Replies

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  James WidmanJamesWidman@mastodon.social

  Jan 15, 2025, 1:18 AM

  @joe @thephd @euneuber more seriously: i can't seem to find it in the video now, but i think there is actually a proposed rule for _Operator() that's says that an operand type cannot be a pointer type..? (so iiuc, the compiler would error on your _Operator(<<) above).

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  James WidmanJamesWidman@mastodon.social

  Jan 15, 2025, 1:24 AM

  @joe @thephd @euneuber ...But i think it might allow:

  _Operator(>>, &, const char, FILE, fputs);

  (the function signature is fputs(const char*, FILE*);)

  ...i think...? And that means that:

  const char *s = "hello";
  FILE *f = fopen(/*...*/);

  *s >> *f;

  would translate to:

  fputs(&*s, &*f);

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  James WidmanJamesWidman@mastodon.social

  Jan 15, 2025, 1:53 AM

  @joe @thephd @euneuber found the relevant bit in the video, starting at about 58:00, in response to a question about pointers:

  [58:45] "[...] the same way you can't override for `int, int`, you can't override it for `int *` or `MyStruct * [...] [A pointer is] still a built-in type, even though it's a pointer to your type."

  So, a compiler would issue an error for:
  _Operator(<<, FILE*, const char *, fputs);

  ...because both operand types are built-in types...

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  James WidmanJamesWidman@mastodon.social

  Jan 15, 2025, 1:55 AM

  @joe @thephd @euneuber but:

  _Operator(>>, &, const char, FILE, fputs);

  ... would be allowed because FILE is a struct type and not a pointer type.

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  James WidmanJamesWidman@mastodon.social

  Jan 15, 2025, 1:56 AM

  @joe @thephd @euneuber [cue the introduction of operators for string-slice types]

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  Björkus "No time_t to Die" Dorkusthephd@pony.social

  Jan 15, 2025, 3:52 PM

  @JamesWidman @joe @euneuber FILE is not required to be a complete type, so that code might not work everywhere.

  It also would only work if you gave it a dereferenced char at the start of the array, not any old pointer.

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  James WidmanJamesWidman@mastodon.social

  Jan 15, 2025, 4:53 PM

  @thephd @joe @euneuber TIL that the definition of "lvalue" was modified to "an expression with [...] a complete object type" sometime after C99 (in which the definition didn't mention completeness), thus rendering expressions like &*p ill-formed when typeof(*p) is incomplete

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