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Of all the nails that could be used to seal Pascal’s coffin, the one I use is that I can’t write ‘writeln’ in Pascal. Other than that, it was great in it’s tim

Of all the nails that could be used to seal Pascal’s coffin, the one I use is that I can’t write ‘writeln’ in Pascal. Other than that, it was great in it’s time (mid 70’s for me).

pjmlp 7y ago
How do you write malloc() and exit() in C? You don't, it has to be in Assembly or calling underlying OS APIs. So also a nail in C's coffin.
- danmg 7y ago
  malloc: Have a big static block of uint8_t and return pointers from it. exit: longjmp.
  - nybble41 7y ago
    > malloc: Have a big static block of uint8_t and return pointers from it. According to C99 section 6.5 paragraphs 6-7 that would be undefined behavior. The declared type of the object is uint8_t and you're accessing it through an lvalue expression which is not compatible with uint8_t. (You can access any object through a character-type lvalue, but the reverse is not true.) The malloc() function is required to return memory which is disjoint from any other object—that includes your uint8_t array. Besides aliasing concerns, your character array may not be properly aligned for whatever type is being stored there and there is no way within the C99 standard to determine the alignment of the array or the required alignment for the stored type. > exit: longjmp. That might work, in a single-threaded program, if you longjmp() back to main() and return. There's no telling what might happen if you did that from another thread, of course, but then C99 doesn't really cover threads.
    - danmg 7y ago
      Put the block in a struct and use allignment keywords.
      - nybble41 7y ago
        If you're lucky enough to be using C11 or C18, sure. There are no alignment keywords in C99. However, that still leaves the aliasing issue, and the fact that objects allocated with malloc() are defined not to overlap with any other object.
        danmg 7y ago
        well you also need another static block for the allocation bitmap or whatever structure you're going to use. How would the pointers that you're generated be aliased if they're unique according to your free map.
        nybble41 7y ago
        They're aliased with the array that you allocated them from. The compiler is free to assume that elements in an array with a declared type of uint8_t won't be accessed via any other type of lvalue (other than another character type). Doing so is undefined behavior, which means there are no guarantees about how any part of the program behaves before or after such an access. In many cases you can get away with it, of course, but a strictly conforming C program can't rely on that.
  - pjmlp 7y ago
    Funny, malloc() implemented that way is UB and doesn't work in all cases, specially when passing pointers around dynamic loaded libraries or threads. So exit() gets to call longjmp() which definitely can only be done in Assembly, back to step 1.
    - danmg 7y ago
      Isn't this how malloc was done on classic MacOS?
      - pjmlp 7y ago
        Classic MacOS was written in a mix of Assembly and Apple Pascal. C was a guest language via MPW, and plugged into those APIs.
SideburnsOfDoom 7y ago
Things such as "implement the 'writeln' function" fall under the umbrella of "operating system interop" or "Foreign function interface", don't they? Any general-purpose programming language, pascal or not, will eventually have that. But it might not be in a general language standard.
- ken 7y ago
  I think the point is that it’s not so rare that one might run into this type of situation. The article even mentions one. > It is unfortunate that there is no way to make this convenience available to routines in general.
clouddrover 7y ago
> I can’t write ‘writeln’ in Pascal Let's not talk about Pascal from over 40 years ago, let's talk about today's Pascal. Why can't you write "writeln" in today's Pascal?
- ken 7y ago
  According to Rosetta Code [1], “Standard Pascal does not allow variadic functions” — though specific implementations have proprietary extensions which allow this. [1]: https://rosettacode.org/wiki/Variadic_function#Pascal https://rosettacode.org/wiki/Variadic_function#Pascal
  - clouddrover 7y ago
    Which compiler are you going to use for "standard pascal"? The Pascal compilers you're going to use in practice are either Free Pascal or Delphi. They are what Pascal is today: https://rosettacode.org/wiki/Variadic_function#Free_Pascal https://rosettacode.org/wiki/Variadic_function#Free_Pascal
  - unnouinceput 7y ago
    None uses that "standard" when writing stuff in Pascal. Real world uses either Delphi or Lazarus+FreePascal. Both of them have Writeln and variadic functions
    - e12e 7y ago
      Note, I think the point wasn't that Pascal didn't have writeln, rather that you couldn't write (implement) writeln in Pascal (presumably due to missing variadic functions). So having writeln isn't really the issue, the issue is that writeln is magic/a built-in. Is free pascal self hosted?
      - clouddrover 7y ago
        > Is free pascal self hosted? Yes.
      - 7y ago
Akira1364 7y ago
You use "array of const" to write the equivalent of a regular C variadic function in modern Pascal implementations such as Delphi and Free Pascal: https://www.freepascal.org/docs-html/ref/refsu69.html https://www.freepascal.org/docs-html/ref/refsu69.html That said, as far as at least Free Pascal goes, there isn't actually even a specific function called `writeln` with a real body that you can go and look at somewhere. It's a magic language-level intrinsic that gets broken down into calls to various other intrinsics by the compiler based on what's passed to it.

