How to use QtCreator instead of gdb to debug C++ code in an R package based on Rcpp

Question

Context: I have used RStudio on Ubuntu 18.04 to create an hello world R package with C++ code using Rcpp like described here in Rcpp Package Development:

Writing R extensions explains how I can start R with GDB attached for debugging via this shell command:

$ R -d gdb --vanilla

I want to use QtCreator instead of gdb to have debugging GUI, but this doesn't work (just opens a hex dump window and I cannot run R):

$ R -d qtcreator --vanilla

How can I use QtCreator for debugging?

Edit 1:

Attaching the QtCreator debugger to a running R session does not work: If I start R, get the process ID in R via Sys.getpid() and choose Debug > Start Debugging > Attach to running application I get an error:

Edit 2: The ptrace error is caused by kernel hardening that allows only debugging of child processes. I could solve this (temporarily) via

sudo su -
echo 0 > /proc/sys/kernel/yama/ptrace_scope
exit

Still an open issue: The QtCreator debugger shows the assembly code (not the C/C++ code)

Answer 1

Here the steps it takes me to do this using the gdb front end provided by Emacs. As an example, I am debugging a package that uses Rcpp:

1. Open the root directory of the package in Emacs.
2. Start an R session with ESS via M-x R.
3. Get the pid of the R session with Sys.getpid().
4. Start gdb front end with M-x gdb adding -p <pid> to the suggested command line.
5. In gdb add some break point in the package to be loaded. This will be marked as "pending".
6. In gdb continue the R process.
7. In R load the package with devtools::load_all().
8. In R call a function that will reach the break point.
9. In gdb you now have the normal interface but with the Source code being displayed in another buffer. Typically it takes one next step for the source buffer to show.

Here a screen shoot showing the *R* and *gdb* buffers together with the source code. Not the break-point indicated by the red dot and the cursor indicating where processing stands:

If you load the package some other way, e.g. with library(..., lib.loc = "..."), you should open the src directory of the package in the first step. That way Emacs can find the corresponding source file. I expect that this can be transferred to QtCreator as well.