Author here, I posted this in Show HN but someone clearly beat me to it. So I'll repost my blurb from there.
Various patterns for safer C programming have been cargo-culting around the industry for decades. Because the language evolves intentionally slowly, these patterns rarely get folded into the language as first-class constructs and are passed down through the generations in a sort of oral tradition of programming.
lib0xc leverages GNUC extensions and C11 features to codify safer C practices and patterns into real APIs with real documentation and real testing. Reduce your casts to and from `void *` with the `context_t` tagged pointer type. Enable type-checked, deferred function invocation with `call_t`. Interrogate structure descriptors with `struct_field_t`. Stop ignoring `-Wint-conversion` and praying you won't regret it when you assign a signed integer to an unsigned integer and use `__cast_signed_unsigned`. These are just a few of lib0xc's standard-library-adjacent offerings.
lib0xc also provides a basic systems programming toolkit that includes logging, unit tests, a buffer object designed to deal with types, a unified Mach-O and ELF linker set, and more.
Everything in lib0xc works with clang's bounds-safety extensions if they are enabled. Both gcc and clang are supported. Porting to another environment is a relatively trivial effort.
It's not Rust, and it's not type safety, but it's not supposed to be. It's supposed to help you make your existing C codebase significantly safer than it was yesterday.
My employer holds the copyright and has permitted its release under the MIT license.
Two notes: GCC has its "access" attributes which can give you similar bounds safety as clang.
Please see also my experimental library. https://codeberg.org/uecker/noplate/ While I do not had enough time to polish it yet, I think it provides some very nice interfaces with improve type and bounds safety, and are also rather convenient.
Also I wonder what parts are redundant if you have FORTIFY_SOURCE ?
(And thank you for working in this topic. If you continue, please reach out to us)
Does anyone know if clang's "<type> <annotation> <variable-name>" format can be given as "<annotation> <type> <variable-name>"? PREfast has been doing this for over 20 years and it looks like a lot of the clang annotations map directly to PREfast ones, it would allow a vast amount of PREfast-annotated code to be used with clang.
I'll have to give the access attributes a look, I hadn't heard of them. (My team were sitting back on gcc-12, so not up to speed on the latest.)
I think I had seen noplate before -- looks like you're taking advantage of the anonymous struct compatibility changes in C23? Those are going to open up a lot of possibilities. Regardless I'd love to stay in touch -- by "us" do you mean the working group?
> This might be a dumb question, but using this + clang bounds-safety, whats the difference between this and something like Zig or Odin.
I really need to learn more about Zig, but from what I know, there are still worlds of possibilities that a modern, well-designed language offers over something like lib0xc. Zig's ability to evaluate any expression at compile-time is one such example.
But generally, lib0xc gives you bounds-safety everywhere it can. Languages like Zig and Rust give you type-safety to their own degrees, which I think is a superset.
> What do you think C would need in order to reach the user experience of those languages?
Not really having direct user experience, it's hard for me to say. But if I what I can give you is a list of features that would make large parts of lib0xc irrelevant:
1. Protocols/traits
2. Allocating from a caller's stack frame (think, returning the result of `alloca` to the caller)
3. printf format specifiers for stdint.h types and for octet strings
4. Ability to express function parameter lists as structures
5. New sprintf family that returns a value which is always less than or equal to the size passed (no negative values)
Basically, I think that the C standard should be working aggressively to cut down on the use cases for heap allocation and `void *`. And I think that the bounds safety annotations should become first-class language features.
Glad to see you’re still doing great stuff, and also very glad to see your new employer supports such things, especially compared to our old employer! Part of why I retired around the same time you left was because I wanted to make and share things.
Every time I look at how easy for people to use this kind of thing but people tends not to, remind me if so-called "memory safety" is a real concern anyway.
there are no good reasons we don't do this in the standards themselves, C, C++, and POSIX should all be working on editions that add safer APIs and mark unsafe APIs as deprecated, to start a long term migration. we know how to do this, we've had a lot of success with this. there are real engineering concerns, sure, but they're not reasons to not do it. compilers and library chains can retain support for less safe variants for plenty of time.
