[BUG] Forwarding of Empty Arguments to Profiled Application

[chriswasser]

Hi Thomas,

Sorry to open a bug report this close to the weekend and especially around Christmas 🎄 There might be a minor bug which has floated around for quite some time.

Describe the bug
LIKWID's CLI parsing does not correctly forward all empty arguments to the profiled application. An empty argument is only passed on correctly if it is the very last argument in the argument list. I only tested this behaviour for likwid-perfctr although this bug might be present in other LIKWID tools as well due to the shared code base.

To Reproduce
The following shell commands act as a reproducer and use taskset's argument forwarding as a reference:

: > test.sh
chmod +x test.sh
cat >> test.sh <<EOF
echo "Number of Arguments: \${#}"
for argument in "\${@}"; do
    echo "--> '\${argument}'"
done
EOF

echo 'Running taskset...'
taskset -c 0 test.sh -a '' -b '' -c ''
taskset -c 0 test.sh -a '' -b '' -c 'argument'

echo 'Running likwid-perfctr...'
likwid-perfctr -C 0 -g MEM -o output.txt -- test.sh -a '' -b '' -c ''
likwid-perfctr -C 0 -g MEM -o output.txt -- test.sh -a '' -b '' -c 'argument'

rm -f test.sh output.txt

We can see that LIKWID deviates from taskset's behaviour in the resulting output:

Running taskset...
Number of Arguments: 6
--> '-a'
--> ''
--> '-b'
--> ''
--> '-c'
--> ''
Number of Arguments: 6
--> '-a'
--> ''
--> '-b'
--> ''
--> '-c'
--> 'argument'
Running likwid-perfctr...
Number of Arguments: 4
--> '-a'
--> '-b'
--> '-c'
--> ''
Number of Arguments: 4
--> '-a'
--> '-b'
--> '-c'
--> 'argument'

This was tested with the following LIKWID version:

$ likwid-perfctr -v
likwid-perfctr -- Version 5.0.2 (commit: 233ab943543480cd46058b34616c174198ba0459)

OS version (probably not relevant):

$ lsb_release -a
LSB Version:    :core-4.1-amd64:core-4.1-noarch
Distributor ID: CentOS
Description:    CentOS Linux release 7.8.2003 (Core)
Release:        7.8.2003
Codename:       Core

The bug is not specific to an application.
The bug is not specific to a hardware architecture.
The bug is not associated with GPUs
The bug is not associated with the MarkerAPI.

To Reproduce with a LIKWID command
If you need the complete output of likwid-perfctr with -V 3, I can supply the full output. But since the bug is not associated to the perfmon infrastructure, I have only pasted the relevant parts below:

Running taskset...
Number of Arguments: 6
--> '-a'
--> ''
--> '-b'
--> ''
--> '-c'
--> ''
Number of Arguments: 6
--> '-a'
--> ''
--> '-b'
--> ''
--> '-c'
--> 'argument'
# start LIKWID debug output
Running likwid-perfctr...
# more LIKWID debug output
Executing: test.sh -a  -b  -c 
# more LIKWID debug output
Number of Arguments: 4
--> '-a'
--> '-b'
--> '-c'
--> ''
# more LIKWID debug output
# start LIKWID debug output
Executing: test.sh -a  -b  -c argument
# more LIKWID debug output
Number of Arguments: 4
--> '-a'
--> '-b'
--> '-c'
--> 'argument'
# more LIKWID debug output

Additional context
I suspect that the bug occurs due to the interaction of these three parts of the code:

• https://github.com/RRZE-HPC/likwid/blob/v5.0/src/applications/likwid-perfctr.lua#L382-L385
• https://github.com/RRZE-HPC/likwid/blob/v5.0/src/applications/likwid-perfctr.lua#L905
• https://github.com/RRZE-HPC/likwid/blob/v5.0/src/luawid.c#L1945-L1957

However, you probably know best where to look 👍 Hope the descriptions helps in bug hunting nevertheless 🐛

Greetings,

Christian

Edit: Also verified that the same bug occurs for the latest 5.1.0 LIKWID release

[TomTheBear]

Hi Christian,

Thanks for finding this and supplying detailed information. I'll look into it.

Best,
Thomas

[TomTheBear]

I looked into it and you were on the right track. It's a combination of joining the string and parsing of the argument list.

[chriswasser]

Can confirm that the fix pushed to the empty_cli_args branch fixes this issue 👌
Other tests with nested quotes as arguments ("''" or '""') also work fine 👍
Thanks Thomas 🎉

[TomTheBear]

Thanks for testing and confirming the fix.