digitalmars.D.bugs - [Issue 23919] New: cast array to pointer should be illegal
- d-bugmail puremagic.com (39/39) May 12 2023 https://issues.dlang.org/show_bug.cgi?id=23919
https://issues.dlang.org/show_bug.cgi?id=23919 Issue ID: 23919 Summary: cast array to pointer should be illegal Product: D Version: D2 Hardware: All OS: All Status: NEW Severity: enhancement Priority: P1 Component: dmd Assignee: nobody puremagic.com Reporter: schveiguy gmail.com Casting an array to a pointer is allowed: ```d import core.stdc.stdio; auto str = "hello"; printf(cast(char *)str[0 .. 3]); ``` This prints "hello". The user might think they have properly matched the requirements, but in actuality, all they have done is accessed the pointer. A few reasons why this is bad: 1. It's trivial (and more readable) to use `.ptr` instead of the cast 2. The cast must match the attributes or risk causing problems when code evolves. Casting is a blunt instrument, and should be discouraged when better alternatives exist. 3. The cast gives a false impression that something is happening underneath to ensure the data is correct. Many C functions require pointers instead of arrays, and this "seems" like the right answer. I think we should deprecate this "feature". I'm not exactly sure why this was needed in the first place. hopefully reconsider the decision. FWIW, the D discord has had a few people coming to ask why their code doesn't work when casting a `string` to a `char *`. I would pair such a cast error with a suggestion to use `toStringz` in the case of string to char * conversions. --
May 12 2023