The reason this wasn't done by the standards committees is that they spent decades refusing to admit there was even a problem they could help fix. And if there was a problem, it was easily avoided by just writing better code. And if writing better code wasn't enough, well it was certainly too expensive to provide as a debug option. And if it wasn't too expensive to provide as a debug option, the implementors should really lead the way first. And on and on.
The C committee at least seems to get it now. The C++ committee still doesn't, led in large part by Bjarne.
This is a misrepresentation based on a misunderstanding on how standardization works. The C standard committee has long recognized the need for better safety and carefully made it possible so that C could be implemented safely. But the process is that vendors implement something and then come together during standardization so that it is compatible, not that the standardization is the government that prescribes top-down what everybody has to do. Vendors did not bother to provide safer C implementations and safety features (such as bounds checking) did not get much attention from users in the past. So I am happy to see that there is now more interest in safety, because as soon as there solutions we can start putting them into the standard.
(We can do some stuff before this, but this is always a bit of a fight with the vendors, because they do not like it at all if we tell them what to do, especially clang folks)
Yup, and its not just the standards committees. Look at TR 24731 as an example, an absolute no-brainer for security adding (shock, horror!) bounds checking to long-standing trouble-prone APIs that's been around for 20 years, and the response from most compiler writers/library authors has been "lalalalala I'm not listening I'm not listening". Even then it only got as far as it did due to relentless pressure from Microsoft, anyone else and it'd have been rejected outright.
Having said that, some of it may be due to "it's from Microsoft, we can't ever use it". I'm actually surprised not to have seen any anti-MS diatribes in the discussion so far.
Anything needs to be demonstrated and used in practice before being included in the standard. The standard is only meant to codify existing practices, not introduce new ideas.
It's up to compiler developers to ship first, standardize later.
That produces a bit of a chicken and egg probablem for a stdlib overhaul. Compilers and libc implementations don't have a strong reason to implement safer APIs, because if it is non-standard then projects that want to be portable won't use it , but it won't get standardized unless they do add safer APIs.
So the best hope is probably for a third party library that has safet APIs to get popular enough that it becomes a de facto standard.
A vast number of C++ programs import C and POSIX headers directly, so the language level distinction you wish to make isn’t all that relevant to the subject matter.
How things change. Imagine Microsoft circa 2000 publishing an MIT-licensed source code library targeting "the competition"'s compilers, and including some light humour ("Embiggen C's Pit of Success") in the docs.
The title looks very promising. I’ve added this library to my to-do list to take a deeper look at it. Using this standart library within restricted safe subset of C++ can be a strong opponent for Zig (at least for myself).
Haven't really verified that it works with C++, but I tried my best to guard the stuff I knew would be problematic with #if __cplusplus. Happy to have a PR that makes C++ happier with it.
People say that kind of thing on HN every now and then. I have no idea why this idea is around, it's a complete fantasy in my opinion. I say this as someone who mostly uses Linux.
I truly hope something like this catches on. There is so much low hanging fruit in both the C and C++ standard libraries. Spatial memory could be 90% solved in both languages by mandating the use of safe interfaces.
This is great. Other things needed for a great C development environment are a standardized build process plus build tools and a standardized packaging system.
What most people forget is that software is meant to be used as part of the system. The rush to adopt packaging tools like npm and cargo prevent standardization of system tools. On debian, installing tools should be as simple as ‘apt install’, but now you have to check what toolchain version you install then download GB of stuff from the internet. And that for each software. Easy deps donwload for devs means maintenance nightmare for admins and users.
Author here. It is not currently in production, but it is part of a project in Azure which will go to production at some point. I'm actually leaving Microsoft next week and fully intend to keep working on it if I can reach an agreement to do so with my new employer.
If an agreement can't be reached with your new employer are you certain that folks at Microsoft will continue maintaining this library? I'd like to experiment with it but have trepidation regarding future development.
> I'm not sure MSVC could compile the GNU extensions used.
The supported platforms only list Linux and Mac. Notably missing from that list is any of the BSDs (not counting what may or may not remain of BSD under the Mac hood).
