cgraph | computational graph engine

File descriptors and file pointers are not the same thing. It's confusing, and made even more frustrating by the fact that FILE * is really hard to Google because of the symbol.

You need to fdopen the file descriptor (pipe.fileHandleForWriting.fileDescriptor), to receive a FILE * (UnsafeMutablePointer in Swift). This is what you then pass to agwrite.

It's important to fclose the file pointer when you're done writing to it, otherwise .readDataToEndOfFile() will never terminate. I made a helper function to ensure the fclose can't be forgetten. It's possible that agwrite closes the file pointer itself, internally. If that's the case, you should delete this code and just give it the result of fdopen, plain and simple.

Here is an example. I assume a function use_struct() is defined in a library libslib :

Also ran into this problem just now, found in another question the answer

To summarize here:

From PyGraphviz documentation - To use PyGraphviz you need Python version 2.6.x or 2.7.x.

PyGraphviz does not work with Python 3

link to more info.

As you are using Anaconda3, you are using Python 3.

In the comments of the answer there is also a work-around but I have yet to try it.

Finally got it working:

You can use the function agnameof, which is listed in the "Generic Objects" section of the cgraph manpage:

When I try to stepi my way through I get this:

The problem is that you are stepping into the code inside dynamic loader -- code responsible for resolving imported symbols, such as gvNextInputGraph@plt to their definition in a shared library.

The code in dynamic loader lacks debug info (and is not the code you want to be stepping through anyway).

Several ways around this:

1. Don't use stepi, use step (this will stop inside the called function).
2. Use step the first time you encounter this function. After the first time, the function will have been resolved, and you can use stepi.
3. Set LD_BIND_NOW=1 in the environment. This will cause dynamic loader to resolve all the symbols at startup time, so by the time you execute your stepis, the symbol will already be resolved.
4. Build your executable without shared libraries (so that everything is linked into the main binary) -- the loader will then have nothing to resolve.

Update:

I only answered the "why is stepi weird" part of the question, but your main question is "why aren't breakpoints getting set".

The answer is: your build of libgvc.so.6 (where you are trying to set breakpoints) is missing debug info.

There are two likely possibilities:

1. You are debugging system provided version in /usr/lib/ rather than the version you built, or
2. When you do make install, the library is stripped.

To fix #1, use LD_LIBRARY_PATH to point to your own version. To fix #2, use the "as built" version using LD_LIBRARY_PATH (i.e. same as above), or change Makefile to not strip. Running

Turned out that i changed API version of ASM and the signature of MethodVisitor.visitMethodInsn is different between versions 4 and 5. The dynamic binding no longer recognized it as an overriding method.

I could fix this by adding the missing parameters to InvokeFinder.visitMethodInsn, whose signature now is

You need to link in graphviz library using target_link_libraries(Learning path/to/graphviz.so).