An Alternative to Rewriting Memory-Unsafe Code in Rust: the 'Safe C++ Extensions' Proposal (theregister.com) 76
"After two years of being beaten with the memory-safety stick, the C++ community has published a proposal to help developers write less vulnerable code," reports the Register.
"The Safe C++ Extensions proposal aims to address the vulnerable programming language's Achilles' heel, the challenge of ensuring that code is free of memory safety bugs..." Acknowledging the now deafening chorus of calls to adopt memory safe programming languages, developers Sean Baxter, creator of the Circle compiler, and Christian Mazakas, from the C++ Alliance, argue that while Rust is the only popular systems level programming language without garbage collection that provides rigorous memory safety, migrating C++ code to Rust poses problems. "Rust lacks function overloading, templates, inheritance and exceptions," they explain in the proposal. "C++ lacks traits, relocation and borrow checking. These discrepancies are responsible for an impedance mismatch when interfacing the two languages. Most code generators for inter-language bindings aren't able to represent features of one language in terms of the features of another."
Though DARPA is trying to develop better automated C++ to Rust conversion tools, Baxter and Mazakas argue telling veteran C++ developers to learn Rust isn't an answer... The Safe C++ project adds new technology for ensuring memory safety, Baxter explained, and isn't just a reiteration of best practices. "Safe C++ prevents users from writing unsound code," he said. "This includes compile-time intelligence like borrow checking to prevent use-after-free bugs and initialization analysis for type safety." Baxter said that rewriting a project in a different programming language is costly, so the aim here is to make memory safety more accessible by providing the same soundness guarantees as Rust at a lower cost. "With Safe C++, existing code continues to work as always," he explained. "Stakeholders have more control for incrementally opting in to safety."
The next step, Baxter said, involves greater participation from industry to help realize the Safe C++ project. "The foundations are in: We have fantastic borrow checking and initialization analysis which underpin the soundness guarantees," he said. "The next step is to comprehensively visit all of C++'s features and specify memory-safe versions of them. It's a big effort, but given the importance of reducing C++ security vulnerabilities, it's an effort worth making."
"The Safe C++ Extensions proposal aims to address the vulnerable programming language's Achilles' heel, the challenge of ensuring that code is free of memory safety bugs..." Acknowledging the now deafening chorus of calls to adopt memory safe programming languages, developers Sean Baxter, creator of the Circle compiler, and Christian Mazakas, from the C++ Alliance, argue that while Rust is the only popular systems level programming language without garbage collection that provides rigorous memory safety, migrating C++ code to Rust poses problems. "Rust lacks function overloading, templates, inheritance and exceptions," they explain in the proposal. "C++ lacks traits, relocation and borrow checking. These discrepancies are responsible for an impedance mismatch when interfacing the two languages. Most code generators for inter-language bindings aren't able to represent features of one language in terms of the features of another."
Though DARPA is trying to develop better automated C++ to Rust conversion tools, Baxter and Mazakas argue telling veteran C++ developers to learn Rust isn't an answer... The Safe C++ project adds new technology for ensuring memory safety, Baxter explained, and isn't just a reiteration of best practices. "Safe C++ prevents users from writing unsound code," he said. "This includes compile-time intelligence like borrow checking to prevent use-after-free bugs and initialization analysis for type safety." Baxter said that rewriting a project in a different programming language is costly, so the aim here is to make memory safety more accessible by providing the same soundness guarantees as Rust at a lower cost. "With Safe C++, existing code continues to work as always," he explained. "Stakeholders have more control for incrementally opting in to safety."
The next step, Baxter said, involves greater participation from industry to help realize the Safe C++ project. "The foundations are in: We have fantastic borrow checking and initialization analysis which underpin the soundness guarantees," he said. "The next step is to comprehensively visit all of C++'s features and specify memory-safe versions of them. It's a big effort, but given the importance of reducing C++ security vulnerabilities, it's an effort worth making."
Complicate much? (Score:4, Insightful)
"Rust lacks function overloading, templates, inheritance and exceptions,"
They say this as if it's a bad thing.
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They also didn't mention that Rust does have macros (lisp-ish macros, not silly string substitutions like C macros). These are used for many of the things that would be done with templates in C++.
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It is if you want to migrate a C++ application over to something safer. A complete rewrite is not always feasible.
Circle C++ is pretty impressive. I'm glad to see the ideas developed there move into mainstream C++. From what I've seen in Circle, this should dramatically reduce the learning curve for C++ developers.
Re: Complicate much? (Score:5, Insightful)
The only thing unsafe about C++ is letting C coders use it.
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False, just because a human not making errors eliminates a problem, doesn't make the underlying tool unsafe.
Why bother with seatbelts and crumple zones. Just make sure drivers are good!
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C++ IS the seatbelts and crumple zones.
