GECon2017_Cpp a monster that no one likes but that will outlast them all _Yauheni Akhotnikau

C++ ‒ a Monster
that no one likes
but that will outlast them all
Yauheni Akhotnikau

2
Started programming somewhere in 1990.
The first meet with C++ in 1991.
C++ is the main tool since 1992 with a few short pauses.
Used some other languages. For example: Pascal, Visual Basic, Java, Ruby, D,
Eiffel, Scala.
I can use C++ without a pain but I don't think that C++ is the greatest
language ever.
A few words about me

3
A bit of C++ evolution history.
Why C++ became popular and why C++ started to lose its popularity.
Why C++ is a Monster? If C ++ is a monster, then why does someone need
C++?
How to use C++ safely and efficiently?
Where and when C++ can be used. If it can...
Pressure to C++ from competitors. Real and imaginary.
Agenda

4
The history and evolution of C++
(and some taste of C++)

5
By the help of a simple demo application:
• there is a collection of struct place (each struct contains name, price and rating);
• sort this collection by rating, then by price, then by name. And then print the collection after
sorting;
• sort this collection by name, then print it.
A way to see the evolution in examples

6
Work on C++ began in 1979.
Bjarne Stroustrup decided to build a language with power of Simula 67 and
efficiency of C.
The first name of the new language was "C with Classes". Name C++
appeared in 1983.
The first public release in 1985.
The birth of C++

7
struct place {
char * name_;
long price_;
int rating_;
place() : name_(0) {}
place(const char * name, long price, int rating)
: name_(copy_name(name)), price_(price), rating_(rating) {}
place(const place & o)
: name_(copy_name(o.name_)), price_(o.price_), rating_(o.rating_) {}
~place() { delete[] name_; }
place & operator=(const place & o) {
char * copy = copy_name(o.name_);
delete[] name_;
name_ = copy; price_ = o.price_; rating_ = o.rating_;
return *this;
}
static char * copy_name(const char * src) {
char * r = 0;
if(src) {
r = new char[strlen(src) + 1];
strcpy(r, src);
}
return r;
}
};
A taste of ancient C++ (pre-C++98)

8
ostream & operator<<(ostream & to, const place & p) {
to << setw(20) << left << p.name_ << "[" << p.rating_ << "]"
<< setw(7) << right << p.price_;
return to;
}
void print(const place * places, size_t count) {
for(size_t i = 0; i != count; ++i)
cout << places[i] << endl;
cout << endl;
}

9
int compare_by_rating_price_name(const void * av, const void * bv) {
const place & a = *(const place *)av;
const place & b = *(const place *)bv;
int result;
if(a.rating_ < b.rating_) result = -1;
else {
if(a.rating_ == b.rating_) {
if(a.price_ < b.price_) result = -1;
else {
if(a.price_ == b.price_) {
result = strcmp(a.name_, b.name_);
}
else result = 1;
}
}
else result = 1;
}
return result;
}
int compare_by_name(const void * av, const void * bv) {
return strcmp(a.name_, b.name_);
}

10
void get_places(place *& places, size_t & count) {
places = new place[7];
places[0] = place("Moscow", 1500, 3);
places[1] = place("St. Petersburg", 1300, 5);
places[2] = place("Minsk", 500, 4);
places[3] = place("Tokyo", 3500, 4);
places[4] = place("Sydney", 5000, 3);
places[5] = place("Paris", 3000, 5);
places[6] = place("London", 3500, 4);
count = 7;
}

11
int main() {
place * places;
size_t count;
get_places(places, count);
qsort(places, count, sizeof(place), compare_by_rating_price_name);
print(places, count);
qsort(places, count, sizeof(place), compare_by_name);
delete[] places;
}

12
Moscow [3] 1500
Sydney [3] 5000
Minsk [4] 500
London [4] 3500
Tokyo [4] 3500
St. Petersburg [5] 1300
Paris [5] 3000
London [4] 3500
Minsk [4] 500
Moscow [3] 1500
Paris [5] 3000
St. Petersburg [5] 1300
Sydney [3] 5000
Tokyo [4] 3500

13
1985-1995: fast evolution:
– multiple inheritance, const-methods, protected keyword, namespaces, templates, exceptions,
RTTI, explicit keyword, ...
1990: ANSI/ISO standardization started.
1992: Alex Stepanov started STL.
1994-1998: process of inclusion of STL into the standard.
1998: the first international standard ‒ C++98.
2003: an updated standard ‒ C++03.
1985-2003: main milestones

14
using namespace std;
struct place {
string name_;
long price_;
int rating_;
place() {}
place(const char * name, float price, int rating)
: name_(name), price_(price), rating_(rating) {}
};
A taste of old C++ (C++98)

15
return to;
}
template<class C>
void print(const C & places) {
for(typename C::const_iterator i = places.begin(); i != places.end(); ++i)
cout << *i << endl;
cout << endl;
}

