The GCC C++ compiler (any many other C++ compilers as well) provide nonstandard extentions such as alloca() for stack based allocation variable length arrays, as they are part of the C standard C...

template <typename... Ts> struct A { template <typename C> constexpr auto proc() noexcept { return C{ }; } constexpr size_t size() noexcept { return sizeof...(Ts); } }; template &lt...

The CTRE library is able to parse and validate regular expressions at compile time using syntax like ctre::match<"REGEX">(text_to_search). I know this syntax is only supported...

I'm writing a constexpr code and I would like to inspect computed values at compile time. The usual trick is to do something like this: struct ReturnValue { int value1; int value2; }; constexpr...

Let's say I have a vector of a very simple struct: struct SimpleStruct { int a; int b; int c; }; std::vector<SimpleStruct> vs; I wish to sort this struct by 'a' leaving the positions of 'b' ...

Consider the following piece of code: struct B { friend bool operator< (const B&, const B&); friend bool operator==(const B&, const B&); }; struct D : B { friend std::strong_...

A handy method to verify if a positive integer n is a power of two (like 1, 2, 4, 8, etc.) is to use the following test for having no more than 1 bit set: bool test = n & (n - 1) == 0; This op...

The following code (godbolt): #include <iostream> #include <vector> #include <ranges> struct S { float x = 150.f; S f() const { return *this; } }; int main() { std::vect...

Consider this code: #include <iostream> #include <vector> #include <exception> void foo(std::exception const& e1) { try { std::cout << e1.what() << std::endl; ...

Anonymous enums are in common use for defining compile-time-only constants in a compiler-supported fashion (i.e. without resorting to Macros), in C. This is also true for C++ (because even while th...

I'm fairly new to C++ coroutines. When my app shuts down, I'd like to be able to give any outstanding co-routines a hint that I'd prefer they finished early. One solution/idea I came up with was to...

I was confused by the following paragraph about type aliasing from cppreference (source): Whenever an attempt is made to read or modify the stored value of an object of type DynamicType through a g...

In C++ Weekly - Ep 313 - The constexpr Problem That Took Me 5 Years To Fix!, Jason Turner demonstrates several compile-time techniques in order to construct a std::string at compile-time and then p...

Consider the following scenario: struct MyInterface {}; struct Data : MyInterface{}; struct DataWrapper { SomeContainerOf<MyInterface*> getData() {...} private: std::vector<Data...

The C++20 feature std::source_location is used to capture information about the context in which a function is called. When I try to use it with a variadic template function, I encountered a probl...

C++20 std::atomic has wait and notify_* member functions, but no wait_for/wait_until. The Microsoft STL implementation for std::atomic uses WaitOnAddress (when the OS is new enough to has it). And ...

The proposal for shared_ptr<T[N]> has this paragraph: https://www.open-std.org/JTC1/SC22/WG21/docs/papers/2014/n3920.html The unfortunate occurence of unique_ptr having lost its support for ...

I've got the following implementation of the c++ concept move_constructible from cppreference template<typename _Tp> concept move_constructible = constructible_from<_Tp, _Tp> &&amp...

I've reduced my code to the following example, which fails -O3 C++20 compilation on my g++ (x64 12.3) as well as apparently 14.1 when using godbolt: Again according to godbolt, clang works without ...

For some reason GCC regards variable a as an rvalue within the initialization of variable b (of which the expression is of type int&). And, as a result, rejects the code as it's not able to bin...

I'm dealing with the last big 4 of C++ 20, attempting to learn the new main features. Trying some code from the web related to ranges, I've written: std::vector ints{ 6, 5, 2, 8 }; auto even = [](i...

I want to loop through a vector in a sorted way without modifying the underlying vector. Can std::views and/or std::range be used for this purpose? I've successfully implemented filtering using vie...

The std::ranges::view concept in C++23 requires a view to be movable, which includes move-assignability. I understand why we want a view to be move-constructible, but why is the assignment necessar...

libc++ std::counting_semaphore uses atomic increment with memory_order_release in release method: void release(ptrdiff_t __update = 1) { if(0 < __a.fetch_add(__update, memory_order_release)) ...

I've encountered a really weird problem with clang. When I compile my code with C++20 using gcc-11 everything is fine. The problem appears when I try to compile it with C++20 and clang-14 (using cl...