nCallback function call: ", &data);

for(auto i = 0; i < argc; i++) {

printf("%s = %s\n", azColName[i], argv[i] ? argv[i] : "NULL");

}

return 0;

}

int main()

{

sqlite3 *db;

char *zErrMsg = nullptr;

int rc;

const char *sql;

const char *data = "Callback function call";

rc = sqlite3_open("local_db.sqlite", &db);

if(rc) {

std::cerr << "Failed open database: " << sqlite3_errmsg(db)

<< std::endl;

return (0);

}

else {

std::cerr << "Database successfully opened" << std::endl;

}

sql = "DELETE from CANDIDATE where ID=2; "

"SELECT * from CANDIDATE";

rc = sqlite3_exec(db, sql, callback, &data, &zErrMsg);

if(rc != SQLITE_OK) {

std::cerr << "SQL error: " << zErrMsg << std::endl;

sqlite3_free(zErrMsg);

}

else {

std::cout << "\nExecution completed successfully" << std::endl;

}

sqlite3_close(db);

return 0;

}

Compile and run.

$ clang++ 06_sqlite3_delete_operation.cpp -Wall -Wextra -lsqlite3 -std=c++17
$ ./a.out
Database successfully opened

Callback function call: ID = 1
NAME = Daniel
AGE = 29
ROLE = CCO
SALARY = 150000

Callback function call: ID = 3
NAME = Leslie
AGE = 33
ROLE = CEO
SALARY = 200000

Execution completed successfully

$ clang++ 06_sqlite3_delete_operation.cpp -Wall -Wextra -lsqlite3 -std=c++17

$ ./a.out

Database successfully opened

Callback function call: ID = 1

NAME = Daniel

AGE = 29

ROLE = CCO

SALARY = 150000

Callback function call: ID = 3

NAME = Leslie

AGE = 33

ROLE = CEO

SALARY = 200000

Execution completed successfully

I recommend you to check the official SQLite documentation at sqlite.org for more advance SQLite features and options and support. For further info about using sql with c++ you might found it useful to read me previous post of a simple Qt tool to test QSqlDatabase access connection to a MySQL database. I created this simple Qt command line tool to test connection between Qt client applications and a remote Mysql Server. The code includes Secure Sockets Layer (SSL) support to test secure connection. The QSqlDatabase class provides an interface for accessing a database through a connection where an instance of QSqlDatabase represents the connection. The connection provides access to the database via one of the supported database drivers, which are derived from QSqlDriver.

Alternatively, we can subclass your own database driver from QSqlDriver. My next post will be an article how to write your own database driver in Qt for Unix, OSX and Windows platforms.

Install Java SE Development Kit 10.0.1 on Ubuntu 18.04 LTS x64

By Roland Ihasz / 28th May 2018 28th June 2018 / Linux, Software Development / Install Java, Install jdk 10, Oracle, Ubuntu 18.04

Download: jdk-10.0.1_linux-x64_bin.tar.gz

$ tar -xvf jdk-*.tar.gz
$ sudo mkdir -p /usr/lib/jvm/jdk-10.0.1/
$ sudo mv jdk-10.0.1*/* /usr/lib/jvm/jdk-10.0.1/
$ sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk-10.0.1/bin/java" 1010
$ sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk-10.0.1/bin/javac" 1010
$ sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk-10.0.1/bin/javaws" 1010

$ tar -xvf jdk-*.tar.gz

$ sudo mkdir -p /usr/lib/jvm/jdk-10.0.1/

$ sudo mv jdk-10.0.1*/* /usr/lib/jvm/jdk-10.0.1/

$ sudo update-alternatives --install "/usr/bin/java" "java" "/usr/lib/jvm/jdk-10.0.1/bin/java" 1010

$ sudo update-alternatives --install "/usr/bin/javac" "javac" "/usr/lib/jvm/jdk-10.0.1/bin/javac" 1010

$ sudo update-alternatives --install "/usr/bin/javaws" "javaws" "/usr/lib/jvm/jdk-10.0.1/bin/javaws" 1010

