Path: utzoo!utgpu!news-server.csri.toronto.edu!rpi!usc!ucsd!ucbvax!CANNON.CS.USU.EDU!scott
From: scott@CANNON.CS.USU.EDU (Scott Cannon)
Newsgroups: comp.sys.transputer
Subject: quirk in LSC
Message-ID: <9105161454.AA06109@cannon.cs.usu.edu>
Date: 16 May 91 14:54:51 GMT
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  Here's an interesting quirk of LSC 89.1 pointed out to me by a graduate student.  Consider the following trivial program:

	#include <stdlib.h>
	#define N ...
	main ()
	 { int x[N];
	   printf (" success\n");
	 }

  When N is defined as 1010 or more, the program runs fine.  When N is defined as less than 970, the program runs fine.  When N is define between 970 and 1010, the program produces garbage or hangs.  

  Since x is declared as local to main, it will be placed on the stack.  With a default stack space of 4k, it is easy to see why an array size larger than 1000 would max out the run-time stack.  What is confusing is why LARGER arrays seem to produce no problems!  This example program is a simplification of a more complex program in which the quirk was first noticed.  My guess is that a test is made concerning array allocations during compilation -- when an array is larger than stack space, it is moved to s





tatic memory or the default stacksize is increased.  (Either that or example programs with large arrays have all been extremely lucky).  Some feature of the test fails when the array size is nearly 4k or (int x[970]) to (int x[1010]).

Scott R. Cannon, PhD            scott@cannon.cs.usu.edu
Dept. of Computer Science       (801) 750-2015
Utah State Univ.                FAX (801) 750-3378
Logan, UT.  84322-4205