3 ms·

I'm in the WG14 and my opinion is that there isn't one good way to do strings it all depends on what you value (performance/ memory use) and the usage pattern.

I'm in the WG14 and my opinion is that there isn't one good way to do strings it all depends on what you value (performance/ memory use) and the usage pattern. C in general only deal with data types, north their semantic meaning. (IOW We say what a float is not what it is used for). The two main deviations from that are text and time and both of them are causing us a lot of issues. My opinion is that writing your own text code is the best solution and the most "C" solution. Te one proposal i have heard that i like is for C to get versions of functions that use strings that take an array and a length, so as to not force the convention of null termination in order to use things like fopen.

hgs3 4y ago
Has WG14 considered adding slices to C? [1] Introducing slices would naturally give way to a better string library. [1] https://www.digitalmars.com/articles/C-biggest-mistake.html https://www.digitalmars.com/articles/C-biggest-mistake.html
- quelsolaar 4y ago
  Its been 50 years so pretty much everything has been considered. In my opinion the mistake was not having arrays decay in to pointers but rather arrays should be pointers in the first place. An array should be seen as a number of values where with a pointer pointing at the first one. I think adding a third version of the same functionality would just complicate things further. (&p[42] is a "slice" of an array) Another thing I do not like about slices that store lengths, is that they hide memory layout from the user and that is not a very C thing to do.
  - uecker 4y ago
    If you think about arrays as pointers, you will get a lot of things wrong, e.g. float m[10][10]; it not a an array of pointers, but a 2D dimensional array with 2D memory layout.
    - quelsolaar 4y ago
      You are right, sizeof is the other big difference. I think these differences are small enough that it was a mistake separate the two. The similarities / differences do make them confusing.
      - uecker 4y ago
        How would you express a 2D memory layout with only pointers?
        colejohnson66 4y ago
        An array of pointers to arrays? Basically, a `T**` C#'s "jagged" arrays are like this, and to get a "true" 2D array, you use different syntax (a comma in the indexer): int[][] jagged; // an array of `int[]` (i.e. each element is a pointer to a `int[]`) int[,] multidimensional; // a "true" 2D array laid out in memory sequentially // allocate the jagged array; each `int[]` will be null until allocated separately jagged = new int[][10]; Debug.Assert(jagged.All(elem => elem == null)); for (int i = 0; i < 10; i++) jagged[i] = new double[10]; // allocate the internal arrays Debug.Assert(jagged[i][j] == 0); // allocate the multidimensional array; each `int` will be `default` which is 0 // element [i,j] will be at offset `10*i + j` multiDimensional = new double[10, 10]; Debug.Assert(multiDimensional[i, j] == 0);
        uecker 4y ago
        Yes, this is people with pre-C99 compilers that do not support variably modified types sometimes do. It is horrible (although there are some use cases).
- uecker 4y ago
  I plan to bring such a proposal forward for the next version. Note that C already has everything to do this without much overhead, e.g. in C23 you can write: int N = 10; char buf[N] = { }; auto x = &buf; and 'x' has a slice type that automatically remebers the size. This works today with GCC / clang (with extensions or C2X language mode: https://godbolt.org/z/cMbM57r46 https://godbolt.org/z/cMbM57r46 ). We simply can not name it without referring to N and we can also not use it in structs (ouch).
  - quelsolaar 4y ago
    You know what i think about auto :-) How is this not a quality of implementation issue? Any implementation is free to track all sizes as much as they want with the current standard. Either a implementation is forced to issue an error at run time if there is an out of bounds read/write and in that case its a very different language than C, or its feature as-if lets any implementation ignore.
    - uecker 4y ago
      Tracking sizes for purposes of bounds checking is QoI and I think this is perfectly fine. But here we can also recover the size with sizeof, so it is also required for compliance: https://godbolt.org/z/qh7P93Tcd https://godbolt.org/z/qh7P93Tcd And I agree that this is a misuse of auto. I only used it here to show that the type we miss already exists inside the C compiler, we simply can name it only by constructing it again: char (buf)[N] = ... but we could simply allow char (buf)[:] = and be done (as suggested by Dennis Richtie: https://www.bell-labs.com/usr/dmr/www/vararray.pdf https://www.bell-labs.com/usr/dmr/www/vararray.pdf)

