133
u/No-Adeptness5810 12h ago
Dude i migrated a massive project from c++17 to c++26 in like 15 minutes i dont get the drama
125
u/JVApen 9h ago
As someone responsible for these upgrades on a large project:
MSVC just announced they fully support C++23 in the . 52 compiler
It isn't just switching the version, it's also switching the compiler version
This comes with upgrade of related tooling (upgrade clang and clang-format and clang-tidy and clangd ...)
It also comes with upgrading the used OS (Ubuntu 22.04 -> 26.04)
Sometimes you see ICE (internal compiler error) popping up
Some breaking changes require work to resolve (like operator== in C++20)
Even if you no technical issues, you need to find the time while features have priority
You need material to 'teach' all employees
My experience: switching the version flag is the easy part
28
u/Juff-Ma 9h ago
Thank you, I've never had an internal compiler error and now will have nightmares about that for weeks.
9
u/itsTyrion 5h ago
i have. trying to compile software for a robot on outdated 32 bit Debian. because somehow that thing ran a 64 bit x86 CPU, but 32 bit userspace. I never got their shitty framework to compile
5
u/meneldal2 5h ago
It's pretty rare to get ICEs. Iirc stuff like early modules or concepts had some you could trigger somewhat easily but it was quickly fixed.
20
u/17HappyWombats 10h ago
We have a file logging library (zlog) with thousands of calls. We're not switching to std::format. Even after they fix it so it can do all the printf stuff. Just checking an LLM translation would break whoever got that job.
We're slowly moving to std::ranges::for_each/all_of/etc but that's not a migration so much as a progression when we change code that uses older versions.
There's a whole bunch of similar stuff, we mostly try to avoid having too much clang-tidy whining.
43
55
27
u/Luna_Wolfxvi 11h ago
Honestly some of the newer shit doesn't even look like C++ to me anymore. IE:
constexpr auto my_meta_type = int; // Reflected metadata of 'int' [:my_meta_type:] my_variable = 42; // Splicing it back into code; compiles as: int my_variable = 42;
33
u/fuj1n 11h ago
The code generation / reflection stuff is amazing.
Historically, when you'd need type information (without manually defining it), you'd have to add an extra compilation step where a custom tool either manually searches the codebase or interrogates a compiler API, now, you can just write compile-time code in your codebase that automagically populates a data structure for you with any type information you could desire.
It'll be really useful for my (hobby) game engine, where I was previously considering traversing the Clang AST
22
3
u/meneldal2 5h ago
If you look at what engines currently use for reflection (ugly macros mostly), this can be a huge improvement if the engine can be rewritten with this in mind.
But the sad part is I can only see maybe UE going with it with the next major release because they can force this kind of change, but open source stuff is never getting it most likely, way too much inertia.
7
u/17HappyWombats 10h ago
if(auto foo = call_some_function([parameters](const auto &thing){return test_the_thing(thing)}; foo == enum_type::operation_success) {there's code here;}That's perfectly valid and readable C++ and I won't hear otherwise.
(I am using std::optional a lot now that it kinda works. It's not a Rust Result but it's near enough for Australia)
8
u/Hohenheim_of_Shadow 6h ago
I love C++ because it's an un-opinionated, multi paradigm language where you can do whatever you want but that shit is horrendous. Freedom was a mistake.
I am glad you can code how you like, but corona virus social distancing protocols are in effect
3
u/17HappyWombats 6h ago
You get used to it, and if you expand the above back into C-style code it turns into an utter abomination. Especially with code where you need to write "if any of these, find a matching one of those" type sequences, and {hopefully soon... serialise it to JSON and send it}
Fundamentally C++ is limited by its roots, which is why Rust people are so unbearable {changes hats} about the utter perfection of the language.
2
u/Hohenheim_of_Shadow 3h ago
Hard disagree.
True C is readable, but kinda annoying it has to bring in pointers.Edit, realized I bungled the test_the_thing. Fuck it IDK, coding on mobile sucks
Int test_the_thing (*blah blah, args){ Return blah; } Void func(){ Blah result; If(test_the_thing(&result, args) ){ Do stuff; } }Cpp pass by reference makes it pretty sweet and simple for ez cases.
Int test_the_thing (&blah blah, args){ Return blah; } Void func(){ Blah result; If(test_the_thing(result, args) ){ Do stuff; } }The return result by argument pattern is a little eeeh, but it makes sense considering that's often how it has to work under the hood anyway. Optionals are syntactic sugar alternative for the same semantics.
Std::optional<blah> test_the_thing ( args){ Return args.blah; } Void func(){ Blah result=(test_the_thing( args); If(result ){ Do stuff; } }I can see why each incremental change is made and how it leads to what you like. E.g. yeah the two part of statement is kinda nice for this simple case. But the end result is pretty bad imo.
To me, it's like those overly clever nested ternary statements, but worse. Super fun to write, echnically a couple characters more concise, but so tangled together that reading it is miserable.
Defining and constructing an anonymous class in an if statements conditional is just way too much going on there for simple shit, and way way too much going on for complex shit!
But the beauty of c++ is that's just like my opinion sis and you can do you <3
4
-1
u/ValesQQ 10h ago
It seems valid but would the first “if”not always be true due to the single “=“ ?
