6 ms·

thanks man! yes that makes sense. unfortunately 30cc is not able to compile that syntax, and will probably give type-checker errors when passing a void* to poi

thanks man! yes that makes sense. unfortunately 30cc is not able to compile that syntax, and will probably give type-checker errors when passing a void* to pointer of another type. but will implement it sometime soon!

unwind 2y ago
Aha, so it doesn't know about void* being compatible with all (object) pointers, but so far just requires the pointers to match exactly? I see. Not sure why I was down-voted, I think that is ... not nice. :(
- nar001 2y ago
  I don't think you can be downvoted, there's no downvote button
  - hollerith 2y ago
    Users with enough karma can downvote comments.
  - quuxplusone 2y ago
    A beautiful example of Cunningham's Law! :)
- dataflow 2y ago
  I downvoted just because I thought it wasn't great advice. It makes the code incompatible with C++ compilers, and being able to compile C with C++ compiler is often useful. Also... it felt kind of... unnecessary? to tell someone who is making a compiler how to write basic code in the language they're writing a compiler for. It almost felt like telling an overweight medical student/doctor that he should avoid eating fatty foods.
  - Gibbon1 2y ago
    Writing C code so won't compile with a C++ compiler is gods work. Because C++ is why C can't have nice things.
KerrAvon 2y ago
I disagree with that advice, FWIW -- (void *) is the cause of a lot of bugs in C programs, and much stricter type checking was often the norm for compilers like CodeWarrior on platforms like classic Mac OS, where (a) if you got something wrong you'd corrupt app memory at best and the filesystem at worst and (b) many developers were used to Pascal, which was stricter. (Moving to GCC on Mac OS X and unexpectedly getting much more lenient type checking was a big surprise.)
- munch117 2y ago
  But adding the cast doesn't make type checking stricter, quite the opposite - it destroys any hope of the compiler checking the assignment. C++ shot itself in the foot by removing automatic conversion from void* to T*, because it forces programmers to add casts that weaken type safety.
- cataphract 2y ago
  It doesn't make it any safer because the cast is unchecked. It could be argued it's discouraged[1] for a reason that doesn't really apply to modern C versions where implicit-int isn't allowed anymore. But while the cast is a matter of style (or C++ compatibility), sizeof(*ret) is definitely superior to sizeof(thing_t). The reason is that people sometimes change the type of ret but forget the change the size of the allocation, especially if ret is assigned to on a different line it's declared. [1]: https://c-faq.com/malloc/mallocnocast.html https://c-faq.com/malloc/mallocnocast.html
KerrAvon 2y ago
If you're implementing C23 compatibility, you could do auto p = (thing_t *)malloc(sizeof(thing_t)); and you get both DRY and avoid (void *) casting.
- dcuthbertson 2y ago
  > and you get both DRY and avoid (void *) casting. While that line of code is DRY, it doesn't avoid casting "void *" to "thing_t *".

unwind 2y ago

Aha, so it doesn't know about void* being compatible with all (object) pointers, but so far just requires the pointers to match exactly? I see. Not sure why I was down-voted, I think that is ... not nice. :(

nar001 2y ago
I don't think you can be downvoted, there's no downvote button
- hollerith 2y ago
  Users with enough karma can downvote comments.
- quuxplusone 2y ago
  A beautiful example of Cunningham's Law! :)
dataflow 2y ago
I downvoted just because I thought it wasn't great advice. It makes the code incompatible with C++ compilers, and being able to compile C with C++ compiler is often useful. Also... it felt kind of... unnecessary? to tell someone who is making a compiler how to write basic code in the language they're writing a compiler for. It almost felt like telling an overweight medical student/doctor that he should avoid eating fatty foods.
- Gibbon1 2y ago
  Writing C code so won't compile with a C++ compiler is gods work. Because C++ is why C can't have nice things.

KerrAvon 2y ago

I disagree with that advice, FWIW -- (void *) is the cause of a lot of bugs in C programs, and much stricter type checking was often the norm for compilers like CodeWarrior on platforms like classic Mac OS, where (a) if you got something wrong you'd corrupt app memory at best and the filesystem at worst and (b) many developers were used to Pascal, which was stricter. (Moving to GCC on Mac OS X and unexpectedly getting much more lenient type checking was a big surprise.)

munch117 2y ago
But adding the cast doesn't make type checking stricter, quite the opposite - it destroys any hope of the compiler checking the assignment. C++ shot itself in the foot by removing automatic conversion from void* to T*, because it forces programmers to add casts that weaken type safety.
cataphract 2y ago
It doesn't make it any safer because the cast is unchecked. It could be argued it's discouraged[1] for a reason that doesn't really apply to modern C versions where implicit-int isn't allowed anymore. But while the cast is a matter of style (or C++ compatibility), sizeof(*ret) is definitely superior to sizeof(thing_t). The reason is that people sometimes change the type of ret but forget the change the size of the allocation, especially if ret is assigned to on a different line it's declared. [1]: https://c-faq.com/malloc/mallocnocast.html https://c-faq.com/malloc/mallocnocast.html

KerrAvon 2y ago

If you're implementing C23 compatibility, you could do auto p = (thing_t *)malloc(sizeof(thing_t)); and you get both DRY and avoid (void *) casting.

dcuthbertson 2y ago
> and you get both DRY and avoid (void *) casting. While that line of code is DRY, it doesn't avoid casting "void *" to "thing_t *".