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Path: utzoo!linus!vaxine!wjh12!genrad!decvax!harpo!seismo!hao!hplabs!zehntel!varian!david
From: david@varian.UUCP
Newsgroups: net.wanted,net.unix
Subject: Re: C program error messages
Message-ID: <203@varian.UUCP>
Date: Thu, 12-Apr-84 14:13:08 EST
Article-I.D.: varian.203
Posted: Thu Apr 12 14:13:08 1984
Date-Received: Sat, 14-Apr-84 09:21:32 EST
References: homxa.153
Lines: 113

ho95b!wcs (Bill Stewart) asked if this list, which was posted last year
by Dave Curry, could be reposted or sent to him. I think that it is useful
enough to be reposted. Thanks to Dave Curry for posting it the first time.
	David Brown	 (415) 945-2199
	Varian Instruments 2700 Mitchell Dr.  Walnut Creek, Ca. 94598
	{zehntel,amd70,fortune}!varian!david

=========================

>From zehntel!teklabs!ucbcad!ucbvax:decvax!harpo!npoiv!npois!houxm!ihnp4!ihldt!ll1!otuxa!nwuxc!inuxc!pur-ee!davy Mon Dec  6 18:28:04 1982
Subject: Coredump Message Meanings - Summary - (nf)
Newsgroups: net.lang.c

#N:pur-ee:15500007:000:3266
pur-ee!davy    Dec  6 11:05:00 1982



	This is the information which I have received in response to 
my query about the meanings of the various core dump messages given by 
the shell.  I have summarized much of the information in order to keep 
this article reasonably short (well, 100 lines is shorter than 300....).

------------------

	Bus Error
	    - Types of arguments and parameters don't match.
	    - I/O problems - reading past EOF, reading a closed
	      file, bad file pointers, etc.
		[This refers to stdio only, I think.... --Dave]
	    - Arrays improperly dimensioned.  Eg., attempting to 
	      access a word starting at an odd address.  
	    - Referencing a non-existent bus device.
	    - NULL or unitialized pointer, subscript out of range.

	Memory Fault
	    - Subscripting arrays past the memory allocation for 
	      your program.
	    - NULL or unitialized pointer, subscript out of range.
	    - Attempts to reference data outside valid address space
	    - Parity errors in address space
	    - Recursion (try making your own routines "read" and "write"
	      and then call "scanf" or "printf" and watch what happens).
	
	IOT Trap
	    - Execution of IOT (I/O Trap) instruction; also used by the 
	      "abort" routine (PDP-11's only).

	EMT Trap
	    - Emulator Trap Instruction (PDP-11's).

	Trace/BPT Trap
	    - Execution of the BPT instruction (PDP-11's)
	    - Trace bit set in Processor Status (long)Word
	    - Trying to tell the program to go to an address that
	      doesn't exist.
	    - "Wanton destruction caused execution of data or trashing
	      of instructions."
	    
	Floating Exception
	    - Invalid floating point operation:
		- overflow
		- underflow
		- divide by zero
		- log of negative number
		- float-to-int conversion overflow
	
	Segmentation Fault
	    - Subscript out of range.
	    - Handing "printf", etc. a string which is not NULL
	      terminated.

	Illegal Instruction
	    - Attempt to execute a priviledged instruction, such
	      as "halt".
	    - Execution of nonsense insstruction (e.g., jump to a
	      register).
	    - Forgot -f flag to cc on PDP-11 without floating point 
	      hardware.

	----- Special Note: John Bruner (pur-ee!bruner) also had this
	    to say about Illegal Instruction:

		"On the VAXes the 'abort' routine executes a 'halt' 
		and blows away the program with an illegal instruction.
		Note that SIGTRAP (trace trap) and SIGILL (illegal
		instruction trap) are not reset when caught.  Thus, a
		generalized trap handler such as

			sig(s)
			int s;
			{
			    fprintf(stderr, "Fatal signal %d\n", sig);
			    abort();
			}
		
		will (on the VAX) recursively call 'abort' which will 
		attempt to execute a 'halt' [illegal] and trap to 'sig'
		which will call 'abort'... until you either kill it 
		with a signal it doesn't catch (e.g. SIGKILL=9) or it
		runs out of stack space (a LONG time on the VAX)."
	

------------------

	In all, I got 5 responses with information about the messages,
and three responses asking for a copy of the summary (to those of you
who asked, I have sent you each a copy via mail).  Thanks go to all
who responded: John Bruner (pur-ee!bruner), arizona!tom, ihuxw!thor, 
Bob Van Valzah (tpdcvax!bobvan), Geoff Collyer (utcsstat!geoff).

--Dave Curry
pur-ee!davy