Lambdas, Nested Functions, and Blocks (2021)

3 comments

• PaulHoule 12 hours ago
  I always thought that if you wanted variables to be able to escape the function they were defined in you have to allocate them on the heap and then you need some kind of garbage collection.
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  • ori_b 11 hours ago
    You can also have some kind of heapify/free, with undefined behavior if you get it wrong.

    I think the C standards committee needs to figure out memory safety before adding any new features that are likely to interact with it.

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    • PaulHoule 9 hours ago
      So you're saying the runtime mallocs the pointer to the closure and it's your responsibility to free it when you don't need it anymore?
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      • ori_b 8 hours ago
        Kinda. Here's an example:

             void
             mkclosure(int x)
             {
                 int x;
                 void fn(void){ return x + 1; }
                 return fnheapify(fn);
             }
        
             void
             useclosure(void)
             {
                 void (^fn)(void) = mkclosure(42);
                 fn();
                 fnfree(fn);
             }
• remexre 12 hours ago
  Are there any implementations of this lambdas proposal on top of any production-quality compilers? Or are there some updates on how this is doing in committee?
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  • uecker 1 hour ago
    I recently wrote some paper: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n3654.pdf which also includes a short summary of issues when trying to put C++'s lambdas into C.
  • mwkaufma 5 hours ago
    It's straight from C++ which has had them since 2011.
• mwkaufma 5 hours ago
  "Unfortunately, many compiler authors would absolutely give our recommended advice a gigantic middle finger."

  Simmer down, now.