static void notify_using()

in src/pal/pal_apple.h [162:205]

• 30 lines of code
• 8 McCabe index (conditional complexity)

    static void notify_using(void* p, size_t size) noexcept
    {
      KeepErrno e;
      SNMALLOC_ASSERT(
        is_aligned_block<page_size>(p, size) || (zero_mem == NoZero));

      if constexpr (zero_mem == YesZero)
      {
        void* r = mmap(
          p,
          size,
          PROT_READ | PROT_WRITE,
          MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED,
          anonymous_memory_fd,
          0);

        if (SNMALLOC_LIKELY(r != MAP_FAILED))
        {
          return;
        }
      }

      if constexpr (PalEnforceAccess)
      {
        // Mark pages as writable for `madvise` below.
        //
        // `mach_vm_protect` is observably slower in benchmarks.
        mprotect(p, size, PROT_READ | PROT_WRITE);
      }

      // `MADV_FREE_REUSE` can only be applied to writable pages,
      // otherwise it's an error.
      //
      // `mach_vm_behavior_set` is observably slower in benchmarks.
      //
      // macOS 11 Big Sur may behave in an undocumented manner.
      while (madvise(p, size, MADV_FREE_REUSE) == -1 && errno == EAGAIN)
        ;

      if constexpr (zero_mem == YesZero)
      {
        ::bzero(p, size);
      }
    }