Contracts feel like the right direction but the wrong execution timeline. The Ada/SPARK model shows how powerful contracts become when they feed into static verification — but that took decades of iteration on a language with far cleaner semantics. Bolting that onto C++ where UB is load-bearing infrastructure is a different beast entirely.
The real risk isn't complexity for complexity's sake — it's that a "minimum viable" contracts spec gets locked in, and then the things that would actually make it useful for proof assistants become impossible to retrofit because they'd break the v1 semantics. Bjarne's concern about "incomplete" is more worrying to me than "bloated."
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.
C++ contracts standardizes what people already do in C++. Where is the complexity in that? It removes the need to write your own implementation because the language provides a standard interoperable one.
An argument can be made that C++26 features like reflection add complexity but I don't follow that argument for contracts.
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.
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.
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.
The devil is in the details, because standardization work is all about details.
From my outside vantage point, there seems to be a few different camps about what is desired for contracts to even be. The conflict between those groups is why this feature has been contentious for... a decade now?
Some of the pushback against this form of contracts is from people who desire contracts, but don't think that this design is the one that they want.
Without a significant amount of needed context that quote just sounds like some awkward rambling.
Also almost every feature added to C++ adds a great deal of complexity, everything from modules, concepts, ranges, coroutines... I mean it's been 6 years since these have been standardized and all the main compilers still have major issues in terms of bugs and quality of implementation issues.
I can hardly think of any major feature added to the language that didn't introduce a great deal of footguns, unintended consequences, significant compilation performance issues... to single out contracts is unusual to say the least.
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.
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.
To me, the most important feature of Cargo isn't even the dependency management but that I don't ever need to tell it which files to compile or where to find them. The fact that it knows to look for lib.rs or main.rs in src and then recursively find all my other modules without me needing to specify targets or anything like that is a killer feature on its own IMO. Over the past couple of years I've tried to clone and build a number of dotnet packages for various things, but for an ecosystem that's supposedly cross-platform, almost none of them seem to just work by default when I run `dotnet build` and instead require at least some fixes in the various project files. I don't think I've ever had an issue with a Rust project, and it's hard not to feel like a big part of that is because there's not really much configuration to be done. The list of dependencies is just about the only thing in there that effects the default build; if there's any other configuration other than that and the basic metadata like the name, the repo link, the license, etc., it almost always will end up being specifically for alternate builds (like extra options for release builds, alternate features that can be compiled in, etc.).
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.
Speedy convenience beats absolute correctness anyday. Humans are not immortal and have finite amount of time for life and work. If convenience didn't matter, we would all still be coding in assembly or toggling hardware switches.
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.
It's not true that Rust rejects "the notion of a stable ABI". Rust rejects the C++ solution of freeze everything and hope because it's a disaster, it's less stable than some customers hoped and yet it's frozen in practice so it disappoints others. Rust says an ABI should be a promise by a developer, the way its existing C ABI is, that you can explicitly make or not make.
Rust is interested in having a properly thought out ABI that's nicer than the C ABI which it supports today. It'd be nice to have say, ABI for slices for example. But "freeze everything and hope" isn't that, it means every user of your language into the unforeseeable future has to pay for every mistake made by the language designers, and that's already a sizeable price for C++ to pay, "ABI: Now or never" spells some of that out and we don't want to join them.
I suffered with Java from
Any, Maven and Gradle (the oldest is the the best). After reading about GNU Autotools I was wondering why the C/C++ folks still suffer? Right at that time Meson appeared and I skipped the suffering.
* No XML
* Simple to read and understand
* Simple to manage dependencies
* Simple to use options
Meson merges the crappy state of C/C++ tooling with something like Cargo in the worst way possible: by forcing you to handle the complexity of both. Nothing about Meson is simple, unless you're using it in Rust, in which case you're better off with Cargo.
In C++ you don't get lockfiles, you don't get automatic dependency install, you don't get local dependencies, there's no package registry, no version support, no dependency-wide feature flags (this is an incoherent mess in Meson), no notion of workspaces, etc.
Compared to Cargo, Meson isn't even in the same galaxy. And even compared to CMake, Meson is yet another incompatible incremental "improvement" that offers basically nothing other than cute syntax (which in an era when AI writes all of your build system anyway, doesn't even matter). I'd much rather just pick CMake and move on.
Build system generators (like Meson, autotools, CMake or any other one) can't solve programming language module and packaging problems, even in principle. So, it's not clear what your argument is here.
> I’m still surprised how people ignore Meson. Please test it :)
I did just that a few years ago and found it rather inconvenient and inflexible, so I went back to ignoring it. But YMMV I suppose.
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.
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.
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.
"Failed idea" gives modules too much credit. Outside old codebases, almost no one outside C++ diehards have the patience for the build and tooling circuss they create, and if you need fast iteration plus sane integration with existing deps, modules are like trading your shoes for roller skates in a gravel lot. Adopting them now feels like volunteering to do tax forms in assembbly.
