3 ms·

> And I won't get started with C strings, which are just a historical BadIdea™. What's the better alternative to null-prefixed strings you are referring to, le

> And I won't get started with C strings, which are just a historical BadIdea™. What's the better alternative to null-prefixed strings you are referring to, length prefixed?

dr_zoidberg 5y ago
Those would be Pascal Strings (length at the start, then the bytes). Those make for very easy to write code, but they come with a few issues, but in general they are simpler and give better behavior than null-terminated strings. However, as for a bit of a historical bagagge, it seems we got used to null-terminated strings and just went on with them.
- pjmlp 5y ago
  Only in C, even C++ has since the early days adopted proper strings on its standard library, initially the compiler specific ones from the early 90's, then the standard one.
  - dr_zoidberg 5y ago
    Sure, its just that these kind of strings were historically called Pascal-strings [0] because they were the way Pascal implemented strings. [0] And still are! For example, Python refers to them as such, see the "p" (lowercase p) character code here: https://docs.python.org/3/library/struct.html#format-strings https://docs.python.org/3/library/struct.html#format-strings
    - pjmlp 5y ago
      Not all C++ string libraries use Pascal strings. Some of them use a fat pointer instead, with a mix of counter, pointer to the end, and null terminator for C compatibility.
      - dr_zoidberg 5y ago
        That's ingenious, but I don't think I've heard a name for those kind of strings.
        pjmlp 5y ago
        One thing is certain, they aren't Pascal strings.
qalmakka 5y ago
Null terminated strings are the root cause of millions, if not billions of security vulnerabilities caused by buffer overflows. All modern languages have shunned null-terminated strings in favour of something in the likes of struct string_type { char *ptr; // or char[] size_t size; } because the whole idea of scrolling a whole string just to get its length it's an immense waste of CPU time. It has been optimized to death given that C does that for historical reasons¹, but still it's unwieldy and less safe. For instance, C strings make 0-cost string slicing impossibile: for instance, if you wanted to slice a string to get str[2;4] (i.e. a 2 char string from position 2), it would be simply string slice { .data = str.data + 2, .size = 2 } with the C++/Java/Rust/whatever approach. With C strings, given that you have to put a '\0' terminator at string end, you're forced to allocate memory and memcpy() the string, or to corrupt the original string. ¹: size_t is much bigger than char (2x on 16 bit, 8x on 64 bit machines), so it made sense on a memory constrained machine like the PDP-11 to waste CPU time in order to save memory.

> And I won't get started with C strings, which are just a historical BadIdea™. What's the better alternative to null-prefixed strings you are referring to, length prefixed?

dr_zoidberg 5y ago

Those would be Pascal Strings (length at the start, then the bytes). Those make for very easy to write code, but they come with a few issues, but in general they are simpler and give better behavior than null-terminated strings. However, as for a bit of a historical bagagge, it seems we got used to null-terminated strings and just went on with them.

pjmlp 5y ago
Only in C, even C++ has since the early days adopted proper strings on its standard library, initially the compiler specific ones from the early 90's, then the standard one.
- dr_zoidberg 5y ago
  Sure, its just that these kind of strings were historically called Pascal-strings [0] because they were the way Pascal implemented strings. [0] And still are! For example, Python refers to them as such, see the "p" (lowercase p) character code here: https://docs.python.org/3/library/struct.html#format-strings https://docs.python.org/3/library/struct.html#format-strings
  - pjmlp 5y ago
    Not all C++ string libraries use Pascal strings. Some of them use a fat pointer instead, with a mix of counter, pointer to the end, and null terminator for C compatibility.
    - dr_zoidberg 5y ago
      That's ingenious, but I don't think I've heard a name for those kind of strings.
      - pjmlp 5y ago
        One thing is certain, they aren't Pascal strings.

qalmakka 5y ago

Null terminated strings are the root cause of millions, if not billions of security vulnerabilities caused by buffer overflows. All modern languages have shunned null-terminated strings in favour of something in the likes of struct string_type { char *ptr; // or char[] size_t size; } because the whole idea of scrolling a whole string just to get its length it's an immense waste of CPU time. It has been optimized to death given that C does that for historical reasons¹, but still it's unwieldy and less safe. For instance, C strings make 0-cost string slicing impossibile: for instance, if you wanted to slice a string to get str[2;4] (i.e. a 2 char string from position 2), it would be simply string slice { .data = str.data + 2, .size = 2 } with the C++/Java/Rust/whatever approach. With C strings, given that you have to put a '\0' terminator at string end, you're forced to allocate memory and memcpy() the string, or to corrupt the original string. ¹: size_t is much bigger than char (2x on 16 bit, 8x on 64 bit machines), so it made sense on a memory constrained machine like the PDP-11 to waste CPU time in order to save memory.