16
bool compare_by_rating_price_name(const place & a, const place & b) {
bool result = false;
if(a.rating_ < b.rating_) result = true;
else if(a.rating_ == b.rating_) {
if(a.price_ < b.price_) result = true;
else if(a.price_ == b.price_) result = (a.name_ < b.name_);
}
return result;
}
bool compare_by_name(const place & a, const place & b) {
return a.name_ < b.name_;
}

17
vector<place> get_places() {
vector<place> places;
places.push_back(place("Moscow", 1500, 3));
places.push_back(place("St. Petersburg", 1300, 5));
places.push_back(place("Minsk", 500, 4));
places.push_back(place("Tokyo", 3500, 4));
places.push_back(place("Sydney", 5000, 3));
places.push_back(place("Paris", 3000, 5));
places.push_back(place("London", 3500, 4));
return places;
}

18
int main() {
vector<place> places = get_places();
sort(places.begin(), places.end(), compare_by_rating_price_name);
print(places);
sort(places.begin(), places.end(), compare_by_name);
print(places);
}

19
2003-2011: long-term construction under the name of C++0x.
2011: C++11 released. It's a very different beast!
many, many language improvements;
significant extension of stdlib;
2014: C++14 released. A minor update with some very useful features.
2017: draft of C++17. An important update with lot of new features and
additions to stdlib.
2017: work on C++20 started.
2003-2017: main milestones

20
#include <fmt/format.h>
#include <fmt/ostream.h>
struct place {
string name_;
long price_;
int rating_;
};
A taste of modern C++ (C++17)

21
fmt::print(to, "{:<20}[{}]{:7}", p.name_, p.rating_, p.price_);
return to;
}
void print(auto & places) {
for(const auto & p : places)
cout << p << endl;
cout << endl;
}

22
return tie(a.rating_, a.price_, a.name_) < tie(b.rating_, b.price_, b.name_);
}
}

23
return {
{"Moscow", 1500, 3},
{"St. Petersburg", 1300, 5},
{"Minsk", 500, 4},
{"Tokyo", 3500, 4},
{"Sydney", 5000, 3},
{"Paris", 3000, 5},
{"London", 3500, 4}
};
}

24
int main() {
auto places = get_places();
sort(begin(places), end(places), compare_by_rating_price_name);
print(places);
sort(begin(places), end(places), compare_by_name);
print(places);
}

25
A short look to the full demo source code…
1985-2017: the comparison

26
#include <iostream.h>
#include <iomanip.h>
#include <string.h>
#include <stdlib.h>
struct place {
char * name_;
long price_;
int rating_;
place() : name_(0) {}
place(const char * name, long price, int rating)
: name_(copy_name(name)), price_(price), rating_(rating)
{}
place(const place & o)
: name_(copy_name(o.name_)), price_(o.price_),
rating_(o.rating_) {}
~place() {
delete[] name_;
}
place & operator=(const place & o) {
char * copy = copy_name(o.name_);
delete[] name_;
name_ = copy;
price_ = o.price_;
rating_ = o.rating_;
return *this;
}
static char * copy_name(const char * src) {
char * r = 0;
if(src) {
r = new char[strlen(src) + 1];
strcpy(r, src);
}
return r;
}
};
to << setw(20) << left << p.name_ << "[" << p.rating_ <<
"]"
return to;
}
void print(const place * places, size_t count) {
for(size_t i = 0; i != count; ++i)
cout << places[i] << endl;
cout << endl;
}
int compare_by_rating_price_name(const void * av, const
void * bv) {
int result;
if(a.rating_ < b.rating_) result = -1;
else {
if(a.rating_ == b.rating_) {
if(a.price_ < b.price_) result = -1;
else {
if(a.price_ == b.price_) {
result = strcmp(a.name_, b.name_);
}
else result = 1;
}
}
else result = 1;
}
return result;
}
int compare_by_name(const void * av, const void * bv) {
return strcmp(a.name_, b.name_);
}
void get_places(place *& places, size_t & count) {
places = new place[7];
places[0] = place("Moscow", 1500, 3);
places[1] = place("St. Petersburg", 1300, 5);
places[2] = place("Minsk", 500, 4);
places[3] = place("Tokyo", 3500, 4);
places[4] = place("Sydney", 5000, 3);
places[5] = place("Paris", 3000, 5);
places[6] = place("London", 3500, 4);
count = 7;
}
int main() {
place * places;
size_t count;
get_places(places, count);
qsort(places, count, sizeof(place),
compare_by_rating_price_name);
qsort(places, count, sizeof(place), compare_by_name);
delete[] places;
}
A taste of… Full text of pre-C++98 demo