$ sudo vim /etc/profile.d/javajdk.sh

1	$ sudo vim /etc/profile.d/javajdk.sh

export J2SDKDIR=/usr/lib/jvm/jdk-10.0.1
export J2REDIR=/usr/lib/jvm/jdk-10.0.1/jre
export PATH=$PATH:/usr/lib/jvm/jdk-10.0.1/bin:/usr/lib/jvm/jdk-10.0.1/db/bin:/usr/lib/jvm/jdk-10.0.1/jre/bin
export JAVA_HOME=/usr/lib/jvm/jdk-10.0.1
export DERBY_HOME=/usr/lib/jvm/jdk-10.0.1/db

export J2SDKDIR=/usr/lib/jvm/jdk-10.0.1

export J2REDIR=/usr/lib/jvm/jdk-10.0.1/jre

export PATH=$PATH:/usr/lib/jvm/jdk-10.0.1/bin:/usr/lib/jvm/jdk-10.0.1/db/bin:/usr/lib/jvm/jdk-10.0.1/jre/bin

export JAVA_HOME=/usr/lib/jvm/jdk-10.0.1

export DERBY_HOME=/usr/lib/jvm/jdk-10.0.1/db

$ source /etc/profile.d/javajdk.sh

1	$ source /etc/profile.d/javajdk.sh

You might need to reboot your system.

$ java –version
java version "10.0.1" 2018-04-17
Java(TM) SE Runtime Environment 18.3 (build 10.0.1+10)
Java HotSpot(TM) 64-Bit Server VM 18.3 (build 10.0.1+10, mixed mode)

$ java –version

java version "10.0.1" 2018-04-17

Java(TM) SE Runtime Environment 18.3 (build 10.0.1+10)

Java HotSpot(TM) 64-Bit Server VM 18.3 (build 10.0.1+10, mixed mode)

[C++] Working with Protocol Buffer

By Roland Ihasz / 27th May 2018 20th June 2018 / C++, Software Development / Protocol Buffer

The following tutorial provides a basic C++ programmer’s introduction to working with protocol buffers.

[C++] Helgrind – the thread error detector

By Roland Ihasz / 27th April 2018 20th June 2018 / C++, Software Development, Static Code Analyzers / Helgrind, Valgrind

Helgrind is a Valgrind tool for detecting synchronisation errors in C, C++ and Fortran programs that use the POSIX pthreads threading primitives. To use this tool, you must specify --tool=helgrind on the Valgrind command line.

[C++] MemorySanitizer

By Roland Ihasz / 27th March 2018 20th June 2018 / C++, Software Development / MemorySanitizer

MemorySanitizer is a detector of uninitialized memory reads in C/C++ programs. Uninitialized values occur when stack- or heap-allocated memory is read before it is written. MSan detects cases where such values affect program execution.
At this time, MemorySanitizer supports Linux x86_64 only.
To use MemorySanitizer, compile and link your program with -fsanitize=memory -fPIE -pie. To get any stack traces, add -fno-omit-frame-pointer.

#include <stdio.h>

int main(int argc, char** argv) {
  int* a = new int[10];
  a[5] = 0;
  if (a[argc])
    printf("xx\n");
  return 0;
}

#include <stdio.h>

int main(int argc, char** argv) {

int* a = new int[10];

a[5] = 0;

if (a[argc])

printf("xx\n");

return 0;

}

$ clang++  -fsanitize=memory -fPIE -pie -fno-omit-frame-pointer -g -O2 umr.cpp 
$ ./a.out 
==32154==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x5650c17c9bb1  (/home/lnrsoft/a.out+0x89bb1)
    #1 0x7fc3c6ba382f  (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
    #2 0x5650c175a478  (/home/lnrsoft/a.out+0x1a478)

SUMMARY: MemorySanitizer: use-of-uninitialized-value (/home/lnrsoft/a.out+0x89bb1) 
Exiting

