We have detected your current browser version is not the latest one. Xilinx.com uses the latest web technologies to bring you the best online experience possible. Please upgrade to a Xilinx.com supported browser:Chrome, Firefox, Internet Explorer 11, Safari. Thank you!

AR# 7817

5.1i CORE Generator - "ERROR: Error locating library for class" occurs after installing IP update


General Description:

After I use UNZIP to extract a CORE Generator IP update to my Xilinx directory, errors similar to the following are reported when I try to call up a core:

"ERROR: Error locating library for class com.xilinx.ip.mult_vgen_v1_0.mult_vgenvht_v1_0GUI.

ERROR: Error loading library for class com.xilinx.ip.mult_vgen_v1_0.mult_vgenvht_v1_0GUI

ERROR: Could not load/define class file com.xilinx.ip.mult_vgen_v1_0.mult_vgenvht_v1_0GUI."


C_IP1.zip, C_IP2.zip, Workstations:

The C_IP1 and C_IP2 updates were originally supplied only as ZIP files. Use of certain later versions of UNZIP to extract these archives on UNIX Workstations may fail because the program lacks support for certain algorithms.

To work around this:

Instead of directly extracting the C_IP1.zip or C_IP2.zip file, extract the .tar.gz file from the Xilinx FTP site at:


PCs (including those running on Novell networks), WorkStations:

This error may be seen if there are older versions of certain data files in your installation. The older files must be removed to eliminate this error.

Try re-installing the latest CORE Generator IP update, available at:


Machines running on Novell networks:

The CORE Generator C_IP updates should not be extracted over Novell networks, and the application should not be installed on a Novell network drive. Novell has an 8.3-character naming restriction on directory and file names, and the directories associated with CORE Generator cores far exceed this limit.

UNIX Workstations:

This problem has also been caused by a system using "gnutar."

When "gnutar" is used to untar the update files, the directories are extracted incorrectly, and file locations are corrupted.

In this case, do not use "gnutar." Use the default tar program provided with the UNIX OS.

In C_IP4 and C_IP5, the following messages may be seen when you try to generate a Virtex Parallel Multiplier:

"ERROR: Error locating library for class com.xilinx.ip.mult_vgen_v1_0.mult_adderstage_vgen_v1_0$virtex.


ERROR: Error loading library for class com.xilinx.ip.mult_vgen_v1_0.mult_adderstage_vgen_v1_0$virtex

ERROR: Could not load/define class file com.xilinx.ip.mult_vgen_v1_0.mult_adderstage_vgen_v1_0$virtex.

ERROR: An internal error has occurred. Please call Xilinx support.

ERROR: Sim has a problem implementing the selected core. Implementation netlist will not be generated.

[Loaded /XILINXM2.1I/coregen/lib/com/xilinx/encore/coregen/exception/GenerateException.class]

ERROR: SimGenerator: Failure of Sim to implement customization parameters core xmult6

WARNING: Core xmult6 did not generate product ImpNetlist."

In the C_IP4 and C_IP5 releases, the Virtex Parallel Multiplier was updated with new data files, but the associated .upd file in $XILINX/coregen/ip was not named correctly.

(NOTE: The .upd file for a core is a temporary, empty file included in an IP update. CORE Generator System 2.1i uses this as a "signal" to update $XILINX/coregen/ip/resources.lib, the CORE Generator table of installed IP. All .upd files are deleted after COREGen starts up and performs the resources.lib update.)

In the C_IP4 and C_IP5 releases, the multiplier .upd file was mistakenly named "mult_vgenvht_v1_0.upd" instead of "mult_vgen_v1_0.upd".

The mismatch between the .upd file name and the actual internal name of the core (as reflected in the core's corresponding subdirectory name) prevents CORE Generator from updating resources.lib with the location of the new files for the multiplier.

To fix this problem with the multiplier, you must:

1. Delete the $XILINX/coregen/ip/resources.lib file so that it can be updated the next time CORE Generator starts up.

2. Delete the $XILINX/coregen/ip/xilinx/mult_vgenvht_v1_0 directory.

3. Install the C_IP5 update.

4. OPTIONAL: Rename the "mult_vgenvht_v1_0.upd" file to "mult_vgen_v1_0.upd" in $XILINX/coregen/ip/xilinx.

5. After doing this, you (or your system administrator, in a networked Workstation environment) must restart the CORE Generator application so that it can recreate $XILINX/coregen/ip/resources.lib. You should then be able to generate the multiplier core.

UNIX Workstation:

1. Write Permission problems

There is a problem with write permissions in the C_IP updates up to and including C_IP4, as well as in D_IP1. Specifically, almost all of the files are installed with read-only permissions.

You can confirm this by typing the following command:

ls -l $XILINX/coregen (Check permissions on the "ip" directory)

ls -lR $XILINX/coregen/ip (Check the permissions on the "xilinx" directory and all underlying directories)

The first group of user permissions for all the files under $XILINX/coregen/ip should have Read and Write access, as shown below by the "rw" designation:

-rw-r--r-- 1 your_admin_name groupname 2307 Jul 5 05:44 <some_filename>

-rw-r--r-- 1 your_admin_name groupname 2307 Jul 5 05:44 <some_filename>

If the permissions instead look like:

-r--r--r-- 1 sysadmin_name groupname 2307 Jul 5 05:44 <some_filename>

-r--r--r-- 1 sysadmin_name groupname 2307 Jul 5 05:44 <some_filename>

you will not be able to update the "coregen/ip" directory properly with the new IP.

To work around this problem, add write permissions on your $XILINX/coregen directory with the following command:

chmod -R u+w $XILINX/coregen

Then, re-install the IP update and restart CORE Generator.

2. Bug in SunOS 5. 6 version of "TAR"

Extracting TAR archives on machines running the following patch version of SunOS 5.6 (Solaris 2.6) causes a problem, as the version of TAR shipped with this patch appends a number to the end of the names of the extracted files:

































This problem was reported in SunOS mic12 5.6 Generic_105181-12 sun4u sparc SUNW,Ultra-1.

It was fixed in SunOS 5.7 (SunOSmic19 5.7 Generic_106541-07 sun4u sparc SUNW,Ultra-5_10).

If none of these resolutions work, uninstall and re-install all Xilinx software, then apply the current IP update.

Be sure to use the appropriate version of the extraction tool, as discussed in (Xilinx Answer 11162).
AR# 7817
Date Created 08/21/2007
Last Updated 07/28/2010
Status Archive
Type General Article