Implementing Go's defer keyword in C++

Re:Implementing Go's defer keyword in C++ by alexgartrell on Saturday October 21, 2017 @05:44PM (#15523778)

ScopeGuards as imagined here (Facebook's folly library has one) are near-essential for writing reasonable systems code in C++.

   int fd = socket(...);
   if (fd < 0) return false;
   SCOPE_EXIT { ::close(fd); };

   if (ioctl(fd, ...) != 0) return false;
   if (ioctl(fd, ...) != 0) return false;
   ...

   return true;

You could totally just write the FdWrapper class, but then you're still a user handling resource cleanup, but with more lines.

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Re:Implementing Go's defer keyword in C++ by bodyfour on Saturday October 21, 2017 @07:29PM (#15524188)

> You could totally just write the FdWrapper class

Yes, and that RAII class would be reusable all of the places you need to close a file descriptor. It's even a handy place to hang more methods that work on the descriptor... for instance if you wanted to abstract those ioctls.

That's why I personally never use ScopeGuards in C++. You are correct that writing a single-use RAII class requires a few lines of extra code. However I have found that after I write such a class I often find myself using it over and over.

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Re:Implementing Go's defer keyword in C++ by ot on Saturday October 21, 2017 @06:45PM (#15524025)

> You could totally just write the FdWrapper class

Which, BTW, is exactly what folly::File does :)

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