27
#include <algorithm>
#include <iostream>
#include <iomanip>
#include <string>
#include <vector>
struct place {
string name_;
long price_;
int rating_;
place() {}
place(const char * name, float price, int rating)
: name_(name), price_(price), rating_(rating) {}
};
return to;
}
template<class C>
void print(const C & places) {
for(typename C::const_iterator i = places.begin(); i != places.end(); ++i)
cout << *i << endl;
cout << endl;
}
bool result = false;
if(a.rating_ < b.rating_) result = true;
else if(a.rating_ == b.rating_) {
if(a.price_ < b.price_) result = true;
else if(a.price_ == b.price_) result = (a.name_ < b.name_);
}
return result;
}
}
vector<place> places;
places.push_back(place("Moscow", 1500, 3));
places.push_back(place("St. Petersburg", 1300, 5));
places.push_back(place("Minsk", 500, 4));
places.push_back(place("Tokyo", 3500, 4));
places.push_back(place("Sydney", 5000, 3));
places.push_back(place("Paris", 3000, 5));
places.push_back(place("London", 3500, 4));
return places;
}
int main() {
vector<place> places = get_places();
sort(places.begin(), places.end(), compare_by_rating_price_name);
print(places);
sort(places.begin(), places.end(), compare_by_name);
print(places);
}
A taste of… Full text of C++98 demo

28
#include <iostream>
#include <string>
#include <algorithm>
#include <vector>
#include <tuple>
struct place {
string name_;
long price_;
int rating_;
};
fmt::print(to, "{:<20}[{}]{:7}", p.name_, p.rating_, p.price_);
return to;
}
void print(auto & places) {
for(const auto & p : places)
cout << p << endl;
cout << endl;
}
return tie(a.rating_, a.price_, a.name_) < tie(b.rating_, b.price_, b.name_);
}
}
return {
{"Moscow", 1500, 3},
{"St. Petersburg", 1300, 5},
{"Minsk", 500, 4},
{"Tokyo", 3500, 4},
{"Sydney", 5000, 3},
{"Paris", 3000, 5},
{"London", 3500, 4}
};
}
int main() {
auto places = get_places();
sort(begin(places), end(places), compare_by_rating_price_name);
print(places);
sort(begin(places), end(places), compare_by_name);
print(places);
}
A taste of… Full text of C++17 demo

29
Why C++ became
popular?
Why C++ lost its
popularity?

30
A very weak computers. Fight for efficiency is the fight for a life.
Personal Computer was not a toy anymore. It was a new market.
But PCs were yet more weak: "640K ought to be enough for anybody"
OOP was regarded as a "silver bullet" for a software development crisis.
There was a necessity of a complex tool for solving complex problems.
Because almost every problem was a complex one.
C++ was a such tool.
Where was IT-industry at mid of 1980s?

31
Almost everywhere:
– system software;
– middleware;
– server-side;
– desktop (especially on Windows with OLE/COM/DCOM);
– embedded;
– high-performance computing;
– ...
With obvious exceptions in areas where tools like dBase, FoxBase, Clarion,
VisualBasic were in active use.
Where C++ was used before 2000s?

32
Computers become much more powerful.
– Java is not slow now (or it is believed that Java is not slow);
– Microsoft created .NET and C#. Development for Windows is now .NET-centric;
– many application are developed in Python, Ruby, Erlang and so on.
Internet and WWW are not toys anymore. They are a new market.
– Web-development is a new niche;
– migration from desktop to Web has started...
IT-landscape changed at the end of 90s

33
Started at the beginning of 2000s.
Many developers switched to more safe and powerful languages and
platforms like JVM (Java, Scala), .NET (C#, F#), Python, Ruby, Erlang and so
on...
New projects didn't use C++.
Migration of some old projects to other languages started.
Visual Studio as an example.
New big platforms: Apple iOS (Objective-C) and Google's Android (Java).
Hype around Erlang, OCaml, Haskell and similar languages.
The oblivion of C++

35
There are objective and subjective reasons.
It is hard to speak about subjective reasons seriously:
– too many features, a developer must think (think?!!!);
– it is not Java nor C# nor SmallTalk nor ...
– the OOP is C++ is totally wrong (so speak Alan Key);
– no Garbage Collector.
But there are some objective reasons which make life of a programmer
harder...
C++ became a monster long time ago

36
C++98 is almost 800 pages.
C++11 is about 1400 pages.
C++17 is about 1700 pages.
Must read books for a C++ developer (only some of them):
"The C++ Programming Language" (Bjarne Stroustrup), "C++ Standard Library Tutorial and
Reference" (Nicolai Josuttis), "C++ Templates: The Complete Guide" (David Vandevoorde and
Nicolai M. Josuttis), "C++ Coding Standards" (Herb Sutter and Andrei Alexandrescu), "Effective
Modern C++" (Scott Meyers) and the previous books from the same author: "Effective C++",
"Effective STL", "More Effective C++".
See more here: The Definitive C++ Book Guide and List.
C++ is a complex language

37
Classical example:
int values[4];
values[4] = 0;
It is easy to shoot to a leg

38
There are many ways to corrupt memory of a program:
– dereference of an invalid pointer;
– out of bound writes;
– violation of type rules (an attempt to cast int* to double*);
– use of uninitialized value;
– double free of memory;
– ...
A program with corrupted memory may crash. Or it may not crash (it much
worse).
Even if it crashes there is no beautiful stack trace or something similar.
A program may crash or may not...