> Second, conforming compiler and standard library implementations are coming quickly. Throughout the development of C++26, at any given point both GCC and Clang had already implemented two-thirds of C++26 features. Today, GCC already has reflection and contracts merged in trunk, awaiting release.
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.
Seeing that pic at the top of the article, and reflecting on my own experiences with rust: It is wild just how male-centric systems programming languages are. I'm from a career backround that's traditionally male-dominated (military aviation), but the balance is far more skewed among C, C++ and Rust developers.
Please don't use Hacker News as a religious or ideological battleground. It tramples curiosity. Please don't pick the most religiously/ideologically provocative thing in an article or post to complain about in the thread. Find something interesting to respond to instead.
This is interesting! People ignoring this, I think, is also interesting on its own. I respect if other people disagree, but that's my 2c. I think our overton windows may not agree here, but I think this is part of the value of discussions with other humans.
Are you a moderator? The directive tone of this post is as if from an authority figure, but, but I do not believe you are one.
I do not believe there is anything about a religious or ideological background here. Could you please clarify?
I also believe it is your post that could be more accurately described as trampling curiosity; I believe there is a role reversal, in that I think your comment is a better description for trampling curiosity than the post your are responding. I'm not trying to be snarky - I'm curious how you came to those conclusions.
Contracts feel like the right direction but the wrong execution timeline. The Ada/SPARK model shows how powerful contracts become when they feed into static verification — but that took decades of iteration on a language with far cleaner semantics. Bolting that onto C++ where UB is load-bearing infrastructure is a different beast entirely. The real risk isn't complexity for complexity's sake — it's that a "minimum viable" contracts spec gets locked in, and then the things that would actually make it useful for proof assistants become impossible to retrofit because they'd break the v1 semantics. Bjarne's concern about "incomplete" is more worrying to me than "bloated."
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.
C++ contracts standardizes what people already do in C++. Where is the complexity in that? It removes the need to write your own implementation because the language provides a standard interoperable one.
An argument can be made that C++26 features like reflection add complexity but I don't follow that argument for contracts.
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.
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.
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.
The devil is in the details, because standardization work is all about details.
From my outside vantage point, there seems to be a few different camps about what is desired for contracts to even be. The conflict between those groups is why this feature has been contentious for... a decade now?
Some of the pushback against this form of contracts is from people who desire contracts, but don't think that this design is the one that they want.
I mean... it's C++. The complexity budget is like the US government's debt ceiling.
Without a significant amount of needed context that quote just sounds like some awkward rambling.
Also almost every feature added to C++ adds a great deal of complexity, everything from modules, concepts, ranges, coroutines... I mean it's been 6 years since these have been standardized and all the main compilers still have major issues in terms of bugs and quality of implementation issues.
I can hardly think of any major feature added to the language that didn't introduce a great deal of footguns, unintended consequences, significant compilation performance issues... to single out contracts is unusual to say the least.
The "erroneous behavior" redefinition for reads of uninitialized variables is really interesting: https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2024/p27...
It does have a runtime cost. There's an attribute to force undefined behavior on read again and avoid the cost:
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.
Biggest open question is whether the small changes to the module system in this standard will actually lead to more widespread adoption
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.
To me, the most important feature of Cargo isn't even the dependency management but that I don't ever need to tell it which files to compile or where to find them. The fact that it knows to look for lib.rs or main.rs in src and then recursively find all my other modules without me needing to specify targets or anything like that is a killer feature on its own IMO. Over the past couple of years I've tried to clone and build a number of dotnet packages for various things, but for an ecosystem that's supposedly cross-platform, almost none of them seem to just work by default when I run `dotnet build` and instead require at least some fixes in the various project files. I don't think I've ever had an issue with a Rust project, and it's hard not to feel like a big part of that is because there's not really much configuration to be done. The list of dependencies is just about the only thing in there that effects the default build; if there's any other configuration other than that and the basic metadata like the name, the repo link, the license, etc., it almost always will end up being specifically for alternate builds (like extra options for release builds, alternate features that can be compiled in, etc.).
For me the lack of dependency hell until I hit a c/c++ component somewhere in the build is the real winner.
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.
Speedy convenience beats absolute correctness anyday. Humans are not immortal and have finite amount of time for life and work. If convenience didn't matter, we would all still be coding in assembly or toggling hardware switches.
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.
It's not true that Rust rejects "the notion of a stable ABI". Rust rejects the C++ solution of freeze everything and hope because it's a disaster, it's less stable than some customers hoped and yet it's frozen in practice so it disappoints others. Rust says an ABI should be a promise by a developer, the way its existing C ABI is, that you can explicitly make or not make.
Rust is interested in having a properly thought out ABI that's nicer than the C ABI which it supports today. It'd be nice to have say, ABI for slices for example. But "freeze everything and hope" isn't that, it means every user of your language into the unforeseeable future has to pay for every mistake made by the language designers, and that's already a sizeable price for C++ to pay, "ABI: Now or never" spells some of that out and we don't want to join them.