hgs3 4y ago

Has WG14 considered adding slices to C? [1] Introducing slices would naturally give way to a better string library. [1] https://www.digitalmars.com/articles/C-biggest-mistake.html https://www.digitalmars.com/articles/C-biggest-mistake.html

quelsolaar 4y ago
Its been 50 years so pretty much everything has been considered. In my opinion the mistake was not having arrays decay in to pointers but rather arrays should be pointers in the first place. An array should be seen as a number of values where with a pointer pointing at the first one. I think adding a third version of the same functionality would just complicate things further. (&p[42] is a "slice" of an array) Another thing I do not like about slices that store lengths, is that they hide memory layout from the user and that is not a very C thing to do.
- uecker 4y ago
  If you think about arrays as pointers, you will get a lot of things wrong, e.g. float m[10][10]; it not a an array of pointers, but a 2D dimensional array with 2D memory layout.
  - quelsolaar 4y ago
    You are right, sizeof is the other big difference. I think these differences are small enough that it was a mistake separate the two. The similarities / differences do make them confusing.
    - uecker 4y ago
      How would you express a 2D memory layout with only pointers?
      - colejohnson66 4y ago
        An array of pointers to arrays? Basically, a `T**` C#'s "jagged" arrays are like this, and to get a "true" 2D array, you use different syntax (a comma in the indexer): int[][] jagged; // an array of `int[]` (i.e. each element is a pointer to a `int[]`) int[,] multidimensional; // a "true" 2D array laid out in memory sequentially // allocate the jagged array; each `int[]` will be null until allocated separately jagged = new int[][10]; Debug.Assert(jagged.All(elem => elem == null)); for (int i = 0; i < 10; i++) jagged[i] = new double[10]; // allocate the internal arrays Debug.Assert(jagged[i][j] == 0); // allocate the multidimensional array; each `int` will be `default` which is 0 // element [i,j] will be at offset `10*i + j` multiDimensional = new double[10, 10]; Debug.Assert(multiDimensional[i, j] == 0);
        uecker 4y ago
        Yes, this is people with pre-C99 compilers that do not support variably modified types sometimes do. It is horrible (although there are some use cases).
uecker 4y ago
I plan to bring such a proposal forward for the next version. Note that C already has everything to do this without much overhead, e.g. in C23 you can write: int N = 10; char buf[N] = { }; auto x = &buf; and 'x' has a slice type that automatically remebers the size. This works today with GCC / clang (with extensions or C2X language mode: https://godbolt.org/z/cMbM57r46 https://godbolt.org/z/cMbM57r46 ). We simply can not name it without referring to N and we can also not use it in structs (ouch).
- quelsolaar 4y ago
  You know what i think about auto :-) How is this not a quality of implementation issue? Any implementation is free to track all sizes as much as they want with the current standard. Either a implementation is forced to issue an error at run time if there is an out of bounds read/write and in that case its a very different language than C, or its feature as-if lets any implementation ignore.
  - uecker 4y ago
    Tracking sizes for purposes of bounds checking is QoI and I think this is perfectly fine. But here we can also recover the size with sizeof, so it is also required for compliance: https://godbolt.org/z/qh7P93Tcd https://godbolt.org/z/qh7P93Tcd And I agree that this is a misuse of auto. I only used it here to show that the type we miss already exists inside the C compiler, we simply can name it only by constructing it again: char (buf)[N] = ... but we could simply allow char (buf)[:] = and be done (as suggested by Dennis Richtie: https://www.bell-labs.com/usr/dmr/www/vararray.pdf https://www.bell-labs.com/usr/dmr/www/vararray.pdf)