Hello, is there any tools out there for debugging memory leaks and trace dependencies in Nim with GC. For python I use objgraph+graphviz to visualize object dependencies with is extremely useful.
My platform of choice is GNU/Linux. I know/use Valgrind for C projects, but for a nim with GC it is not very useful.
As far as i know Instrumental app is somewhat like valgrind, ie for low level memory allocations. I am actually trying to detect references cycles, and reference inside global variables keeping some objects alive. As such I believe the tool must have knowledge of the Garbage Collector used.
For an example of such tool for python see: objgraph
I was looking for an already existing tool, but that's actually a good idea. Unfortunately I have only vague idea a GC actually works, so I don't think I could modify one to suit my needs. At least without some serious help and a lot of time.
Maybe an idea for a new project.
I have actually used the typeinfo module in the past to access parent type info in inherited types, but I remember it was a bit of a hack.
Ok, so i found a way to view object dependencies in a graph. All the tools already existed :)
First use the compile flag -gc:v2 to switch away from the default GC then at some point call GC_dumpHeap(outfile) to dump the heap content to the file.
In the $NIM_FOLDER/tools/ use the script called heapdump2dot to convert from raw data to dot format. Then use the dot program to output the graph (svg, png or pdf)
heapdump2dot heapdump.txt heapdump.dot | dot -Tsvg -o heapdump.svg
What the ...? Incredible that you found out these things on your own. I was about to write something along the lines. There is also the totally misnamed heapdump2sql tool that gives you a REPL to query the object graph. I found the dot graphs to be overwhelming and useless.
Now please help us to get v2 into production quality. :D
Well, I was combing through lib/system/gc2.nim and found a reference to GC_dumpHeap. From there it wasn't that difficult :)
However I couldn't find a reference to heapdump2sql anywhere in the code. Could you give me more details, it seems very useful. At the very least more than a giant graph. (The last one I extracted was 3500x32000 pixels)
I would be happy to help, especially if we can finally solve this issue. Although v2 does not seems to crash as often.