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

(hwisnu.bearblog.dev)
271 points mithcs | 2 comments | 17 Nov 25 10:40 UTC | HN request time: 0.399s | 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. kev009 ◴[17 Nov 25 17:13 UTC] No.45955631[source]▶
C11 has a mutex API (threads.h), so why would it rely on POSIX? Are you sure it's not an runtime detail on one platform? https://devblogs.microsoft.com/cppblog/c11-threads-in-visual...
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2. loeg ◴[17 Nov 25 22:34 UTC] No.45959191[source]▶
The article has an excerpt using posix mutexes specifically. But you're right that C11 code can just portably use standard mutexes.

  // The old way of manual reference counting
  typedef struct {
      MatchStore* store;
      int ref_count;
      pthread_mutex_t mutex;
  } SharedStore;