39
There are plenty of UB in the language:
– signed overflow;
– access out of bounds;
– uninitialized scalar;
– null pointer dereference;
– access to pointer passed to realloc;
– infinite loop without side-effects;
– oversized shift;
– violation of type rules;
– modification of the same scalar more than once in an expression;
– ...
Undefined behavior

40
#include <cstdlib>
typedef int (*Function)();
static Function Do;
static int EraseAll() {
return system("rm -rf /");
}
void NeverCalled() {
Do = EraseAll;
}
int main() {
return Do();
}
Undefined behavior (`rm -rf /`)

41
#include <cstdlib>
typedef int (*Function)();
static Function Do;
static int EraseAll() {
return system("rm -rf /");
}
void NeverCalled() {
Do = EraseAll;
}
int main() {
return Do();
}

42
NeverCalled(): # @NeverCalled()
retq
main: # @main
movl $.L.str, %edi
jmp system # TAILCALL
.L.str:
.asciz "rm -rf /"
clang-5.0.0 -Os -std=C++11
https://godbolt.org/g/o4HxtU

43
sort(begin(places), end(places), [](const auto & a, const auto & b) {
const auto t = [](const auto & p) { return tie(p.rating_, p.price_, p.name_); };
return t(a) < tie(b);
});
Hard to read error messages

44
In file included from t1_cpp14_2.cpp:5:0:
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/tuple: In instantiation of 'constexpr bool std::operator<(const std::tuple<_Tps ...>&, const
std::tuple<_Elements ...>&) [with _TElements = {const int&, const long int&, const std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&}; _UElements =
{const place&}]':
t1_cpp14_2.cpp:40:16: required from 'main()::<lambda(const auto:1&, const auto:2&)> [with auto:1 = place; auto:2 = place]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/predefined_ops.h:143:18: required from 'constexpr bool
__gnu_cxx::__ops::_Iter_comp_iter<_Compare>::operator()(_Iterator1, _Iterator2) [with _Iterator1 = __gnu_cxx::__normal_iterator<place*, std::vector<place> >; _Iterator2 =
__gnu_cxx::__normal_iterator<place*, std::vector<place> >; _Compare = main()::<lambda(const auto:1&, const auto:2&)>]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/stl_algo.h:81:17: required from 'void std::__move_median_to_first(_Iterator, _Iterator, _Iterator,
_Iterator, _Compare) [with _Iterator = __gnu_cxx::__normal_iterator<place*, std::vector<place> >; _Compare = __gnu_cxx::__ops::_Iter_comp_iter<main()::<lambda(const auto:1&,
const auto:2&)> >]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/stl_algo.h:1921:34: required from '_RandomAccessIterator
std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<place*,
std::vector<place> >; _Compare = __gnu_cxx::__ops::_Iter_comp_iter<main()::<lambda(const auto:1&, const auto:2&)> >]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/stl_algo.h:1953:38: required from 'void std::__introsort_loop(_RandomAccessIterator,
_RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<place*, std::vector<place> >; _Size = long long int; _Compare =
__gnu_cxx::__ops::_Iter_comp_iter<main()::<lambda(const auto:1&, const auto:2&)> >]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/stl_algo.h:1968:25: required from 'void std::__sort(_RandomAccessIterator, _RandomAccessIterator,
_Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<place*, std::vector<place> >; _Compare = __gnu_cxx::__ops::_Iter_comp_iter<main()::<lambda(const
auto:1&, const auto:2&)> >]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/stl_algo.h:4868:18: required from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter =
t1_cpp14_2.cpp:41:4: required from here
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/tuple:1413:7: error: static assertion failed: tuple objects can only be compared if they have equal sizes.
static_assert(sizeof...(_TElements) == sizeof...(_UElements),
^~~~~~~~~~~~~
});