I would suggest importing binaries and metadata is going to be faster than compiling all the source for that.
>There are of course good ways of building C++, but those are the exception rather than the standard.
What are the good ways?
I’m still surprised how people ignore Meson. Please test it :)
https://mesonbuild.com/
And Mesons awesome dependency handling:
https://mesonbuild.com/Dependencies.html
https://mesonbuild.com/Using-the-WrapDB.html#using-the-wrapd...
https://nibblestew.blogspot.com/2026/02/c-and-c-dependencies...
I suffered with Java from Any, Maven and Gradle (the oldest is the the best). After reading about GNU Autotools I was wondering why the C/C++ folks still suffer? Right at that time Meson appeared and I skipped the suffering.
Feel free to extend WrapDB.Meson merges the crappy state of C/C++ tooling with something like Cargo in the worst way possible: by forcing you to handle the complexity of both. Nothing about Meson is simple, unless you're using it in Rust, in which case you're better off with Cargo.
In C++ you don't get lockfiles, you don't get automatic dependency install, you don't get local dependencies, there's no package registry, no version support, no dependency-wide feature flags (this is an incoherent mess in Meson), no notion of workspaces, etc.
Compared to Cargo, Meson isn't even in the same galaxy. And even compared to CMake, Meson is yet another incompatible incremental "improvement" that offers basically nothing other than cute syntax (which in an era when AI writes all of your build system anyway, doesn't even matter). I'd much rather just pick CMake and move on.
Build system generators (like Meson, autotools, CMake or any other one) can't solve programming language module and packaging problems, even in principle. So, it's not clear what your argument is here.
> I’m still surprised how people ignore Meson. Please test it :)
I did just that a few years ago and found it rather inconvenient and inflexible, so I went back to ignoring it. But YMMV I suppose.
> After reading about GNU Autotools
Consider Kitware's CMake.
I didn’t think header only was that bad - now we have a nightmare of incompatible standards and compilers.
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.
No. Modules are a failed idea. Really really hard for me to see them becoming mainstream at this point.
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.
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.
Exactly. C++ is still waiting for its "uv" moment, so until then modules aren't even close to solved.
Can you explain why you think modules are a failed idea? Because not that many use them right now?
Personally I use them in new projects using XMake and it just works.
"Failed idea" gives modules too much credit. Outside old codebases, almost no one outside C++ diehards have the patience for the build and tooling circuss they create, and if you need fast iteration plus sane integration with existing deps, modules are like trading your shoes for roller skates in a gravel lot. Adopting them now feels like volunteering to do tax forms in assembbly.
> Second, conforming compiler and standard library implementations are coming quickly. Throughout the development of C++26, at any given point both GCC and Clang had already implemented two-thirds of C++26 features. Today, GCC already has reflection and contracts merged in trunk, awaiting release.
How far is Clang on reflection and contracts?
I am actually excited for post and pre conditions. I think they are an underused feature in most languages.
Great. C++20 has been my favorite and I was wasn't sure what the standards says since it's been a while. I'll be reading the C++26 standard soon
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.
Yeah I feel the same way. Lots of nice features that would have been helpful 5 years ago before I switched to Rust.
As long as programmers still have to deal with header files, all of this is lipstick on a pig.
You don't on new projects. CMake + ninja has support for modules on gcc, clang, and MSVC.
This should be your default stack on any small-to-medium sized C++ project.
Bazel, the default pick for very large codebases, also has support for C++20 modules.
I don't care until they stop pretending Unicode doesn't exist.
Sadly, transparent hash strings for unordered_map are out.
It is annoying that they didn't just apply this to all containers
I look forwards to getting to make use of this in 2040!
Proper reflection is exciting.
GCC has it marked as 'RESOLVED FIXED' as of about a week and a half ago. So, it's coming.
Also, useful: https://gcc.gnu.org/projects/cxx-status.html
Support in GCC isn't what limits my usage of latest C++ at work.
Seeing that pic at the top of the article, and reflecting on my own experiences with rust: It is wild just how male-centric systems programming languages are. I'm from a career backround that's traditionally male-dominated (military aviation), but the balance is far more skewed among C, C++ and Rust developers.
Please don't use Hacker News as a religious or ideological battleground. It tramples curiosity. Please don't pick the most religiously/ideologically provocative thing in an article or post to complain about in the thread. Find something interesting to respond to instead.
This is interesting! People ignoring this, I think, is also interesting on its own. I respect if other people disagree, but that's my 2c. I think our overton windows may not agree here, but I think this is part of the value of discussions with other humans.
Are you a moderator? The directive tone of this post is as if from an authority figure, but, but I do not believe you are one.
I do not believe there is anything about a religious or ideological background here. Could you please clarify?
I also believe it is your post that could be more accurately described as trampling curiosity; I believe there is a role reversal, in that I think your comment is a better description for trampling curiosity than the post your are responding. I'm not trying to be snarky - I'm curious how you came to those conclusions.