Of all the nails that could be used to seal Pascal’s coffin, the one I use is that I can’t write ‘writeln’ in Pascal. Other than that, it was great in it’s time (mid 70’s for me).

pjmlp 7y ago

How do you write malloc() and exit() in C? You don't, it has to be in Assembly or calling underlying OS APIs. So also a nail in C's coffin.

danmg 7y ago
malloc: Have a big static block of uint8_t and return pointers from it. exit: longjmp.
- nybble41 7y ago
  > malloc: Have a big static block of uint8_t and return pointers from it. According to C99 section 6.5 paragraphs 6-7 that would be undefined behavior. The declared type of the object is uint8_t and you're accessing it through an lvalue expression which is not compatible with uint8_t. (You can access any object through a character-type lvalue, but the reverse is not true.) The malloc() function is required to return memory which is disjoint from any other object—that includes your uint8_t array. Besides aliasing concerns, your character array may not be properly aligned for whatever type is being stored there and there is no way within the C99 standard to determine the alignment of the array or the required alignment for the stored type. > exit: longjmp. That might work, in a single-threaded program, if you longjmp() back to main() and return. There's no telling what might happen if you did that from another thread, of course, but then C99 doesn't really cover threads.
  - danmg 7y ago
    Put the block in a struct and use allignment keywords.
    - nybble41 7y ago
      If you're lucky enough to be using C11 or C18, sure. There are no alignment keywords in C99. However, that still leaves the aliasing issue, and the fact that objects allocated with malloc() are defined not to overlap with any other object.
      - danmg 7y ago
        well you also need another static block for the allocation bitmap or whatever structure you're going to use. How would the pointers that you're generated be aliased if they're unique according to your free map.
        nybble41 7y ago
        They're aliased with the array that you allocated them from. The compiler is free to assume that elements in an array with a declared type of uint8_t won't be accessed via any other type of lvalue (other than another character type). Doing so is undefined behavior, which means there are no guarantees about how any part of the program behaves before or after such an access. In many cases you can get away with it, of course, but a strictly conforming C program can't rely on that.
- pjmlp 7y ago
  Funny, malloc() implemented that way is UB and doesn't work in all cases, specially when passing pointers around dynamic loaded libraries or threads. So exit() gets to call longjmp() which definitely can only be done in Assembly, back to step 1.
  - danmg 7y ago
    Isn't this how malloc was done on classic MacOS?
    - pjmlp 7y ago
      Classic MacOS was written in a mix of Assembly and Apple Pascal. C was a guest language via MPW, and plugged into those APIs.

SideburnsOfDoom 7y ago

Things such as "implement the 'writeln' function" fall under the umbrella of "operating system interop" or "Foreign function interface", don't they? Any general-purpose programming language, pascal or not, will eventually have that. But it might not be in a general language standard.

ken 7y ago
I think the point is that it’s not so rare that one might run into this type of situation. The article even mentions one. > It is unfortunate that there is no way to make this convenience available to routines in general.

clouddrover 7y ago

> I can’t write ‘writeln’ in Pascal Let's not talk about Pascal from over 40 years ago, let's talk about today's Pascal. Why can't you write "writeln" in today's Pascal?

ken 7y ago
According to Rosetta Code [1], “Standard Pascal does not allow variadic functions” — though specific implementations have proprietary extensions which allow this. [1]: https://rosettacode.org/wiki/Variadic_function#Pascal https://rosettacode.org/wiki/Variadic_function#Pascal
- clouddrover 7y ago
  Which compiler are you going to use for "standard pascal"? The Pascal compilers you're going to use in practice are either Free Pascal or Delphi. They are what Pascal is today: https://rosettacode.org/wiki/Variadic_function#Free_Pascal https://rosettacode.org/wiki/Variadic_function#Free_Pascal
- unnouinceput 7y ago
  None uses that "standard" when writing stuff in Pascal. Real world uses either Delphi or Lazarus+FreePascal. Both of them have Writeln and variadic functions
  - e12e 7y ago
    Note, I think the point wasn't that Pascal didn't have writeln, rather that you couldn't write (implement) writeln in Pascal (presumably due to missing variadic functions). So having writeln isn't really the issue, the issue is that writeln is magic/a built-in. Is free pascal self hosted?
    - clouddrover 7y ago
      > Is free pascal self hosted? Yes.
    - 7y ago

Akira1364 7y ago

You use "array of const" to write the equivalent of a regular C variadic function in modern Pascal implementations such as Delphi and Free Pascal: https://www.freepascal.org/docs-html/ref/refsu69.html https://www.freepascal.org/docs-html/ref/refsu69.html That said, as far as at least Free Pascal goes, there isn't actually even a specific function called `writeln` with a real body that you can go and look at somewhere. It's a magic language-level intrinsic that gets broken down into calls to various other intrinsics by the compiler based on what's passed to it.