But only if you let it.
Re: Complicate much? (Score:2)
My seatbelts don't have such a thick manual that gets rewritten every 5 years.
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I depend on all of those things. I'm a bit surprised, though, I thought Rust had templates at least.
Rust does have basically all of those things. https://developers.slashdot.or... [slashdot.org]
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Moreover, adding safe extensions to C++ will get manager the stamp they need as "having a safe language" while nothing will be done on the project to actually adhere to these extensions. Migrating your C++ code to these extensions will require a major rewrite of your app, while still not guaranteeing everything is safe in your codebase.
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In practice Rust code will be littered with "unsafe" and questionable dependencies.
I start to believe hat this is all partially driven to avoid product liability: "Nobody can write C/C++ code so we can not be responsible for our mistakes, this will all change in the future with Rust, but please leave us alone for now!" In reality, when you look most mistakes are very basic and as many pointed out, memory safety is just one issue of many. So I do not expect a huge different with Rust.
Re: Complicate much? (Score:2)
Re:Complicate much? (Score:4, Interesting)
Re: Complicate much? (Score:2)
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Yes it is.
Or why do you think I prefer C++ over Rust?
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"Rust lacks function overloading, templates, inheritance and exceptions,"
They say this as if it's a bad thing.
It's also not true, except for function overloading, which isn't really a big issue. Rust absolutely has generics which aren't precisely the same as C++ templates, but accomplish the same tasks. If you include Rust's macros, the result is actually much more powerful than C++ templates (and, no, Rust's macros aren't anything like the simplistic string substitution C/C++ provide). Rust's traits provide all of the really important benefits of inheritance, but avoid most of the pitfalls. The one thing C++ inhe
I think they just hate how physical memory works.. (Score:2)
2 dimensional silicon memory binary memory will not manage itself. And you can't just assume that on that vast plane a byte will stop and start where you want it to. You have to know. Isn't that how the bad guys do it? Knowing where your byte is AFTER you ASSUME it its somewhere else?
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Instead of training them, you just give them Rust or Python and don't worry about it.
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could you speak on this more? I would love some more of this word salad
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could you speak on this more? I would love some more of this word salad
I think it's a Star Trek: The Next Generation reference, the Android "Data" explaining a problem to someone. :-)
Why are we primarily targeting memory issues? (Score:3)
It seems to me from CVE breakdown by type [cvedetails.com] that memory issues result in a somewhat small subset of total CVEs. Where is this concerted effort of making more languages police the programmers' use of memory coming from? Sees like XSS is much more of a culprit in regard to vulnerabilities, despite modern browsers' locking down of XSS interactions. Is it because the languages are trying to adapt to corporations seeking cheaper and cheaper programmers?
Re:Why are we primarily targeting memory issues? (Score:5, Insightful)
1: list out what you are protecting - a secret, authentication for something else to do something, control to something
2: list out what your opponents are, their motivation, their resources, their access - is it a script kiddy, a foreign government, do they have physical access
3: list what the attacks could be - physically damaging your device, bypassing it, signal blocking, replaying an old command...
4: come up with mitigations to all the attacks. ***All mitigations must trace back to an attack ****
5: evaluate your system. How complicated is it? Could the things you are protecting be individually protected or is everything protected at once? Do your mitigations actually mitigate the attacks they are mapped to? Have you missed any attacks and can you accept those vulnerabilities? Go back to how complicated your system is. If you can't explain it, then no single person can take ownership of the security and you will have attacks with no mitigations.
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The real bugs are in people completely missing what the attack is and having no mitigations at all against the attack.
...
4: come up with mitigations to all the attacks. ***All mitigations must trace back to an attack ****
In that case, what are all of your mitigations against unchecked bounds, use after free, double free, dereferencing invalid pointers, and their related cousins, dirty reads, and dirty writes?
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Those aren't attacks, retard.
Go away.
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The STL. And good design practices.
Seriously. Whenever I hear about C++ and memory bugs, I think back to 1998 when that was seriously an issue. Of the following types of memory failures you mentioned:
I have found none in the code my collea
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That's a real risk assessment (often formalised into various methods) and essentially I think it is right.
It then becomes a huge pain getting people to do it. So I think there's some psychological or mental state thing which gets in the way.
It may just be that when writing code, people are using a mental state that's focussed on discrete things to achieve a specific target, whereas risk is all about uncertainty, and having to handle multiple uncertainties and multiple novelties. It just makes people's brain
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Memory issues can be found by noobs running scans on executables.
No, they can't. Valgrind, etc. can find many issues, but not all. Valgrind + fuzzing can find a lot more, but will never flush them all out.
The real bugs are in people completely missing what the attack is and having no mitigations at all against the attack.
