KCachegrind Cannot Display Control Flow Graph Despite dot Installed and Working on WSL2

Question

I'm having trouble visualizing the control flow graph in KCachegrind when analyzing my callgrind output. Although I have both dot (GraphViz) and objdump installed and working, KCachegrind fails to display the control flow graph and shows an error related to the dot process (I think). Below are all relevant details about my setup, troubleshooting steps, and outputs.

OS: WSL2

$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description:    Ubuntu 20.04.6 LTS
Release:        20.04
Codename:       focal

KCachegrind version

$ kcachegrind --version
kcachegrind 25.04.1

Dot version

$ dot -V
dot - graphviz version 2.43.0 (0)

I tried testing dot directly:

echo "digraph G { A -> B }" | dot -Tpng -o test.png
# test.png was created successfully

Checked /tmp persmissions:

$ ls -ld /tmp
drwxrwxrwt 9 root root 12288 Jun  9 14:39 /tmp

When running kcachegrind the control flow graph is not displayed, it only shows the text

No graph available because the layouting process failed. Trying to run the following command did not work dot -Tplain-ext
Please check that dot is installed.

I tried running this command by myself and it seems to also work:

$ dot -Tplain-ext test.dot
graph 1 1.125 2.5
node A 0.75 2.25 0.75 0.5 A solid ellipse black lightgrey
node B 0.375 1.25 0.75 0.5 B solid ellipse black lightgrey
node C 0.75 0.25 0.75 0.5 C solid ellipse black lightgrey
edge A B 4 0.66113 2.0057 0.61787 1.8935 0.56481 1.756 0.51619 1.6299 solid black
edge B C 4 0.46387 1.0057 0.50713 0.89354 0.56019 0.75599 0.60881 0.62993 solid black
edge C A 10 0.80075 0.50128 0.82883 0.64488 0.86084 0.83208 0.875 1 0.89367 1.2214 0.89367 1.2786 0.875 1.5 0.86505 1.6181 0.84626 1.7457 0.82623 1.8609 solid black
stop

The output when running kcachegrind is the following:

$ kcachegrind callgrind_original.out.55340
Selected  "main"
ControlFlowGraphView::refresh: Starting process  QProcess(0x566cd5d2b660) , ' QProcess(0x566cd5d2b660) '
Running 'objdump -C -d --start-address=0x11E0 --stop-address=0x201A /home/user/prog/test/real'...
ControlFlowGraphView::dotError: Got  QProcess::WriteError  from QProcess  QProcess(0x566cd5d2b660)
QProcess: Destroyed while process ("dot") is still running.
ControlFlowGraphView::dotExited: QProcess  QProcess(0x566cd5d2b660)

I tried running kcachegrind as root, but then I get into a different issue:

$ sudo kcachegrind callgrind_original.out.55340
kf.dbusaddons: DBus session bus not found. To circumvent this problem try the following command (with bash):
    export $(dbus-launch)

I get this error always when running it as root also when I tried the export.

What could be causing this problem, and how can I get KCachegrind to display the control flow graph?

Can you run kcachegrind on a real OS rather than ujsing virtualisation? — Paul Floyd
– Paul Floyd, Commented Jun 9 at 19:10

sroush · Accepted Answer · 2025-06-09 21:14:38Z

0

[This is a guess]
As "you" (i.e. not as root)

Uname=`id -nu`
Uno=`id -u`
echo "the id command says I am:   $Uname $Uno"

ls -l /run/user/$Uno

is there a directory named /run/user/$Uno ???
are the permissions at least "drwxr--r--" (744)
if not, "sudo su" and make it so

answered Jun 9 at 21:14

sroush

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