$ clang++ -fsanitize=memory -fPIE -pie -fno-omit-frame-pointer -g -O2 umr.cpp

$ ./a.out

==32154==WARNING: MemorySanitizer: use-of-uninitialized-value

#0 0x5650c17c9bb1 (/home/lnrsoft/a.out+0x89bb1)

#1 0x7fc3c6ba382f (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

#2 0x5650c175a478 (/home/lnrsoft/a.out+0x1a478)

SUMMARY: MemorySanitizer: use-of-uninitialized-value (/home/lnrsoft/a.out+0x89bb1)

Exiting

Origins tracking

$ clang++ -fsanitize=memory -fsanitize-memory-track-origins -fPIE -pie -fno-omit-frame-pointer -g -O2 umr.cpp 
$ ./a.out 
==32080==WARNING: MemorySanitizer: use-of-uninitialized-value
    #0 0x558203e37c26  (/home/lnrsoft/a.out+0x89c26)
    #1 0x7f3b148c782f  (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)
    #2 0x558203dc84a8  (/home/lnrsoft/a.out+0x1a4a8)

  Uninitialized value was created by a heap allocation
    #0 0x558203e359b0  (/home/lnrsoft/a.out+0x879b0)
    #1 0x558203e37b83  (/home/lnrsoft/a.out+0x89b83)
    #2 0x7f3b148c782f  (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

SUMMARY: MemorySanitizer: use-of-uninitialized-value (/home/lnrsoft/a.out+0x89c26) 
Exiting

$ clang++ -fsanitize=memory -fsanitize-memory-track-origins -fPIE -pie -fno-omit-frame-pointer -g -O2 umr.cpp

$ ./a.out

==32080==WARNING: MemorySanitizer: use-of-uninitialized-value

#0 0x558203e37c26 (/home/lnrsoft/a.out+0x89c26)

#1 0x7f3b148c782f (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

#2 0x558203dc84a8 (/home/lnrsoft/a.out+0x1a4a8)

Uninitialized value was created by a heap allocation

#0 0x558203e359b0 (/home/lnrsoft/a.out+0x879b0)

#1 0x558203e37b83 (/home/lnrsoft/a.out+0x89b83)

#2 0x7f3b148c782f (/lib/x86_64-linux-gnu/libc.so.6+0x2082f)

SUMMARY: MemorySanitizer: use-of-uninitialized-value (/home/lnrsoft/a.out+0x89c26)

Exiting

[C++] AddressSanitizer

By Roland Ihasz / 27th February 2018 20th June 2018 / C++, Software Development / AddressSanitizer

AddressSanitizer is a memory error detector for C/C++. It finds:

-Use after free (dangling pointer dereference)
-Heap buffer overflow
-Stack buffer overflow
-Global buffer overflow
-Use after return
-Use after scope
-Initialization order bugs
-Memory leaks

In order to use AddressSanitizer we will need to compile and link your program using clang with the -fsanitize=address switch. To get a reasonable performance add -O1 or higher.

#include <stdlib.h>
int main() {
  char *x = (char*)malloc(10 * sizeof(char*));
  free(x);
  return x[5];
}

#include <stdlib.h>

int main() {

char *x = (char*)malloc(10 * sizeof(char*));

free(x);

return x[5];

}

$ clang++ -fsanitize=address -O1 -fno-omit-frame-pointer -g use-after-free.cpp
$ ./a.out
=================================================================
==36988==ERROR: AddressSanitizer: heap-use-after-free on address 0x607000000095 at pc 0x0001020bfef4 bp 0x7ffeedb409a0 sp 0x7ffeedb40998
READ of size 1 at 0x607000000095 thread T0
    #0 0x1020bfef3 in main use-after-free.cpp:5
    #1 0x7fff7e800114 in start (libdyld.dylib:x86_64+0x1114)

0x607000000095 is located 5 bytes inside of 80-byte region [0x607000000090,0x6070000000e0)
freed by thread T0 here:
    #0 0x10211d066 in wrap_free (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x59066)
    #1 0x1020bfeba in main use-after-free.cpp:4
    #2 0x7fff7e800114 in start (libdyld.dylib:x86_64+0x1114)

previously allocated by thread T0 here:
    #0 0x10211ce9c in wrap_malloc (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x58e9c)
    #1 0x1020bfeaf in main use-after-free.cpp:3
    #2 0x7fff7e800114 in start (libdyld.dylib:x86_64+0x1114)