Sure, memory safety is orthogonal to proper threat modeling and secure design. You need both. All of the effort in the world applied to threat modeling won't protect you from memory safety bugs, nor will using the best memory safety tools protect you from insecure design.
Re: Why are we primarily targeting memory issues? (Score:3)
Xss is language agnostic.
I dont see how the two are comparable in the context of compilers and languages
Re: Why are we primarily targeting memory issues? (Score:4, Interesting)
I'm aware of that. What I was alluding to was that perhaps fixing buffer overrun and such issues via changes to languages is an effort to make programming more fool-proof and that it may result in possible lower wages for better programmers by giving sub-par programmers the tools to compete on a more level playing field.
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... it may result in possible lower wages for better programmers by giving sub-par programmers the tools to compete on a more level playing field.
So your argument is that making programming easier is bad because it increases competition?
By that logic, we should code everything in assembly and COBOL. That will raise salaries through the roof.
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Re:Why are we primarily targeting memory issues? (Score:5, Informative)
Cross-site scripting attacks do not generally involve issues that the C++ designers can address. They are, at best, logic errors on the part of browser programmers who didn't implement their APIs according to their own specs.
Now, disregarding XSS, the total number of overflow and memory corruption bugs exceeds all the others combined: 37695 vs 33290 in the years 2014 to 2024—those two categories add up to 38% of all CVEs in the time period. That's a lot of wasted labor brought on by a reckless corner-cutting decision made 50 years ago by Ken Thompson and Dennis Ritchie, who thought PL/I's length-tagged strings were too much work for their cruddy little hand-me-down PDP-7 to handle.
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Languages are trying to evolve toward cheaper development which is not quite the same as cheaper programmers. If you look at metrics like lines of code per day, they are largely unchanged over time. Good programmers go at a certain rate. Maybe bad ones make more LoC per day or maybe they make less, I don't
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It seems to me from CVE breakdown by type that memory issues result in a somewhat small subset of total CVEs.
Memory corruption CVEs tend to dominate the most critical vulnerabilities, though. They're the primary vector for arbitrary code execution exploits.
malloc_safe_safer_safeforrealthistime() (Score:3)
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let's call this _safe_safe_for_realzies_this_time_i_swear :p
this seems more involved and I am glad some are getting the message, potentially can be a good thing
A borrow checker for C++ (Score:5, Insightful)
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Definitely. That and other compile-time checks including checking that all enums are handled properly. Circle C++ does all of this. Getting the concepts developed in Circle into the core C++ standard will be highly beneficial. C++ is still complex and crufty, but you can not use the old, complicated stuff in favor of the new safe constructs and syntax. No one should be passing raw pointers around. std:: has contained some powerful reference-counting smart pointers for years now that were a step in the r
Re: A borrow checker for C++ (Score:2)
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This. If the committee would figure out optional references we would have a lot fewer use cases for raw pointers as well.
Re: A borrow checker for C++ (Score:2)
Re: A borrow checker for C++ (Score:2)
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Re:A borrow checker for C++ (Score:4, Interesting)
It feels like they're trying to reinvent rust and just slap the C++ moniker on it so they can say they didn't have to learn a new language.
Besides, the biggest gripe most of them have against rust to begin with IS the borrow checker, and this is despite the fact that they like to pat themselves on the back about how good at RAII they are, and then violate its principles anyways.
Circle C++ does all of this.
One thing I haven't seen any interest in from C++ developers is using optional types and result types. Instead they seem to have a preference for throwing exceptions and then using try/catch blocks, which not only carries a higher runtime penalty but also ends up with more bugs when they either assume a try/catch isn't needed or they don't realize that the library they're hooking into can even throw exceptions. That or they do really horrible things like assume that dereferencing a null pointer because they can't be bothered to check for one will simply seg fault instead of doing potentially much worse things.
In Rust, if you don't explicitly handle every last error condition (even if handling it means telling the compiler to panic there) then your code won't even compile.
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Just to clarify: I am aware of Circle's 'Choice' type.
Re: A borrow checker for C++ (Score:2)
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Neither am I except I like all the alternatives even worse.
They're not really invisible in that you need to assume any function other than noexcept might exit via a throw.
I'm not really that thrilled with the return type being Any. Clearly neither were the designers of Java, but that didn't really work out great either in that it became very boilerplaty. Also, one could argue (and Stroustrup has) that the design of the std::exception class hierarchy was not ideal in practice. I'm coming round on the idea th
Re: A borrow checker for C++ (Score:2)
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It feels like Rust is taking what used to be the domain of a test framework, shoving it into the compiler, and then slapping the "memory safety" moniker on it, and trying to define every other language as "memory unsafe".
look up the definition of a compiler:
https://en.wikipedia.org/wiki/Compiler
"In computing, a compiler is a computer program that translates computer code written in one programming language (the source language) into another language (the target language)."
look up the definition of a softwar
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Indeed. Still, I would say it is a good think to move many of these things into the language / compiler.
