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Giving C a superpower: custom header file (safe_c.h)

(hwisnu.bearblog.dev)
271 points mithcs | 1 comments | 17 Nov 25 10:40 UTC | HN request time: 0.001s | source
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woodruffw ◴[17 Nov 25 13:30 UTC] No.45953391[source]▶
Intentionally or not, this post demonstrates one of the things that makes safer abstractions in C less desirable: the shared pointer implementation uses a POSIX mutex, which means it’s (1) not cross platform, and (2) pays the mutex overhead even in provably single-threaded contexts. In other words, it’s not a zero-cost abstraction.

C++’s shared pointer has the same problem; Rust avoids it by having two types (Rc and Arc) that the developer can select from (and which the compiler will prevent you from using unsafely).

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1. lelanthran ◴[17 Nov 25 16:14 UTC] No.45954940[source]▶
> Intentionally or not, this post demonstrates one of the things that makes safer abstractions in C less desirable: the shared pointer implementation uses a POSIX mutex, which means it’s (1) not cross platform, and (2) pays the mutex overhead even in provably single-threaded contexts. In other words, it’s not a zero-cost abstraction.

It's an implementation detail. They could have used atomic load/store (since c11) to implement the increment/decrement.

TBH I'm not sure what a mutex buys you in this situation (reference counting)