How do you debug a function in a blueprint function library?

I have several blueprint function libraries that I use for utility functions. I’ve noticed that when you set a break point and step into a blueprint library function it that blueprint debugger stops providing watch information. “Debug Filter” at top sets itself to “No debug object selected” and nothing is available in dropdown to select. Is this functionality supported by Unreal, can you watch values in a Blueprint library function using Blueprint Debugger?

Did you have any luck getting this to work? I had it working, but now i can’t debug library functions anymore, same symptoms as ones you described.

I’ve investigated this a little bit, and it seems that setting a breakpoint inside library function won’t let you fully debug anything. You need to break on function call that would enter into library function, then debugging works as normal.

This appears to be not working. I’m having exact problem as initial poster (months later with 4.6.1). I set a break point outside function, and when I step into it, I lose context (and debug filter is No debug object selected, and I can’t pick one).

I did a little more digging and it’s absolutely broken (Blueprint Function Libraries) – from a debugging standpoint, not a functional standpoint.

I had a complex math equation that I placed in it’s own function, and while it lived in a B.F.L., it would not debug – even when you step into it. It always loses debug focus. When I relocated function to a Blueprint’s Function, debugging works as normal. This is using 4.6.1.


After Stepping in

Please fix this, Blueprint Function Libraries are important for global or sharable tech not tied to specific Blueprints. While there is an easy workaround by using something else, without debugging, I will avoid using this.

Basically what I’m doing now is creating a “singleton” blueprint in my scene and attaching functionality into a standard blueprint, but then I need objects to reference it, so it’s not ideal.

I have that same problem ;( Someone found solution for this?

I also just tried getting this to work in 4.7 and I still cannot view values in a function thats part of a BP function library. context is lost. This makes writing complex functions in Blueprint Function Libraries impossible.

Okay so this bug has been around for about a year and it would be nice to hear from a developer on this issue now.

I’m experiencing this issue as well and would appreciate at least a workaround that doesn’t require completely rebuilding my function.

I’m also experiencing this issue.
version 4.7.6

4.8.3 have same problem. For now, only workaround I have is to move function in actor using this function, debug, fix, and bring fix to Blueprint Library function. It can be very long to do it but when you don’t have choice…
Hope it helped

I’ve been having similar issues where debug stops giving live feedback on what blueprint is doing.
Wonder when one of Epic guys is going to comment.

4.9.2 hitting this too. I wonder if this would have better luck in bug report section, staff replies seem to be quicker there.

I created one… [BUG] Cannot Debug a blueprint function - Blueprint - Unreal Engine Forums

Hi all,

We have a bug report open for this issue already (UE-18206) and we’re hoping to resolve it with a large Blueprint Debugger upgrade. There is no timeframe for this currently, however I have added this post to report and increased its community interest level. I’ll track bug report and post here when I see any change in its status.

Correct me if I’m wrong but we’re at 4.15.1 and this still has not been resolved. i.e. still no watch and basic debugging capabilities in blueprint function libraries aside from putting breakpoints without actually being able to track input/output values.
Can anyone catch me up on this?
It’s such a shame since writing libraries is such a healthy powerful practice in any programming language.

4.15.1 still case…


It’s garbage.