I just haven't tried it on a BSD. No reason it wouldn't work though. Might require a couple of fixes here and there, but generally the library sticks to standard C stuff and uncontroversial POSIX (in the POSIX target).
Quick question for those who've tried it — does this play with existing C
codebases incrementally, or is it more of a "new project only" situation?
The README didn't make that obvious to me.
It's designed to be incremental. For example, you can do a search for `sprintf` and replace it with `ssprintf`. The function signature is the same. Any instance of printing to a character array just works. Think of the APIs as "the stuff you usually do by hand, but safer".
If you get compiler errors, it means you were printing to a heap-allocated buffer (or a buffer whose bounds you did not know), and you should be propagating bounds and using `snprintf`.
Integer conversion is the same way. If you have something like
int v1;
uint64_t v2;
<stuff happens>
v2 = (uint64_t)v1;
Then you can replace it with
v2 = __cast_signed_unsigned(uint64_t, v1);
and you'll get a runtime trap when v1 is a negative value, meaning you can both enable -Wint-conversion and have defined behavior for when the value in a certain integer type is not representable in another.
Microsoft supports memory safety. Rust is 100% the direction for new projects. But there are existing C codebases that are unlikely to be entirely rewritten in a memory-safe language for various reasons. Such projects can significantly benefit from incremental improvements in memory safety.
Look, C is so simple, you can implement a compiler in under 10K lines of code on a new platform. And then spend the your life dodging bugs and come up with a zoo of bizarre macros to keep you safe.
It's just an excuse not to use safe languages. And adopting it isn't that easy - one need to learn how the new library works or even rewrite old working and tested code with it.
This is a tragically misguided view. There are tons of code bases that aren't going to be rewritten in safe languages for various reasons, be it political or technical. You may or may not agree with those reasons, and you may or may not like that these code bases are important, but the fact remains that these projects exist. Giving them a toolset to adopt a broad set of bounds-safe behavior can only be a good thing.
It's not an excuse to write C forever, only because some embedded platforms have poor support in compilers other than GCC. Embedded developers should do something to force embedded vendors providing something better than a GCC fork or even something more obscure.
Author here, I posted this in Show HN but someone clearly beat me to it. So I'll repost my blurb from there.
Various patterns for safer C programming have been cargo-culting around the industry for decades. Because the language evolves intentionally slowly, these patterns rarely get folded into the language as first-class constructs and are passed down through the generations in a sort of oral tradition of programming.
lib0xc leverages GNUC extensions and C11 features to codify safer C practices and patterns into real APIs with real documentation and real testing. Reduce your casts to and from `void *` with the `context_t` tagged pointer type. Enable type-checked, deferred function invocation with `call_t`. Interrogate structure descriptors with `struct_field_t`. Stop ignoring `-Wint-conversion` and praying you won't regret it when you assign a signed integer to an unsigned integer and use `__cast_signed_unsigned`. These are just a few of lib0xc's standard-library-adjacent offerings.
lib0xc also provides a basic systems programming toolkit that includes logging, unit tests, a buffer object designed to deal with types, a unified Mach-O and ELF linker set, and more.
Everything in lib0xc works with clang's bounds-safety extensions if they are enabled. Both gcc and clang are supported. Porting to another environment is a relatively trivial effort.
It's not Rust, and it's not type safety, but it's not supposed to be. It's supposed to help you make your existing C codebase significantly safer than it was yesterday.
My employer holds the copyright and has permitted its release under the MIT license.
Thanks!
Two notes: GCC has its "access" attributes which can give you similar bounds safety as clang.
Please see also my experimental library. https://codeberg.org/uecker/noplate/ While I do not had enough time to polish it yet, I think it provides some very nice interfaces with improve type and bounds safety, and are also rather convenient.
Also I wonder what parts are redundant if you have FORTIFY_SOURCE ?
(And thank you for working in this topic. If you continue, please reach out to us)
Does anyone know if clang's "<type> <annotation> <variable-name>" format can be given as "<annotation> <type> <variable-name>"? PREfast has been doing this for over 20 years and it looks like a lot of the clang annotations map directly to PREfast ones, it would allow a vast amount of PREfast-annotated code to be used with clang.
