classes, an illustrative example from a larger project • Project build issues • Inclusion of platform-specific header files • Concept hierarchies • Class and Function DesignOCP: The Open–Closed Principle header file to define the common definitions • The header file is responsible for including the platform-specific code • A series of preprocessor macros handles generating the header file name to load • result = vcopyq_laneq_f32(negation, 0, value, 0); return Quat(result); }Usage of Platform-specific Implementation Quat eval(Quat a, Quat b, Quat c) { return (a *

std::async(std::launch::async,...) Platform-specific APIsSpawning new threads There are lots of ways to spawn new threads: std::thread std::jthread std::async(std::launch::async,...) Platform-specific APIs They all have

EXPORT_UNDNAME #else #define EXPORT_UNDNAME __attribute__((visibility("default"))) #endif Platform-specific tricks to export a variable without mangling83 CppCon 2021 | auto load = [] { return plugi

Customizable Functions: ● Customization through policy-aware schedulers. ● Flexibility to support platform-specific optimizations. Example Customization: ● Using CUDA-specific scheduler for std::for_each.

3Why does C++ care about it? Standard C++03 didn’t have “threads.” You’d just use some platform-specific library, such as pthreads. But then what could the Standard say about multithreaded programs

Steagall K E W B C O M P U T I N G What is an ABI? • ABI (application binary interface) is the platform-specific specification of how entities defined in one TU interact with entities defined in another TU

trigger (ctrl_c.event()) completes… (demo 4)118 All that remains is a boat-load of nasty platform-specific hackery (hook Windows events, play clicky sounds). You can find all the demo code including

1 2 3 66.1Library - Utilities 67P1759 Native handles and file streams // No need to use platform-specific APIs to open the file { std::ofstream of("~/foo.txt"); auto lm = last_modified(of.native_handle());

spinning - rather than processing Not likely to get lock either - it is 1 of 19 waiting Speaker notes◼ : Ordinary Job ◼ : Processing Job ◼ : Saving Job (Waiting) ◼ : Saving Job (Writing) ◼ : CPU Usage regular jobs use 50% CPU 100% usage is SpinLocks - Followed by 20% usage in saving jobs Speaker notes38Speaker notesAVOID BLOCKING – CONFIRMATION • Changed from SpinLock to mutex • Result: ▪ CPU usage minimal Speaker notes◼ : Ordinary Job ◼ : Processing Job ◼ : Saving Job (Waiting) ◼ : Saving Job (Writing) ◼ : CPU Usage 40Same as before - except 100% usage replaced by 0% Speaker notes41Speaker notesAVOID

Functions can have zero or more inputs. This function has exactly one parameter of type std::string Notes on function parameters: ● Functions names must start with a letter or underscore. ● Note: Sometimes value returned. Functions return at most 1 value (The type is ‘void’ if we return no values). Notes on return values: ● There are a few ways to get more than 1 value returned from a function: ○ We the function name. Local variables declared in the function body follow normal scoping rules. Notes on function body: ● Later on we’ll see that the function body usually is defined in a source (.cpp)