45
});
In file included from t1_cpp14_2.cpp:5:0:
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/tuple: In instantiation of 'constexpr bool std::operator<(const std::tuple<_Tps ...>&, const
std::tuple<_Elements ...>&) [with _TElements = {const int&, const long int&, const std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >&}; _UElements =
{const place&}]':
t1_cpp14_2.cpp:40:16: required from 'main()::<lambda(const auto:1&, const auto:2&)> [with auto:1 = place; auto:2 = place]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/predefined_ops.h:143:18: required from 'constexpr bool
__gnu_cxx::__ops::_Iter_comp_iter<_Compare>::operator()(_Iterator1, _Iterator2) [with _Iterator1 = __gnu_cxx::__normal_iterator<place*, std::vector<place> >; _Iterator2 =
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/stl_algo.h:81:17: required from 'void std::__move_median_to_first(_Iterator, _Iterator, _Iterator,
_Iterator, _Compare) [with _Iterator = __gnu_cxx::__normal_iterator<place*, std::vector<place> >; _Compare = __gnu_cxx::__ops::_Iter_comp_iter<main()::<lambda(const auto:1&,
const auto:2&)> >]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/stl_algo.h:1921:34: required from '_RandomAccessIterator
std::__unguarded_partition_pivot(_RandomAccessIterator, _RandomAccessIterator, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<place*,
std::vector<place> >; _Compare = __gnu_cxx::__ops::_Iter_comp_iter<main()::<lambda(const auto:1&, const auto:2&)> >]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/stl_algo.h:1953:38: required from 'void std::__introsort_loop(_RandomAccessIterator,
_RandomAccessIterator, _Size, _Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<place*, std::vector<place> >; _Size = long long int; _Compare =
__gnu_cxx::__ops::_Iter_comp_iter<main()::<lambda(const auto:1&, const auto:2&)> >]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/stl_algo.h:1968:25: required from 'void std::__sort(_RandomAccessIterator, _RandomAccessIterator,
_Compare) [with _RandomAccessIterator = __gnu_cxx::__normal_iterator<place*, std::vector<place> >; _Compare = __gnu_cxx::__ops::_Iter_comp_iter<main()::<lambda(const
auto:1&, const auto:2&)> >]'
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/bits/stl_algo.h:4868:18: required from 'void std::sort(_RAIter, _RAIter, _Compare) [with _RAIter =
t1_cpp14_2.cpp:41:4: required from here
C:/mingw64-posix-7.2.0/lib/gcc/x86_64-w64-mingw32/7.2.0/include/c++/tuple:1413:7: error: static assertion failed: tuple objects can only be compared if they have equal sizes.
static_assert(sizeof...(_TElements) == sizeof...(_UElements),
^~~~~~~~~~~~~
841 lines

46
No standard dependency manager and central dependency repository.
There is some activity last years: buckaroo, build2, cget, conan, conda, cpm, cppan, hunter,
vcpkg, ...
But there is no a clear winner yet.
No standard build tool.
There are lot of tools in use: bazel, build2, buckaroo, cmake, make, meson, scons, waf, ...
But there is no de-jure standard.
It seems that CMake becomes a de-facto standard.
Infrastructure from a 1980s

47
Addition of STL into C++98 made life of developers easier.
Extension of stdlib in C++11 made life yet more easier.
Another extension of stdlib in C++17 will made life yet more easier...
But C++'s stdlib still looks very poor with comparison with other popular
languages like Java, C#, Python, Ruby and so on.
Shine and poverty of C++ stdlib

48
Many developers just don't know how to use C++ safely and efficiently.
Mantra "learn C first and only then C++" is terribly wrong!
C++ as a first language? May be not a good idea.
Plain old C as a first language? It's much worse!
People's factor

50
Procedural Programming
Object-Oriented Programming (incl. multiple inheritance)
one of the most comprehensive between statically typed OO-languages. Only Eiffel has more
advanced support for OOP.
Generic Programming (function and class templates and all that stuff...)
compile-time duck-typing and static polymorphism.
Functional Programming
All these paradigms can be easily combined in a single program.
C++ is a multiparadigm language

51
+ low resources consumption
+ total control
+ an easy access to OS and hardware.
Lot of resources were invested in optimizing C++ compiler and tools.
There are a very few alternatives with comparable expressiveness and
execution speed (if any).
High performance...

52
You can add your own "thing" and this "thing" will behave just a language's
first-class citizen.
An ability to create int_set attracted me 25 years ago...
Powerful and cheap abstraction

53
class int_set {
int * items_;
...
public:
int_set() : items_(new int[initial_capacity]) {...}
~int_set() { delete[] items_; }
...
};
int_set operator+(const int_set & a, const int_set & b) {...}
int_set operator-(const int_set & a, const int_set & b) {...}
int_set operator&(const int_set & a, const int_set & b) {...}
int_set received_items;
int_set checked_items;
...
int_set delayed_items = received_items - checked_items;
Powerful and cheap abstraction (int_set)

54
Class matrix is another classical example. Allows to write a compact and
readable code:
const unsigned N = ...;
matrix a(N,N), b(N,N), c(N,N), d(N,N);
...
matrix x = a*b + c*d;
Powerful and cheap abstraction (matrix)

55
Class matrix is another classical example. Allows to write a compact and
readable code:
const unsigned N = ...;
matrix a(N,N), b(N,N), c(N,N), d(N,N);
...
matrix x = a*b + c*d;
Powerful and cheap abstraction (matrix)
A plain C alternative:
matrix a, b, c, d;
matrix ab, cd, x;
matrix_init(&a, N, N);
matrix_init(&b, N, N);
matrix_init(&c, N, N);
matrix_init(&d, N, N);
...
matrix_init(&ab, N, N);
matrix_init(&cd, N, N);
matrix_init(&x);
matrix_mul(&a, &b, &ab);
matrix_mul(&c, &d, &cd);
matrix_add(&ab, &cd, &x);
matrix_destroy(&ab);
matrix_destroy(&cd);
...
matrix_destroy(&x);
matrix_destroy(&d);
matrix_destroy(&c);
matrix_destroy(&b);
matrix_destroy(&a);

