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> I almost never see those programmers actually writing a "reasonable"/"friendly"/"boring" C compiler. Why is no one willing to put their ~money~ time where the

by bsder 2y ago

> I almost never see those programmers actually writing a "reasonable"/"friendly"/"boring" C compiler. Why is no one willing to put their ~money~ time where their mouth is? Because it is not much harder to simply write a new language and you can discard all the baggage? Lots of verbiage gets spilled about undefined behavior, but things like the preprocessor and lack of "slices" are way bigger faults of C. Proebsting's Law posits that compiler optimizations double performance every 20 years. That means that you can implement the smallest handful of compiler optimizations in your new language and still be within a factor of 2 of the best compilers. And people are doing precisely that (see: Zig, Jai, Odin, etc.).

WalterGillman 2y ago
I'm willing to write a C compiler that detects all undefined behavior but instead of doing something sane like reporting it or disallowing it just adds the code to open a telnet shell with root privileges. Can't wait to see the benchmarks.
- muldvarp 2y ago
  > doing something sane like reporting it or disallowing it This is only possible if you check for it at runtime and that's a tradeoff most C programmers don't like.
  - WalterGillman 2y ago
    I was thinking more along the lines of detectable instances with compiler introducing "optimizations", but as a C "programmer" I do not mind bounds checks and any other runtime improvements that stay true to the language. If it's implementation-defined that you can turn them off when you're building for the PDP11, I'm sold.
    - muldvarp 2y ago
      Compilers already warn when they detect _unconditional_ undefined behavior. They just don't warn on _conditional_ undefined behavior because doing so would introduce far too many warnings. Exploiting undefined behavior for optimization only requires local analysis, detecting whether that undefined behavior arises (either unconditionally or at all) requires global analysis. To put it differentially: The compiler often simply doesn't know whether the undefined behavior arises, it only knows that the optimization it introduces is valid anyway.

by bsder 2y ago

WalterGillman 2y ago

I'm willing to write a C compiler that detects all undefined behavior but instead of doing something sane like reporting it or disallowing it just adds the code to open a telnet shell with root privileges. Can't wait to see the benchmarks.

muldvarp 2y ago
> doing something sane like reporting it or disallowing it This is only possible if you check for it at runtime and that's a tradeoff most C programmers don't like.
- WalterGillman 2y ago
  I was thinking more along the lines of detectable instances with compiler introducing "optimizations", but as a C "programmer" I do not mind bounds checks and any other runtime improvements that stay true to the language. If it's implementation-defined that you can turn them off when you're building for the PDP11, I'm sold.
  - muldvarp 2y ago
    Compilers already warn when they detect _unconditional_ undefined behavior. They just don't warn on _conditional_ undefined behavior because doing so would introduce far too many warnings. Exploiting undefined behavior for optimization only requires local analysis, detecting whether that undefined behavior arises (either unconditionally or at all) requires global analysis. To put it differentially: The compiler often simply doesn't know whether the undefined behavior arises, it only knows that the optimization it introduces is valid anyway.