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From: vrm@cathedral.cerc.wvu.wvnet.edu (Vasile R. Montan)
Newsgroups: comp.lang.c
Subject: Error Handling
Keywords: Errors
Message-ID: <837@babcock.cerc.wvu.wvnet.edu>
Date: 27 Sep 90 15:15:21 GMT
Sender: news@cerc.wvu.wvnet.edu
Lines: 65


   Here is a general question to all of the expert C programmers, or
even novice C programmers, who have a strong opinion on C style.  What
is the best way for a function to check for errors and return an error
code?  This sounds like a simple problem, but I don't know which way
to go.  I would just like to follow a style which is easy to maintain.
Below are the methods which I have considered so far.  You may add new
ones if you like.  I apologize for any other style problems in my
example code.  I was trying to make the examples small.

   I will post a summary of all replies that I get through email.

Method 1: Return Error Code When Error Is Encountered
          The problems I have with this are first it goes against
          software engineering principles which say that all functions
          should have one entry point and one exit point.  Secondly
          some functions do have some standard clean up to do.

	  int function()
	  {
	     int error;
             if (error = check1()) {cleanup(); return error;}
             if (error = check2()) {cleanup(); return error;}
             if (error = check3()) {cleanup(); return error;}
	     cleanup();
	     return NOERROR;
          }

Method 2: Set Error Code and Return Only at End
	  The problem I have with this is that I don't want to do
          later work if a previous error occured.  I just want to
          clean up and return.  This forces me to continuously check
          if a previous error occured.

	  int function()
          {
	     int error;
	     error = check1();
	     if (!error) error = check2();
	     if (!error) error = check3();
             cleanup();
             return error;
          }

Method 3: Use GOTO to Create Exception Handler
          Of course this breaks the golden rule of software
          engineering of "absolutely positively no GOTO's in your
          program."

	  int function()
          {
	     int error;
	     if (error = check1()) goto exception;
	     if (error = check2()) goto exception;
	     if (error = check3()) goto exception;
             cleanup();
             return NOERROR;
	  exception:
	     cleanup();
             return error;
          }

Thanks for your time,

-- Vasile