SUMMARY: AddressSanitizer: heap-use-after-free use-after-free.cpp:5 in main
Shadow bytes around the buggy address:
  0x1c0dffffffc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1c0dffffffd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1c0dffffffe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1c0dfffffff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00
  0x1c0e00000000: fa fa fa fa 00 00 00 00 00 00 00 00 03 fa fa fa
=>0x1c0e00000010: fa fa[fd]fd fd fd fd fd fd fd fd fd fa fa fa fa
  0x1c0e00000020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c0e00000030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c0e00000040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c0e00000050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
  0x1c0e00000060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa
Shadow byte legend (one shadow byte represents 8 application bytes):
  Addressable:           00
  Partially addressable: 01 02 03 04 05 06 07 
  Heap left redzone:       fa
  Freed heap region:       fd
  Stack left redzone:      f1
  Stack mid redzone:       f2
  Stack right redzone:     f3
  Stack after return:      f5
  Stack use after scope:   f8
  Global redzone:          f9
  Global init order:       f6
  Poisoned by user:        f7
  Container overflow:      fc
  Array cookie:            ac
  Intra object redzone:    bb
  ASan internal:           fe
  Left alloca redzone:     ca
  Right alloca redzone:    cb
==36988==ABORTING
Abort trap: 6

$ clang++ -fsanitize=address -O1 -fno-omit-frame-pointer -g use-after-free.cpp

$ ./a.out

=================================================================

==36988==ERROR: AddressSanitizer: heap-use-after-free on address 0x607000000095 at pc 0x0001020bfef4 bp 0x7ffeedb409a0 sp 0x7ffeedb40998

READ of size 1 at 0x607000000095 thread T0

#0 0x1020bfef3 in main use-after-free.cpp:5

#1 0x7fff7e800114 in start (libdyld.dylib:x86_64+0x1114)

0x607000000095 is located 5 bytes inside of 80-byte region [0x607000000090,0x6070000000e0)

freed by thread T0 here:

#0 0x10211d066 in wrap_free (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x59066)

#1 0x1020bfeba in main use-after-free.cpp:4

#2 0x7fff7e800114 in start (libdyld.dylib:x86_64+0x1114)

previously allocated by thread T0 here:

#0 0x10211ce9c in wrap_malloc (libclang_rt.asan_osx_dynamic.dylib:x86_64h+0x58e9c)

#1 0x1020bfeaf in main use-after-free.cpp:3

#2 0x7fff7e800114 in start (libdyld.dylib:x86_64+0x1114)

SUMMARY: AddressSanitizer: heap-use-after-free use-after-free.cpp:5 in main

Shadow bytes around the buggy address:

0x1c0dffffffc0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

0x1c0dffffffd0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

0x1c0dffffffe0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

0x1c0dfffffff0: 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00

0x1c0e00000000: fa fa fa fa 00 00 00 00 00 00 00 00 03 fa fa fa

=>0x1c0e00000010: fa fa[fd]fd fd fd fd fd fd fd fd fd fa fa fa fa

0x1c0e00000020: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

0x1c0e00000030: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

0x1c0e00000040: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

0x1c0e00000050: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

0x1c0e00000060: fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa fa

Shadow byte legend (one shadow byte represents 8 application bytes):

Addressable: 00

Partially addressable: 01 02 03 04 05 06 07

Heap left redzone: fa

Freed heap region: fd

Stack left redzone: f1

Stack mid redzone: f2

Stack right redzone: f3

Stack after return: f5

Stack use after scope: f8

Global redzone: f9

Global init order: f6

Poisoned by user: f7

Container overflow: fc

Array cookie: ac

Intra object redzone: bb

ASan internal: fe

Left alloca redzone: ca

Right alloca redzone: cb

==36988==ABORTING

Abort trap: 6

[C++] ThreadSanitizer

By Roland Ihasz / 27th January 2018 16th March 2018 / C++, Software Development / clang, ThreadSanitizer