8
u/Moist_Heat9523 9h ago
No, it’s an assignment, and this code tests the value that was assigned. So basically “foo = …; if (foo)”
2
u/17HappyWombats 8h ago
Yep, the shiny new if-two-statements, upgraded from the old if-statement. It's surprisingly convenient, partly because I used to get frustrated at not being able to explicitly test "if(auto foo=some_random_shit))" and I loathe implicit "nullptr is 0 and also false"
I eagerly std::await the even more improved if-three-statements-and-a-loop "operator" 🔥
1
u/SeriousPlankton2000 7h ago
Can't you do if ((auto foo = bar()) == baz) {barf()}; //?
2
u/17HappyWombats 6h ago edited 6h ago
Nope, that's not allowed. The previous standard let you say "
if(auto foo = something)" and if foo could be interpreted as a boolean you had a valid if() statement. The new one lets you have two statements, the auto assign and the test.The win here is the scoped auto variable, FWIW. If avoids the abominable pattern where you either alternate declaration/conditional, or a pile of declarations then a string of tests, mixing assignments in whatever way is least horrible. So you get a chain of declare-assign-test statements in a nice vertical line rather than a >
3
u/the_horse_gamer 7h ago
the compile time reflection is incredible. only zig and jai have something that can really match it in power, and they're significantly simpler languages.
33
u/Antervis 10h ago
C++03 -> 11 migration was a pain in the ass because of std::string changes, but after that it was basically just changing compiler flags, no?
18
u/Bemteb 10h ago
There are some minor things, if you are unlucky something might break going to 20. But it's mostly special cases, not something so big as string.
The main reason companies don't switch is "it's working, why invest time and money into switching?"
2
2
u/Antervis 10h ago
Depends on the companies. Tech giants would be losing potential employees if they stuck with outdated standards, and that loss outweighs costs of upgrades.
8
u/cpayne22 9h ago
Airlines and finance both employ a lot more than “tech giants”.
The real cost is the testing and compliance.
Any change needs to be documented and tested.
At the end of the day it’s a financial decision.
1
u/LutimoDancer3459 9h ago
Security updates, more and potentially better frameworks, more efficiency,... dont know about c++ but the things the java team added since 8... boy, the reduced server costs will pay for themselves pretty fast
3
u/17HappyWombats 10h ago
And turning on all the new warnings and hints and clang-tidy updates and cpp-check checks and other fun stuff. Wherein you learn that sometimes passing a std::string to printf "works" because of SSO, and it's worked in prod for ages.
1
u/meneldal2 5h ago
For Microsoft they dropped support for some stuff with newer versions. Which was outside of the standard so fair enough but can break projects.
Like references in unions.
1
u/ResponsibleWin1765 45m ago
I thought the entire reason why C++ is so convoluted is because it keeps everything around for backwards compatibility.
-1
u/megayippie 9h ago
The <=> operator was a big pain point. Many of our tests started failing with weird bugs
8
u/Antervis 9h ago
How? Pre-c++20 codebase won't even have them.
1
u/megayippie 9h ago
I honestly don't remember the details or the compiler version. I think the error was because some of our types only partly conformed to ideas of sorting, and that caused some weird interaction where some types in a vector didn't want to test for just ">=" but some other things as well, which we didn't need so didn't implement. Neither "==" nor ">" were there for our types.
The solution was to use more spaceship operators. The error message was clean but we didn't really know how <=> worked yet, so it delayed us a week or so.
3
u/Antervis 5h ago
Ehm... Standard algorithms and data structures use operator < though, even for equivalence.
2
u/SeriousPlankton2000 7h ago
If neither == nor > are there, how did your types end in a test that expects ordered-like behavior for your types?
2
-11
u/mas-mas-itu 12h ago
During 2012-2016, I was so excited and ambitious to learn and use C++ profesionally. Later on when its' standardization becoming more and more ridiculous, it does more damage to me rather on making things easier.
17
u/Anxious_Marsupial_59 12h ago edited 11h ago
C++ 20 (and the following streamlining of C++ 23) was a monumental upgrade in making it easier to use and avoiding foot guns without having to always write your own standard library, what are you even talking about?
33
u/Kinexity 12h ago
when its' standardization becoming more and more ridiculous
Literally all that was added over the years following C++11 are optional features. No one holds a gun to your head forcing you to use them.
-23
u/helanhalvan 12h ago
If those optional features where implementing sensible things, sure. For example, can you, using the standard library, print
vector<vector<int>>to stdout easily? As far as I can tell, no, you need to write loops or recursion yourself.16
u/tim_pipperton 12h ago
Is that really such a pressing issue? Regardless, reflection makes that way easier on the library side.
23
u/Kinexity 12h ago
Almost like as if there is no one single correct way to print out such structure. If you always want to print it out the same way then no one stops you from writing your own mini library to do it in your every project. Go back to Python if you want the language to hold your hand and decide stuff for you.
5
u/QuaternionsRoll 11h ago
Eh, debug printing is definitely an overlooked feature in C++. It’s possible that reflection will improve things somewhat, but hard to say
1
271
u/LoveOfSpreadsheets 12h ago
*cries in Java8*