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Myths & Sophisms

Old (> 40 years old)
No objects (cuz I think there is Java, Python, .Crap, and Blah Blah...)
No abstraction
C is a low-level system programming language and it sucks at writing every day apps (same people telling: “Let’s do it in node gurls”)
No dynamism
No sugar syntax (this one is kind of true if you don’t know the preprocessor)

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People’s fear : *POINTERS

Who fears pointers (and pointers of pointers of pointers)?

RAISE YOUR HANDS

Who just doesn’t get the point of it?

RAISE YOUR HANDS

Who ever had a nightmare of dereferencing a NULL and getting stabbed (literally) ?

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What’s C about anyways ?

Freedom, compiler won’t tell you what to do
Knowing what you do (pretty manual)
NO OBSCURE MAGIC AT THE END! (I look at you Javascript programmers)

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What’s a shared object?

Don’t think it’s an OO concept of objects plz…
Binary object (.o)
It is shared. (.so)
It is loadable.
Almost every programming language you like has its own system to load shared objects

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Compile-time linking

-l to the compiler you know
binds executable
needs library absolute path
Most common linking type
Either static (archive) or dynamic (shared objects)

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Overridable!!!

For shared objects

OS specific override loading of compile-time liked libraries
{LD_PRELOAD=... , DYLD_FORCE_FLAT_NAMESPACE=1 DYLD_INSERT_LIBRARIES=...}

THIS PARTICULAR POINT IS VERY IMPORTANT

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Runtime loading : dlload/dlsym

Loading it at runtime, not only at compile time
Not only with a “prototype”
This is how you do plugins

DEMOS

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UNIX API

What’s UNIX, I’m not kidding, some ppl think it’s Linux misspelled or something UNIX != Linux
What about POSIX and SUS?
The libc deals front-end (user-space-level) implementation
Kernel deals the back-end (system-calls) implementation
Let’s go deeper (Not a deep learning joke)

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I/O : file descriptors

open/close
read/write
dup/dup2

File descriptors are simple ints

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Pipes

What’s a pipe?
What’s the point

DEMO

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Sockets

Liking web?, of course
On UNIX, your userspace programs use them for every connection

DEMO

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C++ Part of the Presentation

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Runtime Abstraction

What’s runtime abstraction in C++ : virtual
Can we do it in C? Yes
How? Wait a second
Do we usually do it this way? depends

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How to deal in C

function pointers
int (*yass)(char *more_yasssss);
abstract structs of functions
fat pointers
etc.

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how the virtual keyword works

What’s a vtable?
how to use it

DEMO

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Abstraction

We talked earlier about runtime abstraction
What about compile-time abstraction?
Let’s show you what I mean

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Basic templating

Most of you are familiar with common templating
Particularly from the STL (Standard Template Library)

template <typename T>

class SomeClass {

T* data;

...

};

template <typename T>

void some_function(T &object) {

...

}

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Template specialization

Who knows them/ever used it? RAISE YOUR HANDS
What does it do?

template <typename T>

some_function(T &object) {� // code

}

template <>

some_fonction(size_t object) {

// other code

}

template <typename T>

class {

some_mtd();

};

template <>

class<size_t> {

some_other_mtd();

}

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The “Trait” Pattern

Very C++-specific
Some new programming languages, such as Rust (which I don’t like) use this pattern, built-in their type system
Very powerful
Provides high performance, highly optimizable generated code for compile time abstraction
DEMO

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The advantages of

C++11 templating

The “auto” keyword prevents a lot of problems at template-instantiation-time (much less public in-class typedefs to write)
Template-enabled “using” keyword

template <typename T> using vector_ptr = std::shared_ptr<std::vector<T> >;

Range-style for loops exploiting iterator-like objects cleanup the code style a lot.
And more.