ThreadSanitizer is a data race detector for C/C++. Data races are one of the most common and hardest to debug types of bugs in concurrent systems.
Here is an example of a data race that can lead to crashes and memory corruptions:

#include <pthread.h>
#include <stdio.h>

int Global;

void *Thread1(void *x) {
  Global++;
  return NULL;
}

void *Thread2(void *x) {
  Global--;
  return NULL;
}

int main() {
  pthread_t t[2];
  pthread_create(&t[0], NULL, Thread1, NULL);
  pthread_create(&t[1], NULL, Thread2, NULL);
  pthread_join(t[0], NULL);
  pthread_join(t[1], NULL);
}

#include <pthread.h>

#include <stdio.h>

int Global;

void *Thread1(void *x) {

Global++;

return NULL;

}

void *Thread2(void *x) {

Global--;

return NULL;

}

int main() {

pthread_t t[2];

pthread_create(&t[0], NULL, Thread1, NULL);

pthread_create(&t[1], NULL, Thread2, NULL);

pthread_join(t[0], NULL);

pthread_join(t[1], NULL);

}

$ clang++ simple_race.cpp -fsanitize=thread -fPIE -pie -g
$ ./a.out

==================
WARNING: ThreadSanitizer: data race (pid=36804)
  Write of size 4 at 0x0001062b7068 by thread T2:
  * #0 Thread2(void*) simple_race.cpp:12 (a.out:x86_64+0x100000d8a)

  Previous write of size 4 at 0x0001062b7068 by thread T1:
  * #0 Thread1(void*) simple_race.cpp:7 (a.out:x86_64+0x100000d2a)

  Issue is caused by frames marked with "*".

  Location is global 'Global' at 0x0001062b7068 (a.out+0x000100001068)

  Thread T2 (tid=817154, running) created by main thread at:
    #0 pthread_create <null>:1600736 (libclang_rt.tsan_osx_dynamic.dylib:x86_64h+0x2a34d)
    #1 main simple_race.cpp:19 (a.out:x86_64+0x100000e07)

  Thread T1 (tid=817153, finished) created by main thread at:
    #0 pthread_create <null>:1600736 (libclang_rt.tsan_osx_dynamic.dylib:x86_64h+0x2a34d)
    #1 main simple_race.cpp:18 (a.out:x86_64+0x100000de8)

SUMMARY: ThreadSanitizer: data race simple_race.cpp:12 in Thread2(void*)
==================
ThreadSanitizer: reported 1 warnings
Abort trap: 6

$ clang++ simple_race.cpp -fsanitize=thread -fPIE -pie -g

$ ./a.out

==================

WARNING: ThreadSanitizer: data race (pid=36804)

Write of size 4 at 0x0001062b7068 by thread T2:

* #0 Thread2(void*) simple_race.cpp:12 (a.out:x86_64+0x100000d8a)

Previous write of size 4 at 0x0001062b7068 by thread T1:

* #0 Thread1(void*) simple_race.cpp:7 (a.out:x86_64+0x100000d2a)

Issue is caused by frames marked with "*".

Location is global 'Global' at 0x0001062b7068 (a.out+0x000100001068)

Thread T2 (tid=817154, running) created by main thread at:

#0 pthread_create <null>:1600736 (libclang_rt.tsan_osx_dynamic.dylib:x86_64h+0x2a34d)

#1 main simple_race.cpp:19 (a.out:x86_64+0x100000e07)

Thread T1 (tid=817153, finished) created by main thread at:

#0 pthread_create <null>:1600736 (libclang_rt.tsan_osx_dynamic.dylib:x86_64h+0x2a34d)

#1 main simple_race.cpp:18 (a.out:x86_64+0x100000de8)

SUMMARY: ThreadSanitizer: data race simple_race.cpp:12 in Thread2(void*)