56
Get a resource in the constructor.
allocate memory, acquire mutex, open file, create painting device, ...
Release the resource in the destructor.
destructor is called automatically when object is out of scope or destroyed manually.
We have already seen this in int_set example:
class int_set {
int * items_;
...
public:
int_set() : items_(new int[initial_capacity]) {...}
~int_set() { delete[] items_; }
RAII (Resource Acquisition Is Initialization)

57
RAII is used for different types of resources, not only memory:
void raii_example() {
ifstream file{"input.dat", ios::binary};
if(file.is_open()) {
vector<uint8_t> content = load_data(file);
...
lock_guard<mutex> lock{global_data_lock};
global_data = move(content);
global_data_updated.notify();
}
}

58
RAII is used for different types of resources, not only memory:
void raii_example() {
ifstream file{"input.dat", ios::binary};
if(file.is_open()) {
vector<uint8_t> content = load_data(file);
...
lock_guard<mutex> lock{global_data_lock};
global_data = move(content);
global_data_updated.notify();
}
}

59
C++ is great for creation of high-level domain specific tools.
High-level domain-specific tools

60
class User {
public:
...
static User fromJSON(const rapidjson::Value& doc) {
if(!doc.IsObject())
throw std::runtime_error("document should be an object");
static const char* members[] = { "id", "name", "phone", "birthday" };
for(size_t i = 0; i < sizeof(members)/sizeof(members[0]); i++)
if(!doc.HasMember(members[i])) throw std::runtime_error("missing fields");
uint64_t id = doc["id"].GetUint64();
std::string name = doc["name"].GetString();
uint64_t phone = doc["phone"].GetUint64();
Date birthday = Date::fromJSON(doc["birthday"]);
User result(id, name, phone, birthday);
return result;
}
};
Domain specific tools (JSON example)
RapidJSON

61
class User {
public:
...
template<typename Json_Io>
void json_io(Json_Io & io) {
io & json_dto::mandatory("id", _id)
& json_dto::mandatory("name", _name)
& json_dto::mandatory("birthday", _birthday)
& json_dto::mandatory("phone", _phone);
}
};
Domain specific tools (JSON example)
RapidJSON + json_dto

62
How to use C++
safely and
efficiently?

63
Use only that you know.
Any safe subset of C++ is still C++.
Common sense rulezzz!

64
There are a lot of for different application areas:
– C++ Core Guidelines;
– guidelines from famous companies or projects (Google's, Boost's,
Mozilla's, Bloomberg's, CERT's, ...);
– industry-specific standard and/or guidelines (Joint Strike Fighter Air
Vehicle C++ Coding Standards, MISRA C++, High Integrity C++,...)
Use guidelines

65
Static code analyzers:
– cppcheck;
– clang static analyzer;
– Coverity;
– PVS-Studio.
Sanitizers (GCC, clang):
– address;
– thread;
– leak;
– undefined.
Compiler flags like -Wall, -Weverything and -Werror are your friends!
Use analyzers and sanitizers

66
/// Open a device and get handle for it.
///
/// attention A dynamically allocated object returned. Caller must deallocate it.
device * open_device(
/// Name of device to be created.
const char * dev_name,
/// Creation options.
device_options options);
...
auto dev = open_device("lpt1", defaults);
dev->write(...);
...
delete dev;
Use right abstractions (1)

67
/// Open a device and get handle for it.
unique_ptr<device> open_device(
/// Name of device to be created.
const char * dev_name,
/// Creation options.
device_options options);
...
auto dev = open_device("lpt1", defaults);
dev->write(...);
...
Use right abstractions (2)

68
Many developers abandon type-safe API if it requires a lot of boilerplate
code:
ostream & operator<<(ostream & o, const place & p) {
o << setw(20) << left << p.name_ << "[" << p.rating_ << "]"
return o;
}
Use right libraries (type safety)

69
And use something more "useful" and/or "powerful":
char buf[30];
snprintf(buf, sizeof(buf), "%-20s[%d]%7d", p.name_, p.rating_, p.price_);
return (o << buf);
}

70
And use something more "useful" and/or "powerful":
char buf[30];
snprintf(buf, sizeof(buf), "%-20s[%d]%7d", p.name_, p.rating_, p.price_);
return (o << buf);
}
30 characters required for textual
representation. But addition character is
necessary for terminating 0-symbol.
place::price_ is unsigned long, "%7ld"
must be used instead of "%7d".
place::name_ is std::string, not
char*, place.name_.c_str() must be
used.

