如何构建具有许多故障点的代码? [英] How to structure code with many failure points?

问题描述

我有一段代码可能会在很多时候失败.每增加一个动作(也可能失败)，可读性就会变差.有没有更好的方法来构造它?有没有针对此的设计模式?

I have a piece of code that can fail at many points. With each additional action (that can also fail), the readability worsens. Is there a better way to structure this? Is there a design pattern for this?

int32_t InitializeMyThingy(void) {
  int32_t retcode;

  retcode = DoA();
  if (retcode != 0) return retcode;
  retcode = DoB();
  if (retcode != 0) return retcode;
  retcode = DoC();
  if (retcode != 0) return retcode;
  retcode = DoD();

  return retcode;
}

或者(更易读?):

int32_t InitializeMyThingy(void) {
  int32_t retcode;

  retcode = DoA();
  if (0 == retcode) {
    retcode = DoB();
    if (0 == retcode) {
      retcode = DoC();
      if (0 == retcode) {
        retcode = DoD();
      }
    }
  }

  return retcode;
}

推荐答案

在 C 中，带有 goto 的 SESE(单入口，单出口)模式通常是合适的:

In C, a SESE (single entry, single exit) pattern with goto is usually appropriate:

int32_t InitializeMyThingy(void) {
  int32_t retcode;

  retcode = DoA();
  if (retcode != 0) goto exit;
  retcode = DoB();
  if (retcode != 0) goto exit;
  retcode = DoC();
  if (retcode != 0) goto exit;
  retcode = DoD();

exit:
  return retcode;
}

就其本身而言，这与在每次检查后具有 return 语句的第一个示例没有任何不同.但是一旦您的代码开始分配资源，goto 方法就会更加简洁:

By itself, this isn't any different from your first example that has return statements after each check. But once you your code starts allocating resources, the goto approach is much cleaner:

int32_t InitializeMyThingy(void) {
  int32_t retcode = E_FAIL;
  A* a = NULL;
  B* b = NULL;
  C* c = NULL;

  a = AllocateA();
  if (a == NULL) goto exit;

  b = AllocateB(a);
  if (b == NULL) goto exit;

  c = AllocateC(b);
  if (c == NULL) goto exit;

  retcode = DoSomething(c);

exit:
  free(c);
  free(b);
  free(a);
  return retcode;
}

现在您不必担心在每个出口点确定要清理的内容.

and now you don't have to worry about figuring out what to clean up at every individual exit point.

尽管许多反对者对 goto 持反对意见，但如果使用得当，它是 C 中最明智的错误处理形式.

Despite what many naysayers say about goto, when used properly, it is the sanest form of error-handling in C.

关于添加额外动作的可读性，我认为用空格分隔动作有很大帮助.或者，如果您真的想要紧凑性，您可以考虑执行内联操作和错误检查:

Regarding readability from adding additional actions, I think separating actions with whitespace helps a lot. Or, if you really want compactness, you could consider doing the action and the error check inline:

if ((retcode = DoA()) != 0) goto exit;

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