==================

ThreadSanitizer: reported 1 warnings

Abort trap: 6

[C++] How to install gcc-7 on Ubuntu LTS 16.04

By Roland Ihasz / 29th December 2017 16th March 2018 / C++, Linux, Software Development / g++, g++-7, gcc, gcc-7

sudo apt-get update && \
sudo apt-get install build-essential software-properties-common -y && \
sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y && \
sudo apt-get update && \
sudo apt-get install gcc-snapshot -y && \
sudo apt-get update && \
sudo apt-get install gcc-7 g++-7 -y && \
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-7 60 --slave /usr/bin/g++ g++ /usr/bin/g++-7 && \
sudo apt-get install gcc-4.8 g++-4.8 -y && \
sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 60 --slave /usr/bin/g++ g++ /usr/bin/g++-4.8;

sudo apt-get update && \

sudo apt-get install build-essential software-properties-common -y && \

sudo add-apt-repository ppa:ubuntu-toolchain-r/test -y && \

sudo apt-get update && \

sudo apt-get install gcc-snapshot -y && \

sudo apt-get update && \

sudo apt-get install gcc-7 g++-7 -y && \

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-7 60 --slave /usr/bin/g++ g++ /usr/bin/g++-7 && \

sudo apt-get install gcc-4.8 g++-4.8 -y && \

sudo update-alternatives --install /usr/bin/gcc gcc /usr/bin/gcc-4.8 60 --slave /usr/bin/g++ g++ /usr/bin/g++-4.8;

[C++] Return absolute_path using boost::filesystem

By Roland Ihasz / 8th December 2017 3rd February 2018 / C++, Software Development / absolute path, boost, boost::filesystem

Return absolute_path using boost::filesystem

#include <boost/filesystem.hpp>
#include <iostream>

void info(const boost::filesystem::path &relative_path) {
    using namespace boost::filesystem;

    std::cout << "rel path: " << relative_path << '\n';
    std::cout << "cwd: " << current_path() << '\n'; // current working directory

    const path absolute_path = absolute(relative_path);
    std::cout << "absolute: " << absolute_path << '\n'
              << "root dir: " << absolute_path.root_directory() << '\n'
              << "root path: " << absolute_path.root_path() << '\n'
              << "parent dir: " << absolute_path.parent_path() << '\n'
              << "file name: " << absolute_path.filename() << '\n'
              << "-----------------------------------------------\n";
}

int main() {

    info("main.cpp"); // relative path

    boost::filesystem::path data_dir = "data/out/text";
    boost::filesystem::create_directories(data_dir);

    info(data_dir / "result.txt"); // relative path

    boost::filesystem::current_path(data_dir); // change cwd
    info("result.txt"); // relative path
}

#include <boost/filesystem.hpp>

#include <iostream>

void info(const boost::filesystem::path &relative_path) {

using namespace boost::filesystem;

std::cout << "rel path: " << relative_path << '\n';

std::cout << "cwd: " << current_path() << '\n'; // current working directory

const path absolute_path = absolute(relative_path);

std::cout << "absolute: " << absolute_path << '\n'

<< "root dir: " << absolute_path.root_directory() << '\n'

<< "root path: " << absolute_path.root_path() << '\n'

<< "parent dir: " << absolute_path.parent_path() << '\n'

<< "file name: " << absolute_path.filename() << '\n'

<< "-----------------------------------------------\n";

}

int main() {

info("main.cpp"); // relative path

boost::filesystem::path data_dir = "data/out/text";

boost::filesystem::create_directories(data_dir);

info(data_dir / "result.txt"); // relative path

boost::filesystem::current_path(data_dir); // change cwd

info("result.txt"); // relative path

}

Note:
You’ll need to add the boost libraries to the linking phase with the -L flag and the names of the libraries with the -l flag. This is different from the compilation phase where only the -I include path is needed. For example in my case:

$ clang++ ab_path.cpp -o ab_path -Wall -Wextra -std=c++1z -pedantic -L /usr/local/Cellar/boost/1.66.0/lib -lboost_system -lboost_filesystem