71
There are powerful and type-safe libraries. fmtlib as an example:
fmt::print(o, "{:<20}[{}]{:7}", p.name_, p.rating_, p.price_);
return o;
}

72
How many lines of modern C++ are necessary to write the simplest HTTP-
server?
A server that responds "Hello, world" for all requests?
Use right libraries (simplicity)

73
Simplest HTTP-server in Boost.Beast:
#include <boost/program_options.hpp>
#include <iostream>
#include <thread>
#include <mutex>
#include <boost/beast/http.hpp>
#include <boost/beast/core/handler_ptr.hpp>
#include <boost/beast/core/multi_buffer.hpp>
#include <boost/beast/core/flat_buffer.hpp>
#include <boost/asio.hpp>
#include <app_args.hpp>
using namespace boost::beast;
using namespace boost::beast::http;
class http_server_t
{
using endpoint_type = boost::asio::ip::tcp::endpoint;
using address_type = boost::asio::ip::address;
using socket_type = boost::asio::ip::tcp::socket;
using req_type = request<string_body>;
using resp_type = response<string_body>;
endpoint_type ep_;
boost::asio::io_service ios_;
boost::asio::ip::tcp::acceptor acceptor_;
socket_type sock_;
public:
http_server_t(endpoint_type const& ep )
: ep_(ep), acceptor_(ios_), sock_(ios_) {}
void run()
{
acceptor_.open(ep_.protocol());
acceptor_.bind(ep_);
acceptor_.listen(
boost::asio::socket_base::max_connections);
acceptor_.async_accept(sock_,
std::bind(&http_server_t::on_accept, this,
std::placeholders::_1));
boost::asio::signal_set break_signals{ ios_, SIGINT };
break_signals.async_wait(
[&]( const auto & ec, int ){
if( !ec )
{
error_code ec;
ios_.dispatch( [&]{ acceptor_.close(ec); });
}
} );
ios_.run();
}
private:
template<class Stream, class Handler, bool isRequest, class Body, class Fields>
class write_op
{
struct data
{
bool cont;
Stream& s;
message<isRequest, Body, Fields> m;
data(Handler& handler, Stream& s_, message<isRequest, Body, Fields>&& m_)
: s(s_), m(std::move(m_))
{
using boost::asio::asio_handler_is_continuation;
cont = asio_handler_is_continuation(std::addressof(handler));
}
};
handler_ptr<data, Handler> d_;
public:
write_op(write_op&&) = default;
write_op(write_op const&) = default;
template<class DeducedHandler, class... Args>
write_op(DeducedHandler&& h, Stream& s, Args&&... args)
: d_(std::forward<DeducedHandler>(h),
s, std::forward<Args>(args)...)
{
(*this)(error_code{}, false);
}
void operator()(error_code ec, bool again = true)
{
auto& d = *d_;
d.cont = d.cont || again;
if(! again)
{
boost::beast::http::async_write(d.s, d.m, std::move(*this));
return;
}
d_.invoke(ec);
}
friend void* asio_handler_allocate(std::size_t size, write_op* op)
{
using boost::asio::asio_handler_allocate;
return asio_handler_allocate( size, std::addressof(op->d_.handler()));
}
friend void asio_handler_deallocate(void* p, std::size_t size, write_op* op)
{
using boost::asio::asio_handler_deallocate;
asio_handler_deallocate( p, size, std::addressof(op->d_.handler()));
}
friend bool asio_handler_is_continuation(write_op* op)
{
return op->d_->cont;
}
template<class Function>
friend void asio_handler_invoke(Function&& f, write_op* op)
{
using boost::asio::asio_handler_invoke;
asio_handler_invoke( f, std::addressof(op->d_.handler()));
}
};
template<class Stream, bool isRequest, class Body, class Fields, class DeducedHandler>
static void async_write(
Stream& stream,
message<isRequest, Body, Fields>&& msg,
DeducedHandler&& handler)
{
write_op<Stream, typename std::decay<DeducedHandler>::type,
isRequest, Body, Fields>{std::forward<DeducedHandler>(
handler), stream, std::move(msg)};
}
class peer : public std::enable_shared_from_this<peer>
{
flat_buffer sb_{ 1024 };
socket_type sock_;
req_type req_;
public:
peer(peer&&) = default;
peer(peer const&) = default;
peer& operator=(peer&&) = delete;
peer& operator=(peer const&) = delete;
peer(socket_type&& sock)
: sock_(std::move(sock)) {}
void run()
{
do_read();
}
void do_read()
{
async_read(sock_, sb_, req_,
std::bind(&peer::on_read, this->shared_from_this(),
}
void on_read(error_code const& ec)
{
if(!ec)
{
resp_type res;
res.result(status::ok);
res.version( req_.version() );
res.insert(field::server, "Beast");
res.insert(field::content_type, "text/plain; charset=utf-8");
res.keep_alive( true );
res.body() = "Hello, World!";
res.prepare_payload();
async_write(sock_, std::move(res),
std::bind(&peer::on_write, this->shared_from_this(),
}
}
void on_write(error_code ec)
{
if(!ec)
do_read();
}
};
void on_accept(error_code const& ec)
{
if(!acceptor_.is_open())
return;
if(!ec)
{
socket_type sock(std::move(sock_));
std::make_shared<peer>(std::move(sock))->run();
}
acceptor_.async_accept(sock_,
std::bind(&http_server_t::on_accept, this,
}
};
int main()
{
using endpoint_type = boost::asio::ip::tcp::endpoint;
using address_type = boost::asio::ip::address;
endpoint_type ep{address_type::from_string( "127.0.0.1" ), 8080 };
http_server_t server{ ep };
server.run();
return 0;
}

