3 ms·

Well, in C you very rarely need it, but in assembler (particularly the 8-bit Z80 and 6502 that I've written raft-loads of code for) you definitely do. Of cours

• formerly_proven 5y ago
  goto is the idiomatic way to emulate RAII in C. It's everywhere.
  • zabzonk 5y ago
    Please explain a little more with an example. Certainly not in my C code, though I a huge fan of RAII in C++.
    • panax 5y ago
      Here is an example with RAII and goto: https://wiki.sei.cmu.edu/confluence/display/c/MEM12-C.+Consider+using+a+goto+chain+when+leaving+a+function+on+error+when+using+and+releasing+resources https://wiki.sei.cmu.edu/confluence/display/c/MEM12-C.+Consi... Btw that is a Cert C recommendation to use goto for RAII! Take a look at the Linux kernel sometime, goto is everywhere there too https://www.kernel.org/doc/html/v4.10/process/coding-style.html#centralized-exiting-of-functions https://www.kernel.org/doc/html/v4.10/process/coding-style.h...
      • zabzonk 5y ago
        Not many of us are kernel developers, or agree whole-heartedly with their practices.
    • ahartmetz 5y ago
      A function that allocates resources in several steps jumps, on error, to the teardown part at the end to deallocate (in reverse order of allocation) only the resources that were allocated. The others are skipped (jumped over). It's very popular in the Linux kernel.
      • zabzonk 5y ago
        > only the resources that were allocated How does it know which were allocated and which were not? If you are talking about memory allocation, then you could simply deallocate all the pointers provided they were initially set to NULL. Freeing a NULL pointer is well-defined in C.
        • maccard 5y ago
          Files, sockets, mutexes are all examples of resources that aren't memory. Someone posted an example in this comment thread - [0]. [0] https://wiki.sei.cmu.edu/confluence/display/c/MEM12-C.+Consider+using+a+goto+chain+when+leaving+a+function+on+error+when+using+and+releasing+resources https://wiki.sei.cmu.edu/confluence/display/c/MEM12-C.+Consi...
          • zabzonk 5y ago
            > Files, sockets, mutexes are all examples of resources that aren't memory I know - that's why I explicitly mentioned memory.
        • ahartmetz 5y ago
          The information is in the instruction pointer. You jump to the place that deallocates the last resource that was allocated, followed by the second-to-last etc. Also, free(NULL) is not well-defined in C, and other resource types aren't so easy to check. delete nullptr in C++ is well-defined, but you rarely need it.
          • zabzonk 5y ago
            > free(NULL) is not well-defined in C Oh yes it is: https://stackoverflow.com/questions/1938735/does-freeptr-where-ptr-is-null-corrupt-memory https://stackoverflow.com/questions/1938735/does-freeptr-whe...
            • ahartmetz 5y ago
              I stand corrected. So, these days, null checks before free() are just for compatibility with very old systems, or more likely "tradition". I wonder where I got my wrong information? I have even seen null checks before delete in C++ code recently written by C programmers :o
• sys_64738 5y ago
  It's mostly used for error bailing as nested if can be pretty dense to read and error prone.