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I would rather just announce to the compiler what standard version a given piece of code should adhere to (and it's fine if -std=2x doesn't accept older C stand

I would rather just announce to the compiler what standard version a given piece of code should adhere to (and it's fine if -std=2x doesn't accept older C standards except for header declarations - while at it, please remove the 'inline' keyword from the next C standard ;)) To some extent that's already possible with the "-std=..." option of course, but it would be better to also allow changing the standard version within the same compilation unit (at least if it turns out that including headers written in old C standards can't be supported, in that case I would like to wrap a block of #includes with a 'use c89 { ... }'). Random example for why it is important to allow older C versions to compile: I just made a mid-90's assembler for 8-bit CPUs written in C89 work in VSCode via WASM/WASI without requiring any code changes (and yes I've been looking long and hard for an alternative assembler tool which provides the same feature set written more recently without luck, I even considered writing my own assembler from scratch). It would suck if I had to port the code base to a more recent C standard just to make it compile, and (if that would be possible) automatically formatting that code to a more recent C version would introduce a hard "before/after" split in version control.

uecker 3y ago
What is wrong with "inline"? I do not think it is feasible to maintain all language versions in parallel for eternity. What would make porting this code to a newer standard difficult in this specific case?
- flohofwoe 3y ago
  Inline "encourages" moving implementation code into headers instead of only interface declarations, and the inline feature isn't all that useful anymore with LTO anyway. It's a good thing to only have declarations in headers, it simplifies parsing with 3rd party tools (to generate language bindings), and speeds up compilation (see the C++ stdlib headers for the canonical "why is implementation code in headers a bad idea" example). IMHO mixing interface declarations with implementation details was one of the cardinal sins of C++. > What would make porting this code to a newer standard difficult in this specific case? It's pointless busywork, and it's unclear how deep the changes should go (for instance: does it make sense to move C89 variable declaration from the start of scope blocks to their initialization point just because it might potentially be "safer" but touches half of all lines of code?). The code demonstrably works as C89, and any bugs that matter most likely had already been fixed decades ago, also doing large scale syntax changes is just noise in version control which makes bug fixing harder (because that often involves diving into the change history).
  - uecker 3y ago
    I fully agree that this is the cardinal sin of C++. I think that C still offers much better encapsulation by using interfaces based on incomplete struct types. While I understand your point regarding inline, there are some comments I would like to make: It is now there and removing it would break existing code. The alternative are often macros, but inline functions where they can replace macros are better and the compiler can decide not to inline when it does not make sense. LTO is an alternative, but does not work across library boundaries, and also has a very substantial compile-time cost. Compiling with a new language mode does not force you to move variable declarations to the point of initialization, but you would now have the option to improve the code in this way when it makes sense. It is difficult to see this as an disadvantage. My point is that moving it to a new language version would usually not require changes to the code, except where the old modes were dangerous. So I would expect to find serious bugs when doing this.
    - flohofwoe 3y ago
      > ... So I would expect to find serious bugs when doing this. That's actually a good point hmmm (not in case of this specific assembler, which seems to be quite robust and well-written), and even if there would be serious memory corruption errors lurking, they would be contained because the assemblers runs in a WASM VM. For projects that are still maintained, a "moving standard" isn't that much of a problem, after all we've been conditioned that every new compiler update adds new warnings which "break" existing code ;) ...there is a certain value in taking a "finished/frozen" project and integrate that into a new project without requiring code changes though. I'm sure there must be a good middle-ground for C, where obviously bad and outdated language features (starting with leftovers from the K&R era) can be removed without causing too much breakage even on most old code ... but then, why keep 'inline' ;P
    - pjmlp 3y ago
      Which C++ fixed with modules. Something that most likely C will never have.
      - flohofwoe 3y ago

uecker 3y ago

What is wrong with "inline"? I do not think it is feasible to maintain all language versions in parallel for eternity. What would make porting this code to a newer standard difficult in this specific case?

flohofwoe 3y ago
Inline "encourages" moving implementation code into headers instead of only interface declarations, and the inline feature isn't all that useful anymore with LTO anyway. It's a good thing to only have declarations in headers, it simplifies parsing with 3rd party tools (to generate language bindings), and speeds up compilation (see the C++ stdlib headers for the canonical "why is implementation code in headers a bad idea" example). IMHO mixing interface declarations with implementation details was one of the cardinal sins of C++. > What would make porting this code to a newer standard difficult in this specific case? It's pointless busywork, and it's unclear how deep the changes should go (for instance: does it make sense to move C89 variable declaration from the start of scope blocks to their initialization point just because it might potentially be "safer" but touches half of all lines of code?). The code demonstrably works as C89, and any bugs that matter most likely had already been fixed decades ago, also doing large scale syntax changes is just noise in version control which makes bug fixing harder (because that often involves diving into the change history).
- uecker 3y ago
  I fully agree that this is the cardinal sin of C++. I think that C still offers much better encapsulation by using interfaces based on incomplete struct types. While I understand your point regarding inline, there are some comments I would like to make: It is now there and removing it would break existing code. The alternative are often macros, but inline functions where they can replace macros are better and the compiler can decide not to inline when it does not make sense. LTO is an alternative, but does not work across library boundaries, and also has a very substantial compile-time cost. Compiling with a new language mode does not force you to move variable declarations to the point of initialization, but you would now have the option to improve the code in this way when it makes sense. It is difficult to see this as an disadvantage. My point is that moving it to a new language version would usually not require changes to the code, except where the old modes were dangerous. So I would expect to find serious bugs when doing this.
  - flohofwoe 3y ago
    > ... So I would expect to find serious bugs when doing this. That's actually a good point hmmm (not in case of this specific assembler, which seems to be quite robust and well-written), and even if there would be serious memory corruption errors lurking, they would be contained because the assemblers runs in a WASM VM. For projects that are still maintained, a "moving standard" isn't that much of a problem, after all we've been conditioned that every new compiler update adds new warnings which "break" existing code ;) ...there is a certain value in taking a "finished/frozen" project and integrate that into a new project without requiring code changes though. I'm sure there must be a good middle-ground for C, where obviously bad and outdated language features (starting with leftovers from the K&R era) can be removed without causing too much breakage even on most old code ... but then, why keep 'inline' ;P
  - pjmlp 3y ago
    Which C++ fixed with modules. Something that most likely C will never have.
    - flohofwoe 3y ago