constexpr exceptions are in!
November 23, 2024 at 11:30 AM
constexpr exceptions are in!
the beautiful thing about C++ reflection is no matter what you did wrong, clang will swear it's a constexpr problem
May 24, 2026 at 6:04 PM
the beautiful thing about C++ reflection is no matter what you did wrong, clang will swear it's a constexpr problem
A r e y o u r e a d y t o h a v e s o m e 『 f u n 』 ?
:3
:3
![A screenshot of a piece of Lua code being processed at compile-time in C++. Notably, it's also able to pull in data from a "requires" clause...!
```cpp
int main() {
constexpr auto original_file_span = std::embed<char>("zres/main.lua");
constexpr auto original_file = comptime_make_array<original_file_span.size(), true>(original_file_span);
constexpr big_buffer glob = recursive_parse("zres/main.lua");
std::printf("original file (\"%s\"):\n\n%s", "zres/main.lua", original_file.data());
std::printf("\n\n=================================================================================\n");
std::printf("`consteval recursive_parse` result:\n\n%s", glob.data());
return 0;
}
```
Output:
```sh
function main()
return 1 + base.value;
end
=================================================================================
`consteval recursive_parse` result:
-- base.lua
base = {
["value"] = 30
}
function main()
return 1 + base.value;
end
```](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:5bsnuwk6gpbbhjocl6fkzs3y/bafkreif56pfsir5fo4ds7hvwvbnfkoanelczo7owzvl7ila6qn6zbwhblu)
April 6, 2026 at 5:42 AM
A r e y o u r e a d y t o h a v e s o m e 『 f u n 』 ?
:3
:3
fear me and my wall of constexprs
May 6, 2025 at 2:36 AM
fear me and my wall of constexprs
constexpr exception types and constexpr containers (all of them*) are now in LWG on path to C++26
* with exception of std::hive because it is not in draft yet
* with exception of std::hive because it is not in draft yet
January 28, 2025 at 7:13 PM
constexpr exception types and constexpr containers (all of them*) are now in LWG on path to C++26
* with exception of std::hive because it is not in draft yet
* with exception of std::hive because it is not in draft yet
December 11, 2024 at 9:54 AM
"everybody" knows they shouldn't write
constexpr bool what = std::is_constant_evaluated();
nor use
if constexpr (std::constant_evaluated())
but do you know about
const bool wtf = std::is_constant_evaluated();
I'm really sorry 😶🌫️
constexpr bool what = std::is_constant_evaluated();
nor use
if constexpr (std::constant_evaluated())
but do you know about
const bool wtf = std::is_constant_evaluated();
I'm really sorry 😶🌫️
September 2, 2025 at 6:18 PM
"everybody" knows they shouldn't write
constexpr bool what = std::is_constant_evaluated();
nor use
if constexpr (std::constant_evaluated())
but do you know about
const bool wtf = std::is_constant_evaluated();
I'm really sorry 😶🌫️
constexpr bool what = std::is_constant_evaluated();
nor use
if constexpr (std::constant_evaluated())
but do you know about
const bool wtf = std::is_constant_evaluated();
I'm really sorry 😶🌫️
GCC got constexpr exceptions (in today's trunk):
compiler-explorer.com/z/PE58vqhYo
big kudos to Jakub Jelínek
compiler-explorer.com/z/PE58vqhYo
big kudos to Jakub Jelínek
Compiler Explorer - C++ (x86-64 gcc (trunk))
struct hana_exception: std::exception {
constexpr const char * what() const noexcept {
return "my custom error message";
}
};
constexpr bool test() {
throw hana_exception{};
};
c...
compiler-explorer.com
July 11, 2025 at 11:54 AM
GCC got constexpr exceptions (in today's trunk):
compiler-explorer.com/z/PE58vqhYo
big kudos to Jakub Jelínek
compiler-explorer.com/z/PE58vqhYo
big kudos to Jakub Jelínek
Modern C++ can be kinda pleasant actually?
Like constexpr, auto almost everywhere + brace initialization, user-defined literals, and concepts all help clean things up a bunch
Like constexpr, auto almost everywhere + brace initialization, user-defined literals, and concepts all help clean things up a bunch
November 29, 2025 at 5:15 PM
Modern C++ can be kinda pleasant actually?
Like constexpr, auto almost everywhere + brace initialization, user-defined literals, and concepts all help clean things up a bunch
Like constexpr, auto almost everywhere + brace initialization, user-defined literals, and concepts all help clean things up a bunch
constexpr <mutex>, <condition_variable>, <shared_mutex>, <random>
July 15, 2025 at 6:37 AM
constexpr <mutex>, <condition_variable>, <shared_mutex>, <random>
Sorry we dissappointed you. Not everything is constexpr :( Coroutines needs to wait for 29.
February 16, 2025 at 1:31 PM
Sorry we dissappointed you. Not everything is constexpr :( Coroutines needs to wait for 29.
(I am cruficied by the woke mob for not making this constexpr)
January 6, 2026 at 9:43 AM
(I am cruficied by the woke mob for not making this constexpr)
constexpr is my new best friend
March 23, 2025 at 8:40 AM
constexpr is my new best friend
`constexpr volatile`....save me...