I'll have to give the access attributes a look, I hadn't heard of them. (My team were sitting back on gcc-12, so not up to speed on the latest.)
I think I had seen noplate before -- looks like you're taking advantage of the anonymous struct compatibility changes in C23? Those are going to open up a lot of possibilities. Regardless I'd love to stay in touch -- by "us" do you mean the working group?
1 reply →
This might be a dumb question, but using this + clang bounds-safety, whats the difference between this and something like Zig or Odin.
What do you think C would need in order to reach the user experience of those languages?
> This might be a dumb question, but using this + clang bounds-safety, whats the difference between this and something like Zig or Odin.
I really need to learn more about Zig, but from what I know, there are still worlds of possibilities that a modern, well-designed language offers over something like lib0xc. Zig's ability to evaluate any expression at compile-time is one such example.
But generally, lib0xc gives you bounds-safety everywhere it can. Languages like Zig and Rust give you type-safety to their own degrees, which I think is a superset.
> What do you think C would need in order to reach the user experience of those languages?
Not really having direct user experience, it's hard for me to say. But if I what I can give you is a list of features that would make large parts of lib0xc irrelevant:
1. Protocols/traits
2. Allocating from a caller's stack frame (think, returning the result of `alloca` to the caller)
3. printf format specifiers for stdint.h types and for octet strings
4. Ability to express function parameter lists as structures
5. New sprintf family that returns a value which is always less than or equal to the size passed (no negative values)
Basically, I think that the C standard should be working aggressively to cut down on the use cases for heap allocation and `void *`. And I think that the bounds safety annotations should become first-class language features.
14 replies →
> What do you think C would need in order to reach the user experience of those languages?
- A better, cross platform build system.
- Generics
- Ergonomic compile time metaprogramming (zig's comptime, rust's macro system, etc)
- Closures - or at least lambdas.
- The ability to return multiple values - eg tuples
- Sum types.
- A built in way to return an error | value from a function
- Defer / Rust's Drop
C is anaemic.
Because it is C not Zig/Odin. The mental/ecosystem cost to use a new language is way way under-estimated in most cases.
1 reply →
Glad to see you’re still doing great stuff, and also very glad to see your new employer supports such things, especially compared to our old employer! Part of why I retired around the same time you left was because I wanted to make and share things.
Every time I look at how easy for people to use this kind of thing but people tends not to, remind me if so-called "memory safety" is a real concern anyway.
there are no good reasons we don't do this in the standards themselves, C, C++, and POSIX should all be working on editions that add safer APIs and mark unsafe APIs as deprecated, to start a long term migration. we know how to do this, we've had a lot of success with this. there are real engineering concerns, sure, but they're not reasons to not do it. compilers and library chains can retain support for less safe variants for plenty of time.
The reason this wasn't done by the standards committees is that they spent decades refusing to admit there was even a problem they could help fix. And if there was a problem, it was easily avoided by just writing better code. And if writing better code wasn't enough, well it was certainly too expensive to provide as a debug option. And if it wasn't too expensive to provide as a debug option, the implementors should really lead the way first. And on and on.
The C committee at least seems to get it now. The C++ committee still doesn't, led in large part by Bjarne.
This is a misrepresentation based on a misunderstanding on how standardization works. The C standard committee has long recognized the need for better safety and carefully made it possible so that C could be implemented safely. But the process is that vendors implement something and then come together during standardization so that it is compatible, not that the standardization is the government that prescribes top-down what everybody has to do. Vendors did not bother to provide safer C implementations and safety features (such as bounds checking) did not get much attention from users in the past. So I am happy to see that there is now more interest in safety, because as soon as there solutions we can start putting them into the standard.
(We can do some stuff before this, but this is always a bit of a fight with the vendors, because they do not like it at all if we tell them what to do, especially clang folks)
5 replies →
Yup, and its not just the standards committees. Look at TR 24731 as an example, an absolute no-brainer for security adding (shock, horror!) bounds checking to long-standing trouble-prone APIs that's been around for 20 years, and the response from most compiler writers/library authors has been "lalalalala I'm not listening I'm not listening". Even then it only got as far as it did due to relentless pressure from Microsoft, anyone else and it'd have been rejected outright.