1	$ clang++ ab_path.cpp -o ab_path -Wall -Wextra -std=c++1z -pedantic -L /usr/local/Cellar/boost/1.66.0/lib -lboost_system -lboost_filesystem

boost::filesystem tutorials
https://meetingcpp.com/blog/items/handling-files-using-boost-filesystem.html
http://www.boost.org/doc/libs/1_55_0/libs/filesystem/doc/tutorial.html
http://www.boost.org/doc/libs/1_44_0/libs/filesystem/v3/doc/tutorial.html
http://www.boost.org/doc/libs/1_51_0/libs/filesystem/doc/reference.html#Absolute-path
http://www.boost.org/doc/libs/1_53_0/libs/filesystem/doc/reference.html
http://www.boost.org/doc/libs/1_55_0/libs/filesystem/doc/reference.html#copy_file
http://wiki.lihebi.com/boost.html

The Boost C++ Libraries
AdvC++Libs.key
boost-graph-library
asio_doc
dima-boost-intro
Boost_for_KDE_Developers-Volker_Krause

[C++] An Interesting Bit Array Example

By Roland Ihasz / 24th November 2017 9th December 2017 / C++ / bit array, C++

Here is an interesting bit array task and its solution in C++ that I thought it’s worth to share with you.
You are given four integers values: N, A, B, and C. You need to use them in order to create the sequence called bitArray with the following pseudo-code:

Task: calculate the number of distinct integer in the bitArray sequence.

Solution
Input: four space separated integers on a single line, N, A, B, and C respectively.
Where N = 32, A = 16, B = 16, C = 16.
Output: one integer that denotes the number of distinct integer in the bitArray sequence equals 7 as we set N, A, B, C values.

If you’d like to read the input from the console simply comment out line 57 and 62 and toggle comment selection on line 58, 59, 60 and 61.
Input read from the console:
four space separated integers on a single line, N, A, B, and C

respectively.
Output print to the console:
One integer that denotes the number of distinct integer in the sequence called bitArray.

#include <algorithm>
#include <iostream>

constexpr unsigned exp = 31; // exponent
constexpr unsigned twoToExp = 1u << exp;

int solve_b_even(unsigned int n, int a, int b, int c)
{
    if (b == 0) {
        if (a == c) {
            return 1;
        }
        return 2;
    }
    if (a == 0 && c == 0) {
        return 1;
    }
    int a1_minus_a0 = (b - 1) * a + c;
    int numr = exp - __builtin_popcount((a1_minus_a0 & -a1_minus_a0) - 1);
    int denomr = __builtin_popcount((b & -b) - 1);
    unsigned int m = numr / denomr + (numr % denomr == 0 ? 1 : 2);
    return std::min(m, n);
}

int solve_b_odd(unsigned int n, int a, int b, int c)
{
    if (b == 1) {
        return c == 0 ? 1 : std::min(n, twoToExp / (c & -c));
    }
    if (a == 0 && c == 0) {
        return 1;
    }
    unsigned int m = 1;
    int b_minus_1 = b - 1;
    int a1_minus_a0 = b_minus_1 * a + c;
    int b_to_m = b;
    int mask = (twoToExp * (b_minus_1 & -b_minus_1) /
            (a1_minus_a0 & -a1_minus_a0)) -
           1;
    while (m < n && (b_to_m & mask) != 1) {
        b_to_m = b_to_m * b_to_m;
        m = m * 2;
    }
    return std::min(m, n);
}

int solve(unsigned int n, int a, int b, int c)
{
    if (b % 2 == 0) {
        return solve_b_even(n, a, b, c);
    }
    return solve_b_odd(n, a, b, c);
}

int main()
{
    // int n, a, b, c;
    int n = 32;
    int a = 16;
    int b = 16;
    int c = 16;
    // std::cin >> n >> a >> b >> c;
    std::cout << solve(n, a, b, c);
    return 0;
}

#include <algorithm>

#include <iostream>

constexpr unsigned exp = 31; // exponent

constexpr unsigned twoToExp = 1u << exp;

int solve_b_even(unsigned int n, int a, int b, int c)

