5 ms·

Also a demonstration of how much work other compilers do for you behind the scenes.

Groxx 2y ago
Ehhh... not much more so than how much `npm install` hides. These macros are part of a gigantic tower of absurdity that costs many, many times more than they need to, but we use them because dev time is more valuable than CPU time.
- rerdavies 2y ago
  Dev time spent waiting for compiles is way more expensive than CPU time.
  - hughesjj 2y ago
    Well, depends on how much CPU time we're talking about. The Linux kernel is one of the few cases where just the sheer scale of instances may make a difference
  - Groxx 2y ago
    And way, way, WAY less expensive than a troubleshooting session
jonathrg 2y ago
A compiler for a language with generic types will definitely do less work to implement generic min/max than the C preprocessor has to do in order to perform all the text substitutions generated by these macros.
- asplake 2y ago
  Oh totally! It has the information to do it both properly and efficiently.
usr1106 2y ago
Or a demonstration about the poor state of programming languages in 2024. Of course there are others than C. But not many suitable for writing a kernel. And no obvious choice for what Linux could do today. Of course they are starting with Rust, but nobody can predict when that will make the last C macro unnecessary. Unless your prediction is never...
- pjmlp 2y ago
  Plenty of kernels have been written in other languages, naturally UNIX/POSIX folks can hardly think of something else. Even Linus accepting Rust is kind of interesting, because his C++ rants also apply to plenty of Rust code bases.
  - gary_0 2y ago
    Doesn't Rust's `no_std` make it easy to throw out idioms you can't use (or don't like) and just keep the syntax and most of the tooling? I recall that one of Linus's preconditions for inclusion was that Rust's default of panic!ing on allocation failures had to be overrideable. Whereas C++ tends to make you eat the whole enchilada.
    - pjmlp 2y ago
      C++ compilers have similar options, e.g. VC++ has /kernel, and there is the freestanding standard as well. Also see Embedded C++ as used by macOS IO Kit, which thankfully there isn't a Linus at Apple. Regarding Rust, no_std, doesn't change the npm like dependencies, macro festival (with two ways of doing all kinds of stuff), abstraction party with type driven development, the compile times.
      - tialaramex 2y ago
        The C++ "freestanding" even when the current round of work is completed, is nowhere close to Rust's core. Partly this is because Rust thought about this earlier, and partly it's because of the relationship between C++ and the allocator, having operators for a feature which might not even exist on your target, awkward.

Ehhh... not much more so than how much `npm install` hides. These macros are part of a gigantic tower of absurdity that costs many, many times more than they need to, but we use them because dev time is more valuable than CPU time.

rerdavies 2y ago
Dev time spent waiting for compiles is way more expensive than CPU time.
- hughesjj 2y ago
  Well, depends on how much CPU time we're talking about. The Linux kernel is one of the few cases where just the sheer scale of instances may make a difference
- Groxx 2y ago
  And way, way, WAY less expensive than a troubleshooting session

jonathrg 2y ago

A compiler for a language with generic types will definitely do less work to implement generic min/max than the C preprocessor has to do in order to perform all the text substitutions generated by these macros.

asplake 2y ago
Oh totally! It has the information to do it both properly and efficiently.

usr1106 2y ago

Or a demonstration about the poor state of programming languages in 2024. Of course there are others than C. But not many suitable for writing a kernel. And no obvious choice for what Linux could do today. Of course they are starting with Rust, but nobody can predict when that will make the last C macro unnecessary. Unless your prediction is never...

pjmlp 2y ago
Plenty of kernels have been written in other languages, naturally UNIX/POSIX folks can hardly think of something else. Even Linus accepting Rust is kind of interesting, because his C++ rants also apply to plenty of Rust code bases.
- gary_0 2y ago
  Doesn't Rust's `no_std` make it easy to throw out idioms you can't use (or don't like) and just keep the syntax and most of the tooling? I recall that one of Linus's preconditions for inclusion was that Rust's default of panic!ing on allocation failures had to be overrideable. Whereas C++ tends to make you eat the whole enchilada.
  - pjmlp 2y ago
    C++ compilers have similar options, e.g. VC++ has /kernel, and there is the freestanding standard as well. Also see Embedded C++ as used by macOS IO Kit, which thankfully there isn't a Linus at Apple. Regarding Rust, no_std, doesn't change the npm like dependencies, macro festival (with two ways of doing all kinds of stuff), abstraction party with type driven development, the compile times.
    - tialaramex 2y ago
      The C++ "freestanding" even when the current round of work is completed, is nowhere close to Rust's core. Partly this is because Rust thought about this earlier, and partly it's because of the relationship between C++ and the allocator, having operators for a feature which might not even exist on your target, awkward.