Comment by kazinator | Hacker News Reader

Comment by kazinator | Hacker News Reader

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Pascal strings are not inherently memory safe:

   cat_pascal_strings(pascalstr *uninited_memory,
                      pascalstr *left,
                      pascalstr *right);

how big is uninited_memory? Can left and right fit into it?

You need to design language constructs around Pascal srings to make them actually safe. Such as, oh, make it impossible to have an uninitialized such object. The object has o know both its allocation size and the actual size of the string stored in it.

What is unsafe is constructing new objects in an anonymous block of memory that knows nothing about its size.

C programs run aground there not just with strings!

   struct foo *ptr = malloc(sizeof ptr);  // should be sizeof *ptr!!

   if (ptr) {
      ptr->name = name;
      ptr->frobosity = fr;

Oops! The wrong size of allocated only the size of a pointer: 4 or 8 bytes, typically nowadays, but the structure is 48 bytes wide.

"struct foo" itself isn't inferior to a Pascal RECORD; the problem is coming from the wild and loose allocation side of things.

Working with strings in Pascal is relatively safe, but painfully limiting. It's a dead end. You can't build anything on top of it. Can you imagine trying to make a run-time for a high level language in Pascal? You need to be in the driver's seat regarding how strings work.

"Can you imagine trying to make a run-time for a high level language in Pascal"

You mean like the strings in Delphi? Yeah, I can since I use them daily. Strings in Delphi nowadays are actually more like classes in java than Old Pascal strings. Then depending on your intend either get them to be arrays or old strings after linker goes over your code. Best of both worlds, and on top of it, if you really want, you can definitely shoot yourself in your leg with unsafe operations. So in the end is best of both worlds and worse of 3rd world. Though the 3rd one you really need to go out of your way to have it as bad as C strings are.

> Working with strings in Pascal is relatively safe, but painfully limiting. It's a dead end. You can't build anything on top of it. Can you imagine trying to make a run-time for a high level language in Pascal? You need to be in the driver's seat regarding how strings work.

I doubt string representation is really the blocker here since C-strings are now pretty much just used by some but not all C programmers. QString and GString and C++ std::string and Rust strings and Go strings and Java strings and so on are not null terminated

I can totally imagine trying to make a run-time for a high-level language in any sensible Pascal dialect, such as Turbo/Borland Pascal. I mean, forget strings - that thing had syntax specifically to implement interrupt handlers, or access absolute memory addresses.

Better yet, how about Modula-2? I can't help but think that the programming language landscape would be much better if that language occupied the niche that C does today.

In the Pascal that I remember, strings were always 256 bytes and the first byte tracked the length, meaning they were always safe, though might get truncated. The LongString just did allocations whenever it needed, and was also safe, as long as you weren’t rolling your own pointer math.

> struct foo ptr = malloc(sizeof ptr); // should be sizeof ptr!!

This is why whenever I use sizeof, I pass a type, not a variable.

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