{

if (b == 0) {

if (a == c) {

return 1;

}

return 2;

}

if (a == 0 && c == 0) {

return 1;

}

int a1_minus_a0 = (b - 1) * a + c;

int numr = exp - __builtin_popcount((a1_minus_a0 & -a1_minus_a0) - 1);

int denomr = __builtin_popcount((b & -b) - 1);

unsigned int m = numr / denomr + (numr % denomr == 0 ? 1 : 2);

return std::min(m, n);

}

int solve_b_odd(unsigned int n, int a, int b, int c)

{

if (b == 1) {

return c == 0 ? 1 : std::min(n, twoToExp / (c & -c));

}

if (a == 0 && c == 0) {

return 1;

}

unsigned int m = 1;

int b_minus_1 = b - 1;

int a1_minus_a0 = b_minus_1 * a + c;

int b_to_m = b;

int mask = (twoToExp * (b_minus_1 & -b_minus_1) /

(a1_minus_a0 & -a1_minus_a0)) -

while (m < n && (b_to_m & mask) != 1) {

b_to_m = b_to_m * b_to_m;

m = m * 2;

}

return std::min(m, n);

}

int solve(unsigned int n, int a, int b, int c)

{

if (b % 2 == 0) {

return solve_b_even(n, a, b, c);

}

return solve_b_odd(n, a, b, c);

}

int main()

{

// int n, a, b, c;

int n = 32;

int a = 16;

int b = 16;

int c = 16;

// std::cin >> n >> a >> b >> c;

std::cout << solve(n, a, b, c);

return 0;

}

$ clang++ cpp_bit_array.cpp -o cpp_bit_array -Wall -Wextra -std=c++1z -pedantic
$ 7

1 2	$ clang++ cpp_bit_array.cpp -o cpp_bit_array -Wall -Wextra -std=c++1z -pedantic $ 7

The number of distinct integer in the sequence will be 536870912 when we change the previously set integer values to:

int n = -90000000;
int a = 160514480;
int b = 526178425;
int c = 1833883134;

$ clang++ cpp_bit_array.cpp -o cpp_bit_array -Wall -Wextra -std=c++1z -pedantic
$ 536870912

int n = -90000000;

int a = 160514480;

int b = 526178425;

int c = 1833883134;

$ clang++ cpp_bit_array.cpp -o cpp_bit_array -Wall -Wextra -std=c++1z -pedantic

$ 536870912

Use Wandbox online C++ compiler

[C++] cxx_status and support in Clang

By Roland Ihasz / 14th November 2017 9th December 2017 / C++ / -std=c++11, -std=c++14, -std=c++17, clang, cxx_status

Here is the list of current C++ implementation status and support in Clang as per Aug 2017.
You can find the complete list of features and minimum Clang version with support on the source page: https://clang.llvm.org/cxx_status.html

C++11 implementation status
Clang 3.3 and later implement all of the ISO C++ 2011 standard. By default, Clang builds C++ code according to the C++98 standard, with many C++11 features accepted as extensions. You can use Clang in C++11 mode with the -std=c++11 option. Clang’s C++11 mode can be used with libc++ or with gcc’s libstdc++.

C++14 implementation status
Clang 3.4 and later implement all of the ISO C++ 2014 standard.

You can use Clang in C++14 mode with the -std=c++14 option (use -std=c++1y in Clang 3.4 and earlier).

C++17 implementation status
Clang 5 and later implement all the features of the C++ 2017 Draft International Standard.
You can use Clang in C++17 mode with the -std=c++17 option (use -std=c++1z in Clang 4 and earlier).

C++2a implementation status
Clang has experimental support for some proposed features of the C++ standard following C++17, provisionally named C++2a. Note that support for these features may change or be removed without notice, as the draft C++2a standard evolves.
You can use Clang in C++2a mode with the -std=c++2a option.

More technical specifications and standing documents on the source page: https://clang.llvm.org/cxx_status.html