Having said that, some of it may be due to "it's from Microsoft, we can't ever use it". I'm actually surprised not to have seen any anti-MS diatribes in the discussion so far.
Despite all security denial attitude, WG21 is doing much better than WG14.
Still looking forward to the day C supports something like std::string, std::string_view, std::span, std:;array.
Which starting with C++26 finally have a standards compliant story about having bounds checks enabled by default.
The C charter has a rule of "no invention".
Anything needs to be demonstrated and used in practice before being included in the standard. The standard is only meant to codify existing practices, not introduce new ideas.
It's up to compiler developers to ship first, standardize later.
That produces a bit of a chicken and egg probablem for a stdlib overhaul. Compilers and libc implementations don't have a strong reason to implement safer APIs, because if it is non-standard then projects that want to be portable won't use it , but it won't get standardized unless they do add safer APIs.
So the best hope is probably for a third party library that has safet APIs to get popular enough that it becomes a de facto standard.
2 replies →
Well, there is Annex K which is based on a previous Microsoft effort. Almost universally it is considered terrible and few people implemented it.
Immediately what I thought of when I saw /microsoft.
Not all of the APIs were brain-dead. They just ignored all previous developments and in the proposal they didn't even remove the C++-related language.
There are only two kinds of standards: ones that prioritize stability and backwards compatibility over usefulness and security, and ones nobody uses.
C and POSIX aren't related to C++ at all.
A vast number of C++ programs import C and POSIX headers directly, so the language level distinction you wish to make isn’t all that relevant to the subject matter.
How things change. Imagine Microsoft circa 2000 publishing an MIT-licensed source code library targeting "the competition"'s compilers, and including some light humour ("Embiggen C's Pit of Success") in the docs.
Interesting. I'll be studying this later tonight so I can apply it to my C projects. Especially clang's -fbounds-safety.
The title looks very promising. I’ve added this library to my to-do list to take a deeper look at it. Using this standart library within restricted safe subset of C++ can be a strong opponent for Zig (at least for myself).
Haven't really verified that it works with C++, but I tried my best to guard the stuff I knew would be problematic with #if __cplusplus. Happy to have a PR that makes C++ happier with it.
Thanks for the reply. Noted :)
At the very least, It's a treasure trove of more advanced c design patterns that are worth knowing.
As the readme describes it as basically established industry patterns passed down through word of mouth.
I find It's difficult to find deeper level C programming techniques like these normally.
Interesting that a project from Microsoft doesn't support MSVC or Windows.
I suspect in 20 years Windows will be a Linux distribution with a compatibility layer.
People say that kind of thing on HN every now and then. I have no idea why this idea is around, it's a complete fantasy in my opinion. I say this as someone who mostly uses Linux.
2 replies →
Unfortunate naming. I thought this was about https://libxc.gitlab.io/ but there's an extra '0' in the name here.
I truly hope something like this catches on. There is so much low hanging fruit in both the C and C++ standard libraries. Spatial memory could be 90% solved in both languages by mandating the use of safe interfaces.
This is great. Other things needed for a great C development environment are a standardized build process plus build tools and a standardized packaging system.
I think most people who are into c that I’ve met quite like header only libraries. Copy paste as a package manager does have its benefits.
I mostly just install a -dev package on Linux and I am done.
2 replies →
The Elf interface is a standardised packaging system.
I do NOT want a package manager in my c code. I'm perfectly content with cloning a git repo from my cmake script.
And there is plenty to choose from if you don't like one or another build system.
Thanks! I agree, a better build story for C projects is desperately needed.
What most people forget is that software is meant to be used as part of the system. The rush to adopt packaging tools like npm and cargo prevent standardization of system tools. On debian, installing tools should be as simple as ‘apt install’, but now you have to check what toolchain version you install then download GB of stuff from the internet. And that for each software. Easy deps donwload for devs means maintenance nightmare for admins and users.
Because that's precisely what is needed: an easy way to ship dependency malware like npn, pip, cargo, etc.
