std::bad_alloc exception running Q# code from Python

[bettinaheim]

Describe the bug

This is a bug report. I’m calling a toy Q# example repeatedly using the python wrappers, which results in an exception.
The source code that triggers the issue on my workstation is the following:
/*********** bug.qs */
namespace Microsoft.Bug
{
open Microsoft.Quantum.Intrinsic;
// open Microsoft.Quantum.Canon;
operation Set (desired: Result, q1: Qubit) : Unit {
if (desired != M(q1)) {
X(q1);
}
}
operation main() : Unit
{
using ((a, b, c) = (Qubit8, Qubit8, Qubit8))
{
}
}
}
/ end of bug.qs /
/ bug.py */
import qsharp
from Microsoft.Bug import main
for _ in range(256):
main.simulate()
print(_)
/ end of bug.py /
Calling python3 bug.py results in the following (abridged) output:
/ output ****/
1
2
…
40
41
terminate called after throwing an instance of ‘std::bad_alloc’
what(): std::bad_alloc
/ end of output ********/
Python then stops producing output. Removing the definition of Set (desired: Result, q1: Qubit) : Unit
from bug.qs results in python slowing down as the 42th iteration approaches, and then hanging (without
exception as far as I could see).
My machine is a Virtualbox 6.0.8 VM. My dotnet info is as follows:
$ dotnet iqsharp —version
Language kernel: 0.6.1905.301
Jupyter core: 1.1.13141.0
$ dotnet —info
.NET Core SDK (reflecting any global.json):
Version: 2.2.300
Commit: 73efd5bd87
Runtime Environment:
OS Name: ubuntu
OS Version: 18.04
OS Platform: Linux
RID: ubuntu.18.04-x64
Base Path: /usr/share/dotnet/sdk/2.2.300/
Host (useful for support):
Version: 2.2.5
Commit: 0a3c9209c0
.NET Core SDKs installed:
2.2.300 [/usr/share/dotnet/sdk]
.NET Core runtimes installed:
Microsoft.AspNetCore.All 2.2.5 [/usr/share/dotnet/shared/Microsoft.AspNetCore.All]
Microsoft.AspNetCore.App 2.2.5 [/usr/share/dotnet/shared/Microsoft.AspNetCore.App]
Microsoft.NETCore.App 2.2.5 [/usr/share/dotnet/shared/Microsoft.NETCore.App]
To install additional .NET Core runtimes or SDKs:
https://aka.ms/dotnet-download
I’m happy to run further tests if needed.
Cheers
Fernando

Additional context
Transferred over from User Voice

[anpaz]

Was not able to reproduce this running locally with:

• iq#: 0.8.1907.1701
• .net core: 2.2.401
• Python: 3.7.0

and on binder with:
{'iqsharp': LooseVersion ('0.8.1907.1701'),
'Jupyter Core': LooseVersion ('1.1.14623.0'),
'qsharp': LooseVersion ('0.8.1907.1701')}

Ran it multiple times, all successfully finished all iterations. Never seen it before, suspect something on the environment.. Closing this issue, let us know if you can reproduce it.