= C++

• http://yosefk.com/c++fqa/
• Arguments why is C not compatible with C++?
  • C allows sophisticated struct initialization like { .member[0] = "hello" }, C++ does not
  • The semantics of a void argument list: `fn()` means “variadic” in C and “no arguments“ in C++. `fn(void)` means “no arguments” in both

== G++ call

g++ -Wall -Wextra -Wnull-dereference -Wsuggest-attribute=const -flto -fanalyzer -Wfloat-equal -Wduplicated-branches -Wduplicated-cond -fsanitize=address -Wlogical-op -Wrestrict -Wuseless-cast -Wdouble-promotion -Wshadow -Wformat=2 -Wold-style-cast

“g++” == “gcc -xc++ -lstdc++ -shared-libgcc”

== Supported standards by GCC

       w/o GNU ext   w/ GNU ext
C++23  -std=c++2b  -std=gnu++2b
C++20  -std=c++20  -std=gnu++2b
C++17  -std=c++17  -std=gnu++17
C++14  -std=c++14  -std=gnu++14
C++11  -std=c++11  -std=gnu++11
C++98  -std=c++98  -std=gnu++98

== C uniform implementation

#ifdef __cplusplus 
extern "C" {
#endif
… declarations …
#ifdef __cplusplus 
}
#endif

== Constructor syntaxes

A a1 = A_factory_func();  // calls copy ctor
A a1(A_factory_func());   // calls copy ctor

A a1;                     // calls default ctor
a1 = A_factory_func();    // calls operator =

== Initialization syntax

A x(3);       // direct initialization (since C++98)
A x = A(3);   // copy initialization
                 (can be optimized into direct initialization if LHS and RHS have same type since C++17,
                  disabled with -fno-elide-constructors)

== curly brace syntax

https://stackoverflow.com/q/9976927

std::complex<double> c = {3,4};
auto e = std::complex<double>{3,4};

== best practice

via https://stackoverflow.com/a/9977536
  exact value provided             → assignment (=)
  stored-in-object values          → curly brace syntax
  else e.g. description of object  → parenthesis syntax

pitfall example:  string(50, 'x') vs. string{50, 'x'}

== SFINAE

"substitution failure is not an error"
1. try to replace the type argument with a real type and compile.
2. Fails? Then don't consider it as an error, but try to find overloaded functions such that it still compiles
Since C++03 more and more cases are not errors anymore but cases that can be caught
Seems to enable many patterns where compile-time checks about the provided type argument are done and it compiles iff it satisfies the conditions


== Grand C++ error explosion 2024

via https://tgceec.tumblr.com/post/74534916370/results-of-the-grand-c-error-explosion
• template<class T>class L{L<T*>operator->()};L<int>i=i->
• struct x struct z<x(x(x(x(x(x(x(x(x(x(x(x(x(x(x(x(x(y,x(y><y*,x(y*w>v<y*,w,x{}