`constexpr volatile`
save me `constexpr volatile`
`constexpr volatile`
save me `constexpr volatile`
January 16, 2025 at 5:28 PM
`constexpr volatile`....save me...
`constexpr volatile`
save me `constexpr volatile`
`constexpr volatile`
save me `constexpr volatile`
Guh. Finally fixed this up, and it tosses exceptions on failure now too.
![Command and console output:
cat ./main2.c++ && ./main2.c++.exe || echo return result value: $?
#include <embed>
#depend "MAINTAINERS"
int main () {
static constexpr std::span<const unsigned char> data =
std::embed<unsigned char>("MAINTAINERS", 0, 1);
static constexpr std::span<const std::byte> data2 =
std::embed<std::byte>("MAINTAINERS", 3, 1);
static constexpr std::span<const char> data3 =
std::embed<char>("MAINTAINERS", 6, 2);
static_assert(data.size() == 1);
static_assert(data[0] == 'N');
static_assert(data2.size() == 1);
static_assert((unsigned char)(data2[0]) == 'e');
static_assert(data3.size() == 2);
static_assert(data3[0] == '=');
static_assert(data3[1] == '=');
return (int)data2[0];
}
return result value: 101](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:5bsnuwk6gpbbhjocl6fkzs3y/bafkreicesfudwkwlvzrl2i63j6gdwvguqfy7fgjcnmwgj3n62d6zrjp6g4)
June 20, 2026 at 4:57 PM
Guh. Finally fixed this up, and it tosses exceptions on failure now too.
Meanwhile, reflection in C++26:
![template <typename T>
void Reflect(const T& t)
{
static constexpr T s{};
constexpr auto& [...x] = s;
auto& [...v] = t;
([&y=v]<auto p>(){std::println("{} = {}",[](std::string_view n){
n.remove_prefix(n.rfind("::")+2);n.remove_suffix(2);return n;}(
std::source_location::current().function_name()),y);}.template operator()<&x>(),...);
}](https://cdn.bsky.app/img/feed_thumbnail/plain/did:plc:mlabzvj2dn2ynqufgidmh2i4/bafkreifljj7sfrlxob2a4yuhl72wfjpkx7gcrv3enwzqudeilqk26ppmqe)
October 2, 2025 at 9:40 AM
Meanwhile, reflection in C++26:
🧮 C++23 + MSVC = compile-time math magic ✨
constexpr is arriving via LLVM libc in MSVC 14.52 Preview, enabling compile-time evaluation of math functions with improved accuracy and consistency. ⚙️🚀
Try /std:c++23 + /Zc:cmath and dive into the details!
📖 msft.it/63322aji2j
constexpr
Try /std:c++23 + /Zc:cmath and dive into the details!
📖 msft.it/63322aji2j
September 25, 2026 at 1:00 PM
🧮 C++23 + MSVC = compile-time math magic ✨
constexpr is arriving via LLVM libc in MSVC 14.52 Preview, enabling compile-time evaluation of math functions with improved accuracy and consistency. ⚙️🚀
Try /std:c++23 + /Zc:cmath and dive into the details!
📖 msft.it/63322aji2j
constexpr
Try /std:c++23 + /Zc:cmath and dive into the details!
📖 msft.it/63322aji2j
What I would like is "constexpr class", "constexpr namespace", or "constexpr module" that automatically adds "constexpr" to all content. I think that's a good compromise.
July 1, 2025 at 2:02 PM
What I would like is "constexpr class", "constexpr namespace", or "constexpr module" that automatically adds "constexpr" to all content. I think that's a good compromise.
c++26 has all containers (list, map, set, unordered_map, ...)* and most of standard exception types constexpr.
* with exception of std::hive (which also got just in)
* with exception of std::hive (which also got just in)
February 15, 2025 at 9:54 AM
c++26 has all containers (list, map, set, unordered_map, ...)* and most of standard exception types constexpr.
* with exception of std::hive (which also got just in)
* with exception of std::hive (which also got just in)
Also atomics in 26 are constexpr 🙈☺️🥰
December 4, 2025 at 8:15 PM
Also atomics in 26 are constexpr 🙈☺️🥰
-fimplicit-constexpr for clang (like already in GCC?) Sure! github.com/llvm/llvm-pr...
Any feedback appreciated!
Any feedback appreciated!
[clang] add `-fimplicit-constexpr` flag by hanickadot · Pull Request #136436 · llvm/llvm-project
Same as GCC's flag of the same name. If a function (constructor / destructor) doesn't have a constexpr nor consteval specifier. It will implicitly add constexpr.
This change doesn't tou...
github.com
April 19, 2025 at 3:31 PM
-fimplicit-constexpr for clang (like already in GCC?) Sure! github.com/llvm/llvm-pr...
Any feedback appreciated!
Any feedback appreciated!
Poking about with compile time consteval programming. Finally understanding why @hanicka.net wants everything to be constexpr. Also, trying to bridge the gap from compile time data to static constants at runtime is painful...
August 10, 2026 at 2:15 PM
Poking about with compile time consteval programming. Finally understanding why @hanicka.net wants everything to be constexpr. Also, trying to bridge the gap from compile time data to static constants at runtime is painful...