5 ms·

What difference does that make for an end user? You have two copies of the same OS on the 2 PCs (same hardware) but one compiled on gcc, the other on LLVM/clang

What difference does that make for an end user? You have two copies of the same OS on the 2 PCs (same hardware) but one compiled on gcc, the other on LLVM/clang. How will this affect me? What differences I will notice? Better performance? Like real world performance

deleted 7y ago
[deleted]
nickpsecurity 7y ago
The only benefit I can think of is increased security now or over time. Most people developing compiler-based mitigations work on LLVM. Especially the practical ones. HardenedBSD is an example of a project making use of them. SVA is an example of one that might be applied to Linux: https://github.com/jtcriswell/SVA https://github.com/jtcriswell/SVA
- AsyncAwait 7y ago
  More research style projects are indeed based on LLVM, but GCC is extremely serious about security too, (and contains more Linux-specific optimizations & code too). For the end user, it comes down to - do you care about copyleft and what FSF/Stallman are advocating for, or do you just want a free (as in beer) code, (LLVM). I'd argue as a user, the GPL cares more about your freedom, so unless you have a specific reason not to use GCC, go with that over LLVM, (yes, am aware of the exception re binaries compiled with GCC not having to themselves be GPL).
  - lone_haxx0r 7y ago
    I'm a freedom-focused user that prefers BSD licenses.
- meruru 7y ago
  This is possibly a silly question but... when it comes to the threat of backdoor vulnerabilities inserted in the compiler itself, which would you say is the safer option? From what I can tell LLVM has a simpler codebase so that's a point in its favor, but I think GCC being a GNU project is less likely to have developers who could be pressured to insert malicious code. Am I crazy in worrying about this? I know initiatives like reproducible builds are supposed to help solve that kind of threat, but it's still not clear to me how it all fits together.
  - AsyncAwait 7y ago
    > GCC being a GNU project is less likely to have developers who could be pressured to insert malicious code. I'd agree with this, since GNU projects tend to have at least some devs who are in it for the ideology.
  - ori_b 7y ago
    > From what I can tell LLVM has a simpler codebase so that's a point in its favor That may have been true at one point, but I don't think it is any more.
    - meruru 7y ago
      Are you referring to the first or the second part of that sentence?
      - ori_b 7y ago
        The simplicity of the LLVM source. Edited for clarity.
        Conan_Kudo 7y ago
        LLVM sources are equally, if not more so, complicated than GCC's sources. To make matters worse, LLVM functionality is broken up into dozens of libraries, so there's a fair bit more tracing that needs to be done to understand what's going on in Clang vs GCC.
  - nickpsecurity 7y ago
    "when it comes to the threat of backdoor vulnerabilities inserted in the compiler itself, which would you say is the safer option?" Neither. They're equally unsafe with relatively low risk of this specific attack outside maybe distribution. Although clever idea, AsyncAwait's ideology doesn't work since spies will pose as them. Good news is the Karger compiler-compiler attack has only happened two or three times that I know of. What's burned projects many more times and most worth worrying about are security-related compiler errors. They transform your code in a way that removes safety/security checks or adds a security problem (eg timing channel). So, the real problem is compiler correctness more than anything. That requires so-called certifying compilers that put lots of effort into ensuring each step or pass is correct. CompCert and CakeML are probably the champions there with formal verification. You could also do rigorous testing, SQLite-style, of each aspect of the compiler on top of using a memory-safe language. If you restrict features, then the bootstrapping can be done in an interpreter written and tested the same way before being ported by hand to designed-for-readability assembly. It didn't stop there, though. Recent work in verification camp is doing compilation designed to be secure despite using multiple, abstraction levels such as source or assembly or mixed languages. Here's a nice survey on that: http://theory.stanford.edu/~mp/mp/Publications_files/a125-patrignani.pdf http://theory.stanford.edu/~mp/mp/Publications_files/a125-pa... The group putting it all together the most is DeepSpec. They have both papers and nice diagrams here: https://deepspec.org/main https://deepspec.org/main
StreamBright 7y ago
There are security implication sometimes. https://twitter.com/dakami/status/668888298677407744?lang=en https://twitter.com/dakami/status/668888298677407744?lang=en
koyote 7y ago
You could theoretically see better real-world performance. As someone who is currently working on very high-performance C++, I have noticed Clang being much more 'confident' in optimising code than its counterparts (especially compared to MSVC++). That being said, in the grand scheme of things any performance improvement would probably only show up on benchmarks.
- agumonkey 7y ago
  Might inspire new implementations if people realize there are some spots that can run faster elsewhere.
- geezerjay 7y ago
  > You could theoretically see better real-world performance. That assertion isn't very realistic. Performance benchmarks comparing gcc and clang are mixed, with performance differences being marginal at best. https://www.phoronix.com/scan.php?page=article&item=gcc9-clang8-hedt https://www.phoronix.com/scan.php?page=article&item=gcc9-cla...