But the "memory-safe Rust" vs "memory-unsafe C/C++" marketing is annoyingly misleading.
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One thing I haven't seen any interest in from C++ developers is using optional types and result types.
Std::optional exists just fine.
Instead they seem to have a preference for throwing exceptions and then using try/catch blocks,
It's nice, it avoids spamming if(err) return errr; everywhere.
which not only carries a higher runtime penalty
LOWER runtime penalty. If you don't throw an exception it incurs no cost at all unlike error codes.
but also ends up with more bugs when they either assume a try/catch isn't n
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I don't really have a lot of sympathy for the position of "we have language feature X but we say it's not X and tell you to not use it except when you should".
panic is the same as C++ exceptions to the point that the only implementation of Rust uses the Itanium ABI and you can throw from Rust and catch in C++, or throw from C++ and catch_unwind in Rust. C++ exceptions are only "meant" to be used in exceptional circumstances (hence the name), sticking "very" in front of that lot for Rust exceptions (ahem pa
Re: A borrow checker for C++ (Score:2)
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which not only carries a higher runtime penalty
LOWER runtime penalty. If you don't throw an exception it incurs no cost at all unlike error codes.
This is simply incorrect.
Compiling C++ with exceptions enabled adds a lot of boilerplate to every compiled function, specifically to deal with the potential need to properly unwind the stack at any point. In the compiled code the run-time cost of having exceptions enabled isn't appreciably different from having "if (err)" scattered throughout the code, though the explicit error handling code often makes the code much less readable. Rust addresses this with a bit of syntactic sugar which boils the whole
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C++ has "zero overhead" exceptions since minimum 30 years.
And yes, we prefer exceptions over "double type" return results where we have to write an if after every function/method call.
In C++ dereferencing a null pointer, can be converted into throwing an exception instead. I guess everyone is doing that, no idea though.
Re: A borrow checker for C++ (Score:2)
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One thing I haven't seen any interest in from C++ developers is using optional types and result types.
They're extremely common in the C++ code I see. std::optional is used everywhere, and result types are common in code that doesn't use exceptions.
I agree 100% (Score:5, Funny)
The one thing that will make C++ easier to learn and understand, more welcoming, more straightforward, and will eliminate fragmentation and baggage, is just one more extension.
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lol, since you seem to like extensions, I extend to you my sympathy :p
Legitimately good idea. (Score:4, Interesting)
Even Rust has unsafe blocks where you can use unsafe features, so it's actually not as much of a stretch to imagine a memory safe version of C++ as you'd think. We already have examples of memory safe languages that are C++-like or C++-inspired (Java, C#), so I think it's actually reasonable to try to adopt the features of memory safe languages. C++ is known for having everything and the kitchen sink, so why not adopt both Rust-like memory safety options as well as garbage collection, and let users choose?
These are just ideas I'm throwing out here, my main message is that this is that I like this line of thinking, and I think it could be a step in the right direction. Sure, it has a lot of issues that still need to be addressed (like how do you enforce safety for users who want to enforce it?), but I just feel like there's some good core thinking behind this.
Re: Legitimately good idea. (Score:2)
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C++ already has memory safety. All you have to do is always use smart pointers and other standard library classes for lists, etc and your are 99% of the way there. Make a compiler reject any kind of raw pointer use and that's most of it solved.
Adding borrow checking also helps, as the Safe C++ proposal suggests. For one example (and the first one mentioned in the Safe C++ doc), using smart pointers doesn't help if you do something to invalidate iterators, for example... and many iterators are not smart enough to simply stop working if invalidated. And even those that are force you to diagnose the problem at runtime, whereas a borrow checker can do it at compile time.
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Managed C++ is a subset of C++.
That is why no one is using it.
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Microsoft already did this a long time ago, have a look at Managed C++ [wikipedia.org]. It's basically nothing new.
Not really. Managed C++ is basically C++ for .NET, which means it's garbage-collected and depends on the .NET runtime. You couldn't use Managed C++, for example, to write Linux kernel modules. The proposed Safe C++ does not have those sorts of dependencies and would be usable for low-level systems code, where C, normal C++ or Rust would be usable.
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You can just link a garage collector library to your C++ program.
Boehm, comes to mind.
But that does not solve Array overruns and other things.
The linux kernel (Score:2)
Linus has been very vocal [cat-v.org] about his dislike for C++.
But it would be a lot easier for the kernel to adopt safe C++ than rust, and they added support for rust for its safety features.
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But it would be a lot easier for the kernel to adopt safe C++ than Rust
Would it? Why do you think that? I think it's basically the same problem.
Dr. Dobbs wrote on this years ago (Score:2)