I am somewhat dismayed that contracts were accepted. It feels like piling on ever more complexity to a language which has already surpassed its complexity budget, and given that the feature comes with its own set of footguns I'm not sure that it is justified.
Here's a quote from Bjarne,
> So go back about one year, and we could vote about it before it got into the standard, and some of us voted no. Now we have a much harder problem. This is part of the standard proposal. Do we vote against the standard because there is a feature we think is bad? Because I think this one is bad. And that is a much harder problem. People vote yes because they think: "Oh we are getting a lot of good things out of this.", and they are right. We are also getting a lot of complexity and a lot of bad things. And this proposal, in my opinion is bloated committee design and also incomplete.
I can’t speak to the C++ contract design — it’s possible bad choices were made. But contracts in general are absolutely exactly what C++ needs for the next step of its evolution. Programming languages used for correct-by-design software (Ada, C++, Rust) need to enable deep integration with proof assistants to allow showing arbitrary properties statically instead of via testing, and contracts are /the/ key part of that — see e.g. Ada Spark.
Right, I think the tension here is that we would like contracts to exist in the language, but the current design isn't what it needs to be, and once it's standardized, it's extremely hard to fix.
The people who did contracts are aware of ada/spark and some have experience using it. Only time will tell if it works in c++ but they at least did all they could to give it a chance.
Note that this is not the end of contrats. This is a minimun viable start that they intend to add to but the missing parts are more complex.
Might be the case that Ada folks successfully got a bad version of contracts not amenable for compile-time checking into C++, to undermine the competition. Time might tell.
C++ is the last language I'd add to any list of languages used for correct-by-design - it's underspecified in terms of semantics with huge areas of UB and IB. Given its vast complexity - at every level from the pre-processor to template meta-programming and concepts, I simply can't imagine any formal denotational definition of the language ever being developed. And without a formal semantics for the language, you cannot even start to think about proof of correctness.
This is awesome. I've was a dev on the C++ team at MS in the 90s and was sure that RTTI was the closest the language would ever get to having a true reflection system.
No, because most major compilers don't support header units, much less standard library header units from C++26.
What'll spur adoption is cmake adopting Clang's two-step compilation model that increases performance.
At that point every project will migrate overnight for the huge build time impact since it'll avoid redundant preprocessing. Right now, the loss of parallelism ruins adoption too much.
The best thing the C++ WG could do is to spend an entire release cycle working on modules and packaging.
It's nice to have new features, but what is really killing C++ is Cargo. I don't think a new generation of developers are going to be inspired to learn a language where you can't simply `cargo add` whatever you need and instead have to go through hell to use a dependency.
In my experience, no one does build systems right; Cargo included.
The standard was initially meant to standardize existing practice. There is no good existing practice. Very large institutions depending heavily on C++ systematically fail to manage the build properly despite large amounts of third party licenses and dedicated build teams.
With AI, how you build and integrate together fragmented code bases is even more important, but someone has yet to design a real industry-wide solution.
Agreed, arcane cmake configs and or bash build scripts are genuinely off-putting. Also cpp "equivalents" of cargo which afaik are conan and vcpkg are not default and required much more configuring in comparison with cargo. Atleast this was my experience few years ago.
It's fundamentally different; Rust entirely rejects the notion of a stable ABI, and simply builds everything from source.
C and C++ are usually stuck in that antiquated thinking that you should build a module, package it into some libraries, install/export the library binaries and associated assets, then import those in other projects. That makes everything slow, inefficient, and widely dangerous.
There are of course good ways of building C++, but those are the exception rather than the standard.
The idea is great, the execution is terrible. In JS, modules were instantly popular because they were easy to use, added a lot of benefit, and support in browsers and the ecoysystem was fairly good after a couple of years. In C++, support is still bad, 6 years after they were introduced.
No idea if modules themselves are failed or no, but if c++ wants to keep fighting for developer mindshare, it must make something resembling modules work and figure out package management.
yes you have CPM, vcpkg and conan, but those are not really standard and there is friction involved in getting it work.
Much like contracts--yes, C++ needs something modules-like, but the actual design as standardized is not usable.
Once big companies like Google started pulling out of the committee, they lost their connection to reality and now they're standardizing things that either can't be implemented or no one wants as specced.
Finally, reflection has arrived, five years after I last touched a line in c++. I wonder how long would it take the committee, if ever, to introduce destructing move.
Here's a quote from Bjarne,
> So go back about one year, and we could vote about it before it got into the standard, and some of us voted no. Now we have a much harder problem. This is part of the standard proposal. Do we vote against the standard because there is a feature we think is bad? Because I think this one is bad. And that is a much harder problem. People vote yes because they think: "Oh we are getting a lot of good things out of this.", and they are right. We are also getting a lot of complexity and a lot of bad things. And this proposal, in my opinion is bloated committee design and also incomplete.
Note that this is not the end of contrats. This is a minimun viable start that they intend to add to but the missing parts are more complex.
What'll spur adoption is cmake adopting Clang's two-step compilation model that increases performance.
At that point every project will migrate overnight for the huge build time impact since it'll avoid redundant preprocessing. Right now, the loss of parallelism ruins adoption too much.
It's nice to have new features, but what is really killing C++ is Cargo. I don't think a new generation of developers are going to be inspired to learn a language where you can't simply `cargo add` whatever you need and instead have to go through hell to use a dependency.
https://mesonbuild.com/
And Mesons awesome dependency handling:
https://mesonbuild.com/Dependencies.html
https://mesonbuild.com/Using-the-WrapDB.html#using-the-wrapd...
After reading about GNU Autotools (help!) and suffering ever awful thing Java created I wondered if C/C++ could do better. They do. For years :)
The standard was initially meant to standardize existing practice. There is no good existing practice. Very large institutions depending heavily on C++ systematically fail to manage the build properly despite large amounts of third party licenses and dedicated build teams.
With AI, how you build and integrate together fragmented code bases is even more important, but someone has yet to design a real industry-wide solution.
C and C++ are usually stuck in that antiquated thinking that you should build a module, package it into some libraries, install/export the library binaries and associated assets, then import those in other projects. That makes everything slow, inefficient, and widely dangerous.
There are of course good ways of building C++, but those are the exception rather than the standard.
What are the good ways?
yes you have CPM, vcpkg and conan, but those are not really standard and there is friction involved in getting it work.
Once big companies like Google started pulling out of the committee, they lost their connection to reality and now they're standardizing things that either can't be implemented or no one wants as specced.
Proper reflection is exciting.
Also, useful: https://gcc.gnu.org/projects/cxx-status.html