Like it or not, having a little bit of friction prevents pulling in packages with thousands of transitive dependencies.
I'm curious – is MSFT using this in production, or is this a "20% time" project? I'm not sure MSVC could compile the GNU extensions used.
Author here. It is not currently in production, but it is part of a project in Azure which will go to production at some point. I'm actually leaving Microsoft next week and fully intend to keep working on it if I can reach an agreement to do so with my new employer.
If an agreement can't be reached with your new employer are you certain that folks at Microsoft will continue maintaining this library? I'd like to experiment with it but have trepidation regarding future development.
1 reply →
> I'm not sure MSVC could compile the GNU extensions used.
The supported platforms only list Linux and Mac. Notably missing from that list is any of the BSDs (not counting what may or may not remain of BSD under the Mac hood).
I just haven't tried it on a BSD. No reason it wouldn't work though. Might require a couple of fixes here and there, but generally the library sticks to standard C stuff and uncontroversial POSIX (in the POSIX target).
Quick question for those who've tried it — does this play with existing C codebases incrementally, or is it more of a "new project only" situation? The README didn't make that obvious to me.
It's designed to be incremental. For example, you can do a search for `sprintf` and replace it with `ssprintf`. The function signature is the same. Any instance of printing to a character array just works. Think of the APIs as "the stuff you usually do by hand, but safer".
If you get compiler errors, it means you were printing to a heap-allocated buffer (or a buffer whose bounds you did not know), and you should be propagating bounds and using `snprintf`.
Integer conversion is the same way. If you have something like
int v1; uint64_t v2;
<stuff happens>
v2 = (uint64_t)v1;
Then you can replace it with
v2 = __cast_signed_unsigned(uint64_t, v1);
and you'll get a runtime trap when v1 is a negative value, meaning you can both enable -Wint-conversion and have defined behavior for when the value in a certain integer type is not representable in another.
Is there anything in here for something like a "slice" or dynamically sized array that carries its length along with it?
Just use compiler option -std=c++20 and use std::span. Don't try reinventing it in C.
If someone needs more than C provides, why on earth would they choose C++?
No rational person is going to want to have to deal with 10x the number of foot guns.
Literally anything when moving from C is better than C++.
5 replies →
std span is not bounds checked.
1 reply →
I thought Microsoft adopted Rust. Are they back pedaling?
Microsoft supports memory safety. Rust is 100% the direction for new projects. But there are existing C codebases that are unlikely to be entirely rewritten in a memory-safe language for various reasons. Such projects can significantly benefit from incremental improvements in memory safety.
Look, C is so simple, you can implement a compiler in under 10K lines of code on a new platform. And then spend the your life dodging bugs and come up with a zoo of bizarre macros to keep you safe.
You forgot the part where you have to read an 800-page document that costs 250€ to access.
This stuff is amongst my favourite type of engineering.
Practical. Useful. Not sexy. (I am only one of those.)
Bravo!
Hell, I aim to be all of those.
Not sexy? Yeah, I can manage that one too.
This is very cool!
It's just an excuse not to use safe languages. And adopting it isn't that easy - one need to learn how the new library works or even rewrite old working and tested code with it.
This is a tragically misguided view. There are tons of code bases that aren't going to be rewritten in safe languages for various reasons, be it political or technical. You may or may not agree with those reasons, and you may or may not like that these code bases are important, but the fact remains that these projects exist. Giving them a toolset to adopt a broad set of bounds-safe behavior can only be a good thing.
If i cannot use GCC i cannot compile to half the embedded platforms i work with on a daily basis.
C remains widespread for unique reasons that not many other languages actually quite grasp.
Using C for a destop application should probably stop being done in light of many more languages more suited for the domain.
But there is no replacement for C in hard embedded systems. And there is no replacement for C in the massive domain of legacy c systems.
It's not an excuse to write C forever, only because some embedded platforms have poor support in compilers other than GCC. Embedded developers should do something to force embedded vendors providing something better than a GCC fork or even something more obscure.
1 reply →
Good thing there are safe languages that compile to C, such as Nim.
1 reply →