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AR# 46350

XST - Runs out of stack space even when stack space is set to 32M


A limitation of XST requires a stacksize proportionate to the depth of the design. 

Starting from ISE Design Suite 14.1, XST will generate the following error message if you have a stacksize that is limited:

FATAL_ERROR:Xst:cmain.c:221:1.28 - The XST process ran out of stack space.To avoid this, increase the stack size available with the limit or ulimit shell builtin commands.Refer AR 46350 for more details. Process will terminate. For technical support on this issue, please open a WebCase with this project attached at http://www.xilinx.com/support

This message has been added in 14.1 XST to direct the users to this answer record.


The above message means that the stacksize that is currently set is not sufficient for XST to complete the synthesis process.

The stacksize should be changed to unlimited by using the following commands:

if the shell is sh, bash or ksh use:

ulimit -s unlimited

if the shell is csh, tcsh or zsh use:

limit stacksize unlimited 

Run the following command on the Linux/Unix shell for checking the stacksize:


The output of the above command should resemble the following message:

stacksize unlimited

Now, run XST again and this should fix the FATAL ERROR message. 

If for some reason there is a restriction on the stacksize or XST is running on Windows, then add the following lines to the xst file and run XST again:

set -checkcmdline no
set -use_limited_stack 1

Setting the above variables alters the behavior of XST and can degrade QoR.

The recommended flow is to increase the stacksize.

AR# 46350
Date Created 03/02/2012
Last Updated 10/22/2014
Status Active
Type General Article
  • ISE Design Suite - 13.3