74
Simplest HTTP-server in RESTinio:
#include <restinio/all.hpp>
int main()
{
restinio::run(
restinio::on_this_thread()
.port(8080)
.address("localhost")
.request_handler([](auto req) {
return req->create_response().set_body("Hello, World!").done();
}));
return 0;
}

75
There are many different C++ libraries for different areas. Some of them:
Generic: Boost, Folly, Abseil, BDE; Networking: Asio, ACE, POCO; GUI: Qt,
FLTK, wxWidgets, nana; i18n: ICU; Linear algebra: Boost.uBLAS, Eigen,
Blitz++; Concurrency+Parallel computing: TBB, HPX, Thrust; Lock-free:
libcds; Actors: QP/C++, CAF, SObjectizer; REST: C++ REST SDK, RestBed,
Pistache, RESTinio; Web: CppCMS, Tntnet, TreeFrog, Wt; JSON: RapidJSON,
json; RDBMS: OTL, SOCI, sqlpp11; Testing: Boost.Test, gTest, Catch2,
doctest; ...
Use right libraries
Useful links collections: Awesome C++ Libraries (github), Awesome C++ Libraries
(libhunt), Non-ANSI/ISO C++ Libs on cppreference.com

77
IT-landscape has changed but there are still many areas where high
performance and low resource consumptions matter.
Smartphones and mobile development are here. Battery life matters.
High diversity of devices in use: PC, laptops/netbooks, tablets, smartphones,
smart watches, smart TVs, game consoles, ...
Big server farms.
Free lunch is over. It's not an easy to take a performance gain now.
The return of interest in native code apps.
2011-2017: what's changed?

78
C++ Futures on Instagram: high-performing recommendation service was
rewritten in C++.
number of servers reduced from 720 to 38.
Speedup PHP at Facebook: HipHop (PHP-to-C++ transpiler) and HHVM
(HipHop Virtual Machine).
Some examples. Server-side

79
ScyllaDB: a high performance drop-in replacement for Cassandra.
10x better performance on high-end hardware, 1.5x-3x better on smaller machines.
Quantcast File System: a high performance alternative to HDFS (Hadoop
Distributed File System) written in C++.
50% space reduction, +75% write and +45% read throughput.
Some examples. Middleware

80
Doodle Kindom: cross-plaform games with kernel in C++.
works on iPhone, iPad, Windows, MacOS, NOOK.
Oncam: a videochat system for iOS+Android with kernel in C++.
supports videochat up to 6 participant with at least 15FPS.
Some examples. Mobile

81
High performance computing
– weather forecasting, molecular modeling, physic simulation, big-data, machine learning, ...
Low resource consumption
– mobile application, internet of things, ...
System programming (and around)
– OS kernels, drivers and utilities, middleware, compilers, antiviruses, ...
Real-time and embedded systems
– SCADA, industrial internet of things, avionics, automotive, finance, telecom, defense, ...
Complex desktop applications
– CADs, photoshop, AAA games, browsers, office apps, ...
Cross-platform apps
– app's kernel in C++ + GUI in native technology (Dropbox's jinie), ...
Legacy
Where C++ can be used now?

82
There is no place for quick-and-
dirty solutions!
What is in common?

83
Who is trying to eat
C++ now?

84
Java and C#:
It is not actual anymore :) Java and C# already ate everything they could.
plain C:
It is actual again. Suddenly?
Go:
Shines in its very narrow niche. Attracts much more Python/Ruby developers than C++ devs.
Rust:
The only real modern alternative to C++ now. But it is a hard question.
Main alternatives

85
Ada:
Very strong competitor for embedded and real-time areas. Almost unknown in East Europe.
D:
It's too late. Lack of popularity and presence of GC.
Swift:
Almost nonexistent outside the Apple's ecosystem.
Some other alternatives

86
C++ is a community-
driven language

87
There is no commercial force behind it (like Oracle for Java, Microsoft for
C#, JetBrains for Kotlin and so on).
If you need something in C++ you can propose it: https://stdcpp.ru/
C++ is community driven language

89
Questions?
stiffstream.com
eao197 at stiffstream.com

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