deleted 7y ago

[deleted]

nickpsecurity 7y ago

The only benefit I can think of is increased security now or over time. Most people developing compiler-based mitigations work on LLVM. Especially the practical ones. HardenedBSD is an example of a project making use of them. SVA is an example of one that might be applied to Linux: https://github.com/jtcriswell/SVA https://github.com/jtcriswell/SVA

AsyncAwait 7y ago
More research style projects are indeed based on LLVM, but GCC is extremely serious about security too, (and contains more Linux-specific optimizations & code too). For the end user, it comes down to - do you care about copyleft and what FSF/Stallman are advocating for, or do you just want a free (as in beer) code, (LLVM). I'd argue as a user, the GPL cares more about your freedom, so unless you have a specific reason not to use GCC, go with that over LLVM, (yes, am aware of the exception re binaries compiled with GCC not having to themselves be GPL).
- lone_haxx0r 7y ago
  I'm a freedom-focused user that prefers BSD licenses.
meruru 7y ago
This is possibly a silly question but... when it comes to the threat of backdoor vulnerabilities inserted in the compiler itself, which would you say is the safer option? From what I can tell LLVM has a simpler codebase so that's a point in its favor, but I think GCC being a GNU project is less likely to have developers who could be pressured to insert malicious code. Am I crazy in worrying about this? I know initiatives like reproducible builds are supposed to help solve that kind of threat, but it's still not clear to me how it all fits together.
- AsyncAwait 7y ago
  > GCC being a GNU project is less likely to have developers who could be pressured to insert malicious code. I'd agree with this, since GNU projects tend to have at least some devs who are in it for the ideology.
- ori_b 7y ago
  > From what I can tell LLVM has a simpler codebase so that's a point in its favor That may have been true at one point, but I don't think it is any more.
  - meruru 7y ago
    Are you referring to the first or the second part of that sentence?
    - ori_b 7y ago
      The simplicity of the LLVM source. Edited for clarity.
      - Conan_Kudo 7y ago
        LLVM sources are equally, if not more so, complicated than GCC's sources. To make matters worse, LLVM functionality is broken up into dozens of libraries, so there's a fair bit more tracing that needs to be done to understand what's going on in Clang vs GCC.
- nickpsecurity 7y ago
  "when it comes to the threat of backdoor vulnerabilities inserted in the compiler itself, which would you say is the safer option?" Neither. They're equally unsafe with relatively low risk of this specific attack outside maybe distribution. Although clever idea, AsyncAwait's ideology doesn't work since spies will pose as them. Good news is the Karger compiler-compiler attack has only happened two or three times that I know of. What's burned projects many more times and most worth worrying about are security-related compiler errors. They transform your code in a way that removes safety/security checks or adds a security problem (eg timing channel). So, the real problem is compiler correctness more than anything. That requires so-called certifying compilers that put lots of effort into ensuring each step or pass is correct. CompCert and CakeML are probably the champions there with formal verification. You could also do rigorous testing, SQLite-style, of each aspect of the compiler on top of using a memory-safe language. If you restrict features, then the bootstrapping can be done in an interpreter written and tested the same way before being ported by hand to designed-for-readability assembly. It didn't stop there, though. Recent work in verification camp is doing compilation designed to be secure despite using multiple, abstraction levels such as source or assembly or mixed languages. Here's a nice survey on that: http://theory.stanford.edu/~mp/mp/Publications_files/a125-patrignani.pdf http://theory.stanford.edu/~mp/mp/Publications_files/a125-pa... The group putting it all together the most is DeepSpec. They have both papers and nice diagrams here: https://deepspec.org/main https://deepspec.org/main

StreamBright 7y ago

There are security implication sometimes. https://twitter.com/dakami/status/668888298677407744?lang=en https://twitter.com/dakami/status/668888298677407744?lang=en

koyote 7y ago

You could theoretically see better real-world performance. As someone who is currently working on very high-performance C++, I have noticed Clang being much more 'confident' in optimising code than its counterparts (especially compared to MSVC++). That being said, in the grand scheme of things any performance improvement would probably only show up on benchmarks.

agumonkey 7y ago
Might inspire new implementations if people realize there are some spots that can run faster elsewhere.
geezerjay 7y ago
> You could theoretically see better real-world performance. That assertion isn't very realistic. Performance benchmarks comparing gcc and clang are mixed, with performance differences being marginal at best. https://www.phoronix.com/scan.php?page=article&item=gcc9-clang8-hedt https://www.phoronix.com/scan.php?page=article&item=gcc9-cla...